Merge pull request #1625 from jzhou77/backup-worker

Create a backup role in the cluster

fdbbackup/CMakeLists.txt

@@ -4,6 +4,18 @@ set(FDBBACKUP_SRCS
 add_flow_target(EXECUTABLE NAME fdbbackup SRCS ${FDBBACKUP_SRCS})
 target_link_libraries(fdbbackup PRIVATE fdbclient)
 
+set(FDBCONVERT_SRCS
+	FileConverter.actor.cpp
+	FileConverter.h)
+add_flow_target(EXECUTABLE NAME fdbconvert SRCS ${FDBCONVERT_SRCS})
+target_link_libraries(fdbconvert PRIVATE fdbclient)
+
+set(FDBDECODE_SRCS
+	FileDecoder.actor.cpp
+	FileConverter.h)
+add_flow_target(EXECUTABLE NAME fdbdecode SRCS ${FDBDECODE_SRCS})
+target_link_libraries(fdbdecode PRIVATE fdbclient)
+
 if(NOT OPEN_FOR_IDE)
   fdb_install(TARGETS fdbbackup DESTINATION bin COMPONENT clients)
   install_symlink(

fdbbackup/FileConverter.actor.cpp

@@ -0,0 +1,596 @@
+/*
+ * FileConverter.actor.cpp
+ *
+ * This source file is part of the FoundationDB open source project
+ *
+ * Copyright 2013-2019 Apple Inc. and the FoundationDB project authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "fdbbackup/FileConverter.h"
+
+#include <algorithm>
+#include <iostream>
+#include <cinttypes>
+#include <cstdio>
+#include <vector>
+
+#include "fdbclient/BackupAgent.actor.h"
+#include "fdbclient/BackupContainer.h"
+#include "fdbclient/MutationList.h"
+#include "flow/flow.h"
+#include "flow/serialize.h"
+
+namespace file_converter {
+
+void printConvertUsage() {
+	std::cout << "\n"
+	          << "  -r, --container Container URL.\n"
+	          << "  -b, --begin BEGIN\n"
+	          << "                  Begin version.\n"
+	          << "  -e, --end END   End version.\n"
+	          << "  --log           Enables trace file logging for the CLI session.\n"
+	          << "  --logdir PATH   Specifes the output directory for trace files. If\n"
+	          << "                  unspecified, defaults to the current directory. Has\n"
+	          << "                  no effect unless --log is specified.\n"
+	          << "  --loggroup LOG_GROUP\n"
+	          << "                  Sets the LogGroup field with the specified value for all\n"
+	          << "                  events in the trace output (defaults to `default').\n"
+	          << "  --trace_format FORMAT\n"
+	          << "                  Select the format of the trace files. xml (the default) and json are supported.\n"
+	          << "                  Has no effect unless --log is specified.\n"
+	          << "  -h, --help      Display this help and exit.\n"
+	          << "\n";
+
+	return;
+}
+
+void printLogFiles(std::string msg, const std::vector<LogFile>& files) {
+	std::cout << msg << " " << files.size() << " log files\n";
+	for (const auto& file : files) {
+		std::cout << file.toString() << "\n";
+	}
+	std::cout << std::endl;
+}
+
+std::vector<LogFile> getRelevantLogFiles(const std::vector<LogFile>& files, Version begin, Version end) {
+	std::vector<LogFile> filtered;
+	for (const auto& file : files) {
+		if (file.beginVersion <= end && file.endVersion >= begin && file.tagId >= 0) {
+			filtered.push_back(file);
+		}
+	}
+	std::sort(filtered.begin(), filtered.end());
+
+	// Remove duplicates. This is because backup workers may store the log for
+	// old epochs successfully, but do not update the progress before another
+	// recovery happened.	As a result, next epoch will retry and creates
+	// duplicated log files.
+	std::vector<LogFile> sorted;
+	int i = 0;
+	for (int j = 1; j < filtered.size(); j++) {
+		if (!filtered[i].sameContent(filtered[j])) {
+			sorted.push_back(filtered[i]);
+			i = j;
+		}
+	}
+	if (i < filtered.size()) {
+		sorted.push_back(filtered[i]);
+	}
+
+	return sorted;
+}
+
+struct ConvertParams {
+	std::string container_url;
+	Version begin = invalidVersion;
+	Version end = invalidVersion;
+	bool log_enabled = false;
+	std::string log_dir, trace_format, trace_log_group;
+
+	bool isValid() { return begin != invalidVersion && end != invalidVersion && !container_url.empty(); }
+
+	std::string toString() {
+		std::string s;
+		s.append("ContainerURL:");
+		s.append(container_url);
+		s.append(" Begin:");
+		s.append(format("%" PRId64, begin));
+		s.append(" End:");
+		s.append(format("%" PRId64, end));
+		if (log_enabled) {
+			if (!log_dir.empty()) {
+				s.append(" LogDir:").append(log_dir);
+			}
+			if (!trace_format.empty()) {
+				s.append(" Format:").append(trace_format);
+			}
+			if (!trace_log_group.empty()) {
+				s.append(" LogGroup:").append(trace_log_group);
+			}
+		}
+		return s;
+	}
+};
+
+struct VersionedData {
+	LogMessageVersion version;
+	StringRef message; // Serialized mutation.
+	Arena arena; // The arena that contains mutation.
+
+	VersionedData() : version(invalidVersion, -1) {}
+	VersionedData(LogMessageVersion v, StringRef m, Arena a) : version(v), message(m), arena(a) {}
+};
+
+struct MutationFilesReadProgress : public ReferenceCounted<MutationFilesReadProgress> {
+	MutationFilesReadProgress(std::vector<LogFile>& logs, Version begin, Version end)
+	  : files(logs), beginVersion(begin), endVersion(end) {}
+
+	struct FileProgress : public ReferenceCounted<FileProgress> {
+		FileProgress(Reference<IAsyncFile> f, int index) : fd(f), idx(index), offset(0), eof(false) {}
+
+		bool operator<(const FileProgress& rhs) const {
+			if (rhs.mutations.empty()) return true;
+			if (mutations.empty()) return false;
+			return mutations[0].version < rhs.mutations[0].version;
+		}
+		bool operator<=(const FileProgress& rhs) const {
+			if (rhs.mutations.empty()) return true;
+			if (mutations.empty()) return false;
+			return mutations[0].version <= rhs.mutations[0].version;
+		}
+		bool empty() { return eof && mutations.empty(); }
+
+		// Decodes the block into mutations and save them if >= minVersion and < maxVersion.
+		// Returns true if new mutations has been saved.
+		bool decodeBlock(const Standalone<StringRef>& buf, int len, Version minVersion, Version maxVersion) {
+			StringRef block(buf.begin(), len);
+			StringRefReader reader(block, restore_corrupted_data());
+			int count = 0, inserted = 0;
+			Version msgVersion = invalidVersion;
+
+			try {
+				while (1) {
+					// If eof reached or first key len bytes is 0xFF then end of block was reached.
+					if (reader.eof() || *reader.rptr == 0xFF) break;
+
+					// Deserialize messages written in saveMutationsToFile().
+					msgVersion = bigEndian64(reader.consume<Version>());
+					uint32_t sub = bigEndian32(reader.consume<uint32_t>());
+					int msgSize = bigEndian32(reader.consume<int>());
+					const uint8_t* message = reader.consume(msgSize);
+
+					BinaryReader rd(message, msgSize, AssumeVersion(currentProtocolVersion));
+					MutationRef m;
+					rd >> m;
+					count++;
+					if (msgVersion >= maxVersion) {
+						TraceEvent("FileDecodeEnd")
+						    .detail("MaxV", maxVersion)
+						    .detail("Version", msgVersion)
+						    .detail("File", fd->getFilename());
+						eof = true;
+						break; // skip
+					}
+					if (msgVersion >= minVersion) {
+						mutations.emplace_back(LogMessageVersion(msgVersion, sub), StringRef(message, msgSize),
+						                       buf.arena());
+						inserted++;
+					}
+				}
+				offset += len;
+
+				TraceEvent("Decoded")
+				    .detail("Name", fd->getFilename())
+				    .detail("Count", count)
+				    .detail("Insert", inserted)
+				    .detail("BlockOffset", reader.rptr - buf.begin())
+				    .detail("Total", mutations.size())
+				    .detail("EOF", eof)
+				    .detail("Version", msgVersion)
+				    .detail("NewOffset", offset);
+				return inserted > 0;
+			} catch (Error& e) {
+				TraceEvent(SevWarn, "CorruptLogFileBlock")
+				    .error(e)
+				    .detail("Filename", fd->getFilename())
+				    .detail("BlockOffset", offset)
+				    .detail("BlockLen", len)
+				    .detail("ErrorRelativeOffset", reader.rptr - buf.begin())
+				    .detail("ErrorAbsoluteOffset", reader.rptr - buf.begin() + offset);
+				throw;
+			}
+		}
+
+		Reference<IAsyncFile> fd;
+		int idx; // index in the MutationFilesReadProgress::files vector
+		int64_t offset; // offset of the file to be read
+		bool eof; // If EOF is seen so far or endVersion is encountered. If true, the file can't be read further.
+		std::vector<VersionedData> mutations; // Buffered mutations read so far
+	};
+
+	bool hasMutations() {
+		for (const auto& fp : fileProgress) {
+			if (!fp->empty()) return true;
+		}
+		return false;
+	}
+
+	void dumpProgress(std::string msg) {
+		std::cout << msg << "\n  ";
+		for (const auto fp : fileProgress) {
+			std::cout << fp->fd->getFilename() << " " << fp->mutations.size() << " mutations";
+			if (fp->mutations.size() > 0) {
+				std::cout << ", range " << fp->mutations[0].version.toString() << " "
+				          << fp->mutations.back().version.toString() << "\n";
+			} else {
+				std::cout << "\n\n";
+			}
+		}
+	}
+
+	// Sorts files according to their first mutation version and removes files without mutations.
+	void sortAndRemoveEmpty() {
+		std::sort(fileProgress.begin(), fileProgress.end(),
+		          [](const Reference<FileProgress>& a, const Reference<FileProgress>& b) { return (*a) < (*b); });
+		while (!fileProgress.empty() && fileProgress.back()->empty()) {
+			fileProgress.pop_back();
+		}
+	}
+
+	// Requires hasMutations() return true before calling this function.
+	// The caller must hold on the the arena associated with the mutation.
+	Future<VersionedData> getNextMutation() { return getMutationImpl(this); }
+
+	ACTOR static Future<VersionedData> getMutationImpl(MutationFilesReadProgress* self) {
+		ASSERT(!self->fileProgress.empty() && !self->fileProgress[0]->mutations.empty());
+
+		state Reference<FileProgress> fp = self->fileProgress[0];
+		state VersionedData data = fp->mutations[0];
+		fp->mutations.erase(fp->mutations.begin());
+		if (fp->mutations.empty()) {
+			// decode one more block
+			wait(decodeToVersion(fp, /*version=*/0, self->endVersion, self->getLogFile(fp->idx)));
+		}
+
+		if (fp->empty()) {
+			self->fileProgress.erase(self->fileProgress.begin());
+		} else {
+			// Keep fileProgress sorted
+			for (int i = 1; i < self->fileProgress.size(); i++) {
+				if (*self->fileProgress[i - 1] <= *self->fileProgress[i]) {
+					break;
+				}
+				std::swap(self->fileProgress[i - 1], self->fileProgress[i]);
+			}
+		}
+		return data;
+	}
+
+	LogFile& getLogFile(int index) { return files[index]; }
+
+	Future<Void> openLogFiles(Reference<IBackupContainer> container) { return openLogFilesImpl(this, container); }
+
+	// Opens log files in the progress and starts decoding until the beginVersion is seen.
+	ACTOR static Future<Void> openLogFilesImpl(MutationFilesReadProgress* progress,
+	                                           Reference<IBackupContainer> container) {
+		state std::vector<Future<Reference<IAsyncFile>>> asyncFiles;
+		for (const auto& file : progress->files) {
+			asyncFiles.push_back(container->readFile(file.fileName));
+		}
+		wait(waitForAll(asyncFiles)); // open all files
+
+		// Attempt decode the first few blocks of log files until beginVersion is consumed
+		std::vector<Future<Void>> fileDecodes;
+		for (int i = 0; i < asyncFiles.size(); i++) {
+			Reference<FileProgress> fp(new FileProgress(asyncFiles[i].get(), i));
+			progress->fileProgress.push_back(fp);
+			fileDecodes.push_back(
+			    decodeToVersion(fp, progress->beginVersion, progress->endVersion, progress->getLogFile(i)));
+		}
+
+		wait(waitForAll(fileDecodes));
+
+		progress->sortAndRemoveEmpty();
+
+		return Void();
+	}
+
+	// Decodes the file until EOF or an mutation >= minVersion and saves these mutations.
+	// Skip mutations >= maxVersion.
+	ACTOR static Future<Void> decodeToVersion(Reference<FileProgress> fp, Version minVersion, Version maxVersion,
+	                                          LogFile file) {
+		if (fp->empty()) return Void();
+
+		if (!fp->mutations.empty() && fp->mutations.back().version.version >= minVersion) return Void();
+
+		try {
+			// Read block by block until we see the minVersion
+			loop {
+				state int64_t len = std::min<int64_t>(file.blockSize, file.fileSize - fp->offset);
+				if (len == 0) {
+					fp->eof = true;
+					return Void();
+				}
+
+				state Standalone<StringRef> buf = makeString(len);
+				int rLen = wait(fp->fd->read(mutateString(buf), len, fp->offset));
+				if (len != rLen) throw restore_bad_read();
+
+				TraceEvent("ReadFile")
+				    .detail("Name", fp->fd->getFilename())
+				    .detail("Length", rLen)
+				    .detail("Offset", fp->offset);
+				if (fp->decodeBlock(buf, rLen, minVersion, maxVersion)) break;
+			}
+			return Void();
+		} catch (Error& e) {
+			TraceEvent(SevWarn, "CorruptedLogFileBlock")
+			    .error(e)
+			    .detail("Filename", fp->fd->getFilename())
+			    .detail("BlockOffset", fp->offset)
+			    .detail("BlockLen", len);
+			throw;
+		}
+	}
+
+	std::vector<LogFile> files;
+	const Version beginVersion, endVersion;
+	std::vector<Reference<FileProgress>> fileProgress;
+};
+
+// Writes a log file in the old backup format, described in backup-dataFormat.md.
+// This is similar to the LogFileWriter in FileBackupAgent.actor.cpp.
+struct LogFileWriter {
+	LogFileWriter() : blockSize(-1) {}
+	LogFileWriter(Reference<IBackupFile> f, int bsize) : file(f), blockSize(bsize) {}
+
+	// Returns the block key, i.e., `Param1`, in the back file. The format is
+	// `hash_value|commitVersion|part`.
+	static Standalone<StringRef> getBlockKey(Version commitVersion, int part) {
+		const int32_t version = commitVersion / CLIENT_KNOBS->LOG_RANGE_BLOCK_SIZE;
+
+		BinaryWriter wr(Unversioned());
+		wr << (uint8_t)hashlittle(&version, sizeof(version), 0);
+		wr << bigEndian64(commitVersion);
+		wr << bigEndian32(part);
+		return wr.toValue();
+	}
+
+	// Return a block of contiguous padding bytes, growing if needed.
+	static Value makePadding(int size) {
+		static Value pad;
+		if (pad.size() < size) {
+			pad = makeString(size);
+			memset(mutateString(pad), '\xff', pad.size());
+		}
+
+		return pad.substr(0, size);
+	}
+
+	// Start a new block if needed, then write the key and value
+	ACTOR static Future<Void> writeKV_impl(LogFileWriter* self, Key k, Value v) {
+		// If key and value do not fit in this block, end it and start a new one
+		int toWrite = sizeof(int32_t) + k.size() + sizeof(int32_t) + v.size();
+		if (self->file->size() + toWrite > self->blockEnd) {
+			// Write padding if needed
+			int bytesLeft = self->blockEnd - self->file->size();
+			if (bytesLeft > 0) {
+				state Value paddingFFs = makePadding(bytesLeft);
+				wait(self->file->append(paddingFFs.begin(), bytesLeft));
+			}
+
+			// Set new blockEnd
+			self->blockEnd += self->blockSize;
+
+			// write Header
+			wait(self->file->append((uint8_t*)&BACKUP_AGENT_MLOG_VERSION, sizeof(BACKUP_AGENT_MLOG_VERSION)));
+		}
+
+		wait(self->file->appendStringRefWithLen(k));
+		wait(self->file->appendStringRefWithLen(v));
+
+		// At this point we should be in whatever the current block is or the block size is too small
+		if (self->file->size() > self->blockEnd) throw backup_bad_block_size();
+
+		return Void();
+	}
+
+	Future<Void> writeKV(Key k, Value v) { return writeKV_impl(this, k, v); }
+
+	// Adds a new mutation to an interal buffer and writes out when encountering
+	// a new commitVersion or exceeding the block size.
+	ACTOR static Future<Void> addMutation(LogFileWriter* self, Version commitVersion, MutationListRef mutations) {
+		state Standalone<StringRef> value = BinaryWriter::toValue(mutations, IncludeVersion());
+
+		state int part = 0;
+		for (; part * CLIENT_KNOBS->MUTATION_BLOCK_SIZE < value.size(); part++) {
+			StringRef partBuf = value.substr(
+			    part * CLIENT_KNOBS->MUTATION_BLOCK_SIZE,
+			    std::min(value.size() - part * CLIENT_KNOBS->MUTATION_BLOCK_SIZE, CLIENT_KNOBS->MUTATION_BLOCK_SIZE));
+			Standalone<StringRef> key = getBlockKey(commitVersion, part);
+			wait(writeKV_impl(self, key, partBuf));
+		}
+		return Void();
+	}
+
+private:
+	Reference<IBackupFile> file;
+	int blockSize;
+	int64_t blockEnd = 0;
+};
+
+ACTOR Future<Void> convert(ConvertParams params) {
+	state Reference<IBackupContainer> container = IBackupContainer::openContainer(params.container_url);
+	state BackupFileList listing = wait(container->dumpFileList());
+	std::sort(listing.logs.begin(), listing.logs.end());
+	TraceEvent("Container").detail("URL", params.container_url).detail("Logs", listing.logs.size());
+	state BackupDescription desc = wait(container->describeBackup());
+	std::cout << "\n" << desc.toString() << "\n";
+
+	// std::cout << "Using Protocol Version: 0x" << std::hex << currentProtocolVersion.version() << std::dec << "\n";
+
+	std::vector<LogFile> logs = getRelevantLogFiles(listing.logs, params.begin, params.end);
+	printLogFiles("Range has", logs);
+
+	state Reference<MutationFilesReadProgress> progress(new MutationFilesReadProgress(logs, params.begin, params.end));
+
+	wait(progress->openLogFiles(container));
+
+	state int blockSize = CLIENT_KNOBS->BACKUP_LOGFILE_BLOCK_SIZE;
+	state Reference<IBackupFile> outFile = wait(container->writeLogFile(params.begin, params.end, blockSize));
+	state LogFileWriter logFile(outFile, blockSize);
+	std::cout << "Output file: " << outFile->getFileName() << "\n";
+
+	state MutationList list;
+	state Arena arena;
+	state Version version = invalidVersion;
+	while (progress->hasMutations()) {
+		state VersionedData data = wait(progress->getNextMutation());
+
+		// emit a mutation batch to file when encounter a new version
+		if (list.totalSize() > 0 && version != data.version.version) {
+			wait(LogFileWriter::addMutation(&logFile, version, list));
+			list = MutationList();
+			arena = Arena();
+		}
+
+		BinaryReader rd(data.message, AssumeVersion(currentProtocolVersion));
+		MutationRef m;
+		rd >> m;
+		std::cout << data.version.toString() << " m = " << m.toString() << "\n";
+		list.push_back_deep(arena, m);
+		version = data.version.version;
+	}
+	if (list.totalSize() > 0) {
+		wait(LogFileWriter::addMutation(&logFile, version, list));
+	}
+
+	wait(outFile->finish());
+
+	return Void();
+}
+
+int parseCommandLine(ConvertParams* param, CSimpleOpt* args) {
+	while (args->Next()) {
+		auto lastError = args->LastError();
+		switch (lastError) {
+		case SO_SUCCESS:
+			break;
+
+		default:
+			std::cerr << "ERROR: argument given for option: " << args->OptionText() << "\n";
+			return FDB_EXIT_ERROR;
+			break;
+		}
+
+		int optId = args->OptionId();
+		const char* arg = args->OptionArg();
+		switch (optId) {
+		case OPT_HELP:
+			printConvertUsage();
+			return FDB_EXIT_ERROR;
+
+		case OPT_BEGIN_VERSION:
+			if (!sscanf(arg, "%" SCNd64, &param->begin)) {
+				std::cerr << "ERROR: could not parse begin version " << arg << "\n";
+				printConvertUsage();
+				return FDB_EXIT_ERROR;
+			}
+			break;
+
+		case OPT_END_VERSION:
+			if (!sscanf(arg, "%" SCNd64, &param->end)) {
+				std::cerr << "ERROR: could not parse end version " << arg << "\n";
+				printConvertUsage();
+				return FDB_EXIT_ERROR;
+			}
+			break;
+
+		case OPT_CONTAINER:
+			param->container_url = args->OptionArg();
+			break;
+
+		case OPT_TRACE:
+			param->log_enabled = true;
+			break;
+
+		case OPT_TRACE_DIR:
+			param->log_dir = args->OptionArg();
+			break;
+
+		case OPT_TRACE_FORMAT:
+			if (!validateTraceFormat(args->OptionArg())) {
+				std::cerr << "ERROR: Unrecognized trace format " << args->OptionArg() << "\n";
+				return FDB_EXIT_ERROR;
+			}
+			param->trace_format = args->OptionArg();
+			break;
+
+		case OPT_TRACE_LOG_GROUP:
+			param->trace_log_group = args->OptionArg();
+			break;
+		}
+	}
+	return FDB_EXIT_SUCCESS;
+}
+
+}  // namespace file_converter
+
+int main(int argc, char** argv) {
+	try {
+		CSimpleOpt* args = new CSimpleOpt(argc, argv, file_converter::gConverterOptions, SO_O_EXACT);
+		file_converter::ConvertParams param;
+		int status = file_converter::parseCommandLine(&param, args);
+		std::cout << "Params: " << param.toString() << "\n";
+		if (status != FDB_EXIT_SUCCESS || !param.isValid()) {
+			file_converter::printConvertUsage();
+			return status;
+		}
+
+		if (param.log_enabled) {
+			if (param.log_dir.empty()) {
+				setNetworkOption(FDBNetworkOptions::TRACE_ENABLE);
+			} else {
+				setNetworkOption(FDBNetworkOptions::TRACE_ENABLE, StringRef(param.log_dir));
+			}
+			if (!param.trace_format.empty()) {
+				setNetworkOption(FDBNetworkOptions::TRACE_FORMAT, StringRef(param.trace_format));
+			}
+			if (!param.trace_log_group.empty()) {
+				setNetworkOption(FDBNetworkOptions::TRACE_LOG_GROUP, StringRef(param.trace_log_group));
+			}
+		}
+
+		platformInit();
+		Error::init();
+
+		StringRef url(param.container_url);
+		setupNetwork(0, true);
+
+		TraceEvent::setNetworkThread();
+		openTraceFile(NetworkAddress(), 10 << 20, 10 << 20, param.log_dir, "convert", param.trace_log_group);
+
+		auto f = stopAfter(convert(param));
+
+		runNetwork();
+		return status;
+	} catch (Error& e) {
+		fprintf(stderr, "ERROR: %s\n", e.what());
+		return FDB_EXIT_ERROR;
+	} catch (std::exception& e) {
+		TraceEvent(SevError, "MainError").error(unknown_error()).detail("RootException", e.what());
+		return FDB_EXIT_MAIN_EXCEPTION;
+	}
+}

fdbbackup/FileConverter.h

@@ -0,0 +1,65 @@
+/*
+ * FileConverter.h
+ *
+ * This source file is part of the FoundationDB open source project
+ *
+ * Copyright 2013-2019 Apple Inc. and the FoundationDB project authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef FDBBACKUP_FILECONVERTER_H
+#define FDBBACKUP_FILECONVERTER_H
+#pragma once
+
+#include <cinttypes>
+#include "flow/SimpleOpt.h"
+
+namespace file_converter {
+
+// File format convertion constants
+enum {
+	OPT_CONTAINER,
+	OPT_BEGIN_VERSION,
+	OPT_END_VERSION,
+	OPT_TRACE,
+	OPT_TRACE_DIR,
+	OPT_TRACE_FORMAT,
+	OPT_TRACE_LOG_GROUP,
+	OPT_INPUT_FILE,
+	OPT_HELP
+};
+
+CSimpleOpt::SOption gConverterOptions[] = { { OPT_CONTAINER, "-r", SO_REQ_SEP },
+	                                        { OPT_CONTAINER, "--container", SO_REQ_SEP },
+	                                        { OPT_BEGIN_VERSION, "-b", SO_REQ_SEP },
+	                                        { OPT_BEGIN_VERSION, "--begin", SO_REQ_SEP },
+	                                        { OPT_END_VERSION, "-e", SO_REQ_SEP },
+	                                        { OPT_END_VERSION, "--end", SO_REQ_SEP },
+	                                        { OPT_TRACE, "--log", SO_NONE },
+	                                        { OPT_TRACE_DIR, "--logdir", SO_REQ_SEP },
+	                                        { OPT_TRACE_FORMAT, "--trace_format", SO_REQ_SEP },
+	                                        { OPT_TRACE_LOG_GROUP, "--loggroup", SO_REQ_SEP },
+	                                        { OPT_INPUT_FILE, "-i", SO_REQ_SEP },
+	                                        { OPT_INPUT_FILE, "--input", SO_REQ_SEP },
+	                                        { OPT_HELP, "-?", SO_NONE },
+	                                        { OPT_HELP, "-h", SO_NONE },
+	                                        { OPT_HELP, "--help", SO_NONE },
+	                                        SO_END_OF_OPTIONS };
+
+}  // namespace file_converter
+
+// Mutation log version written by old FileBackupAgent
+static const uint32_t BACKUP_AGENT_MLOG_VERSION = 2001;
+
+#endif  // FDBBACKUP_FILECONVERTER_H

fdbbackup/FileDecoder.actor.cpp

@@ -0,0 +1,440 @@
+/*
+ * FileDecoder.actor.cpp
+ *
+ * This source file is part of the FoundationDB open source project
+ *
+ * Copyright 2013-2019 Apple Inc. and the FoundationDB project authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <algorithm>
+#include <iostream>
+#include <vector>
+
+#include "fdbclient/BackupAgent.actor.h"
+#include "fdbclient/BackupContainer.h"
+#include "fdbbackup/FileConverter.h"
+#include "fdbclient/MutationList.h"
+#include "flow/flow.h"
+#include "flow/serialize.h"
+
+namespace file_converter {
+
+void printDecodeUsage() {
+	std::cout << "\n"
+	             "  -r, --container   Container URL.\n"
+	             "  -i, --input FILE  Log file to be decoded.\n"
+	             "\n";
+	return;
+}
+
+struct DecodeParams {
+	std::string container_url;
+	std::string file;
+	bool log_enabled = false;
+	std::string log_dir, trace_format, trace_log_group;
+
+	std::string toString() {
+		std::string s;
+		s.append("ContainerURL: ");
+		s.append(container_url);
+		s.append(", File: ");
+		s.append(file);
+		if (log_enabled) {
+			if (!log_dir.empty()) {
+				s.append(" LogDir:").append(log_dir);
+			}
+			if (!trace_format.empty()) {
+				s.append(" Format:").append(trace_format);
+			}
+			if (!trace_log_group.empty()) {
+				s.append(" LogGroup:").append(trace_log_group);
+			}
+		}
+		return s;
+	}
+};
+
+int parseDecodeCommandLine(DecodeParams* param, CSimpleOpt* args) {
+	while (args->Next()) {
+		auto lastError = args->LastError();
+		switch (lastError) {
+		case SO_SUCCESS:
+			break;
+
+		default:
+			std::cerr << "ERROR: argument given for option: " << args->OptionText() << "\n";
+			return FDB_EXIT_ERROR;
+			break;
+		}
+		int optId = args->OptionId();
+		switch (optId) {
+		case OPT_HELP:
+			printDecodeUsage();
+			return FDB_EXIT_ERROR;
+
+		case OPT_CONTAINER:
+			param->container_url = args->OptionArg();
+			break;
+
+		case OPT_INPUT_FILE:
+			param->file = args->OptionArg();
+			break;
+
+		case OPT_TRACE:
+			param->log_enabled = true;
+			break;
+
+		case OPT_TRACE_DIR:
+			param->log_dir = args->OptionArg();
+			break;
+
+		case OPT_TRACE_FORMAT:
+			if (!validateTraceFormat(args->OptionArg())) {
+				std::cerr << "ERROR: Unrecognized trace format " << args->OptionArg() << "\n";
+				return FDB_EXIT_ERROR;
+			}
+			param->trace_format = args->OptionArg();
+			break;
+
+		case OPT_TRACE_LOG_GROUP:
+			param->trace_log_group = args->OptionArg();
+			break;
+		}
+	}
+	return FDB_EXIT_SUCCESS;
+}
+
+void printLogFiles(std::string msg, const std::vector<LogFile>& files) {
+	std::cout << msg << " " << files.size() << " log files\n";
+	for (const auto& file : files) {
+		std::cout << file.toString() << "\n";
+	}
+	std::cout << std::endl;
+}
+
+std::vector<LogFile> getRelevantLogFiles(const std::vector<LogFile>& files, const DecodeParams& params) {
+	std::vector<LogFile> filtered;
+	for (const auto& file : files) {
+		if (file.fileName.find(params.file) != std::string::npos) {
+			filtered.push_back(file);
+		}
+	}
+	return filtered;
+}
+
+std::pair<Version, int32_t> decode_key(const StringRef& key) {
+	ASSERT(key.size() == sizeof(uint8_t) + sizeof(Version) + sizeof(int32_t));
+
+	uint8_t hash;
+	Version version;
+	int32_t part;
+	BinaryReader rd(key, Unversioned());
+	rd >> hash >> version >> part;
+	version = bigEndian64(version);
+	part = bigEndian32(part);
+
+	int32_t v = version / CLIENT_KNOBS->LOG_RANGE_BLOCK_SIZE;
+	ASSERT(((uint8_t)hashlittle(&v, sizeof(v), 0)) == hash);
+
+	return std::make_pair(version, part);
+}
+
+// Decodes an encoded list of mutations in the format of:
+//   [includeVersion:uint64_t][val_length:uint32_t][mutation_1][mutation_2]...[mutation_k],
+// where a mutation is encoded as:
+//   [type:uint32_t][keyLength:uint32_t][valueLength:uint32_t][key][value]
+std::vector<MutationRef> decode_value(const StringRef& value) {
+	StringRefReader reader(value, restore_corrupted_data());
+
+	reader.consume<uint64_t>(); // Consume the includeVersion
+	uint32_t val_length = reader.consume<uint32_t>();
+	ASSERT(val_length == value.size() - sizeof(uint64_t) - sizeof(uint32_t));
+
+	std::vector<MutationRef> mutations;
+	while (1) {
+		if (reader.eof()) break;
+
+		// Deserialization of a MutationRef, which was packed by MutationListRef::push_back_deep()
+		uint32_t type, p1len, p2len;
+		type = reader.consume<uint32_t>();
+		p1len = reader.consume<uint32_t>();
+		p2len = reader.consume<uint32_t>();
+
+		const uint8_t* key = reader.consume(p1len);
+		const uint8_t* val = reader.consume(p2len);
+
+		mutations.emplace_back((MutationRef::Type)type, StringRef(key, p1len), StringRef(val, p2len));
+	}
+	return mutations;
+}
+
+struct VersionedMutations {
+	Version version;
+	std::vector<MutationRef> mutations;
+	Arena arena; // The arena that contains the mutations.
+};
+
+/*
+ * Model a decoding progress for a mutation file. Usage is:
+ *
+ *    DecodeProgress progress(logfile);
+ *    wait(progress->openFile(container));
+ *    while (!progress->finished()) {
+ *        VersionedMutations m = wait(progress->getNextBatch());
+ *        ...
+ *    }
+ *
+ * Internally, the decoding process is done block by block -- each block is
+ * decoded into a list of key/value pairs, which are then decoded into batches
+ * of mutations. Because a version's mutations can be split into many key/value
+ * pairs, the decoding of mutation batch needs to look ahead one more pair. So
+ * at any time this object might have two blocks of data in memory.
+ */
+struct DecodeProgress {
+	DecodeProgress() = default;
+	DecodeProgress(const LogFile& file) : file(file) {}
+
+	// If there are no more mutations to pull.
+	bool finished() { return eof && keyValues.empty(); }
+
+	// Returns all mutations of the next version in a batch.
+	Future<VersionedMutations> getNextBatch() { return getNextBatchImpl(this); }
+
+	Future<Void> openFile(Reference<IBackupContainer> container) { return openFileImpl(this, container); }
+
+	// The following are private APIs:
+
+	// PRECONDITION: finished() must return false before calling this function.
+	// Returns the next batch of mutations along with the arena backing it.
+	ACTOR static Future<VersionedMutations> getNextBatchImpl(DecodeProgress* self) {
+		ASSERT(!self->finished());
+
+		state std::pair<Arena, KeyValueRef> arena_kv = self->keyValues[0];
+
+		// decode this batch's version
+		state std::pair<Version, int32_t> version_part = decode_key(arena_kv.second.key);
+		ASSERT(version_part.second == 0); // first part number must be 0.
+
+		// decode next versions, check if they are continuous parts
+		state int idx = 1; // next kv pair in "keyValues"
+		state int bufSize = arena_kv.second.value.size();
+		state int lastPart = 0;
+		loop {
+			// Try to decode another block if needed
+			if (idx == self->keyValues.size()) {
+				wait(readAndDecodeFile(self));
+			}
+			if (idx == self->keyValues.size()) break;
+
+			std::pair<Version, int32_t> next_version_part = decode_key(self->keyValues[idx].second.key);
+			if (version_part.first != next_version_part.first) break;
+
+			if (lastPart + 1 != next_version_part.second) {
+				TraceEvent("DecodeError").detail("Part1", lastPart).detail("Part2", next_version_part.second);
+				throw restore_corrupted_data();
+			}
+			bufSize += self->keyValues[idx].second.value.size();
+			idx++;
+			lastPart++;
+		}
+
+		VersionedMutations m;
+		m.version = version_part.first;
+		if (idx > 1) {
+			// Stitch parts into one and then decode one by one
+			Standalone<StringRef> buf = self->combineValues(idx, bufSize);
+			m.mutations = decode_value(buf);
+			m.arena = buf.arena();
+		} else {
+			m.mutations = decode_value(arena_kv.second.value);
+			m.arena = arena_kv.first;
+		}
+		self->keyValues.erase(self->keyValues.begin(), self->keyValues.begin() + idx);
+
+		return m;
+	}
+
+	// Returns a buffer which stitches first "idx" values into one.
+	// "len" MUST equal the summation of these values.
+	Standalone<StringRef> combineValues(const int idx, const int len) {
+		ASSERT(idx <= keyValues.size() && idx > 1);
+
+		Standalone<StringRef> buf = makeString(len);
+		int n = 0;
+		for (int i = 0; i < idx; i++) {
+			const auto& value = keyValues[i].second.value;
+			memcpy(mutateString(buf) + n, value.begin(), value.size());
+			n += value.size();
+		}
+
+		ASSERT(n == len);
+		return buf;
+	}
+
+	// Decodes a block into KeyValueRef stored in "keyValues".
+	void decode_block(const Standalone<StringRef>& buf, int len) {
+		StringRef block(buf.begin(), len);
+		StringRefReader reader(block, restore_corrupted_data());
+
+		try {
+			// Read header, currently only decoding version 2001
+			if (reader.consume<int32_t>() != BACKUP_AGENT_MLOG_VERSION) throw restore_unsupported_file_version();
+
+			// Read k/v pairs. Block ends either at end of last value exactly or with 0xFF as first key len byte.
+			while (1) {
+				// If eof reached or first key len bytes is 0xFF then end of block was reached.
+				if (reader.eof() || *reader.rptr == 0xFF) break;
+
+				// Read key and value.  If anything throws then there is a problem.
+				uint32_t kLen = reader.consumeNetworkUInt32();
+				const uint8_t* k = reader.consume(kLen);
+				uint32_t vLen = reader.consumeNetworkUInt32();
+				const uint8_t* v = reader.consume(vLen);
+				keyValues.emplace_back(buf.arena(), KeyValueRef(StringRef(k, kLen), StringRef(v, vLen)));
+			}
+
+			// Make sure any remaining bytes in the block are 0xFF
+			for (auto b : reader.remainder()) {
+				if (b != 0xFF) throw restore_corrupted_data_padding();
+			}
+
+			return;
+		} catch (Error& e) {
+			TraceEvent(SevWarn, "CorruptBlock").error(e).detail("Offset", reader.rptr - buf.begin());
+			throw;
+		}
+	}
+
+	ACTOR static Future<Void> openFileImpl(DecodeProgress* self, Reference<IBackupContainer> container) {
+		Reference<IAsyncFile> fd = wait(container->readFile(self->file.fileName));
+		self->fd = fd;
+		wait(readAndDecodeFile(self));
+		return Void();
+	}
+
+	// Reads a file block, decodes it into key/value pairs, and stores these pairs.
+	ACTOR static Future<Void> readAndDecodeFile(DecodeProgress* self) {
+		try {
+			state int64_t len = std::min<int64_t>(self->file.blockSize, self->file.fileSize - self->offset);
+			if (len == 0) {
+				self->eof = true;
+				return Void();
+			}
+
+			state Standalone<StringRef> buf = makeString(len);
+			state int rLen = wait(self->fd->read(mutateString(buf), len, self->offset));
+			TraceEvent("ReadFile")
+			    .detail("Name", self->file.fileName)
+			    .detail("Len", rLen)
+			    .detail("Offset", self->offset);
+			if (rLen != len) {
+				throw restore_corrupted_data();
+			}
+			self->decode_block(buf, rLen);
+			self->offset += rLen;
+			return Void();
+		} catch (Error& e) {
+			TraceEvent(SevWarn, "CorruptLogFileBlock")
+			    .error(e)
+			    .detail("Filename", self->file.fileName)
+			    .detail("BlockOffset", self->offset)
+			    .detail("BlockLen", self->file.blockSize);
+			throw;
+		}
+	}
+
+	LogFile file;
+	Reference<IAsyncFile> fd;
+	int64_t offset = 0;
+	bool eof = false;
+	// Key value pairs and their memory arenas.
+	std::vector<std::pair<Arena, KeyValueRef>> keyValues;
+};
+
+ACTOR Future<Void> decode_logs(DecodeParams params) {
+	state Reference<IBackupContainer> container = IBackupContainer::openContainer(params.container_url);
+
+	state BackupFileList listing = wait(container->dumpFileList());
+	std::sort(listing.logs.begin(), listing.logs.end());
+	TraceEvent("Container").detail("URL", params.container_url).detail("Logs", listing.logs.size());
+
+	BackupDescription desc = wait(container->describeBackup());
+	std::cout << "\n" << desc.toString() << "\n";
+
+	state std::vector<LogFile> logs = getRelevantLogFiles(listing.logs, params);
+	printLogFiles("Relevant files are: ", logs);
+
+	state int i = 0;
+	for (; i < logs.size(); i++) {
+		state DecodeProgress progress(logs[i]);
+		wait(progress.openFile(container));
+		while (!progress.finished()) {
+			VersionedMutations vms = wait(progress.getNextBatch());
+			for (const auto& m : vms.mutations) {
+				std::cout << vms.version << " " << m.toString() << "\n";
+			}
+		}
+	}
+	return Void();
+}
+
+} // namespace file_converter
+
+int main(int argc, char** argv) {
+	try {
+		CSimpleOpt* args = new CSimpleOpt(argc, argv, file_converter::gConverterOptions, SO_O_EXACT);
+		file_converter::DecodeParams param;
+		int status = file_converter::parseDecodeCommandLine(&param, args);
+		std::cout << "Params: " << param.toString() << "\n";
+		if (status != FDB_EXIT_SUCCESS) {
+			file_converter::printDecodeUsage();
+			return status;
+		}
+
+		if (param.log_enabled) {
+			if (param.log_dir.empty()) {
+				setNetworkOption(FDBNetworkOptions::TRACE_ENABLE);
+			} else {
+				setNetworkOption(FDBNetworkOptions::TRACE_ENABLE, StringRef(param.log_dir));
+			}
+			if (!param.trace_format.empty()) {
+				setNetworkOption(FDBNetworkOptions::TRACE_FORMAT, StringRef(param.trace_format));
+			}
+			if (!param.trace_log_group.empty()) {
+				setNetworkOption(FDBNetworkOptions::TRACE_LOG_GROUP, StringRef(param.trace_log_group));
+			}
+		}
+
+		platformInit();
+		Error::init();
+
+		StringRef url(param.container_url);
+		setupNetwork(0, true);
+
+		TraceEvent::setNetworkThread();
+		openTraceFile(NetworkAddress(), 10 << 20, 10 << 20, param.log_dir, "decode", param.trace_log_group);
+
+		auto f = stopAfter(decode_logs(param));
+
+		runNetwork();
+		return status;
+	} catch (Error& e) {
+		fprintf(stderr, "ERROR: %s\n", e.what());
+		return FDB_EXIT_ERROR;
+	} catch (std::exception& e) {
+		TraceEvent(SevError, "MainError").error(unknown_error()).detail("RootException", e.what());
+		return FDB_EXIT_MAIN_EXCEPTION;
+	}
+}

fdbclient/BackupAgent.actor.h

@@ -487,7 +487,7 @@ Standalone<VectorRef<KeyRangeRef>> getLogRanges(Version beginVersion, Version en
 Standalone<VectorRef<KeyRangeRef>> getApplyRanges(Version beginVersion, Version endVersion, Key backupUid);
 Future<Void> eraseLogData(Reference<ReadYourWritesTransaction> tr, Key logUidValue, Key destUidValue, Optional<Version> endVersion = Optional<Version>(), bool checkBackupUid = false, Version backupUid = 0);
 Key getApplyKey( Version version, Key backupUid );
-std::pair<uint64_t, uint32_t> decodeBKMutationLogKey(Key key);
+std::pair<Version, uint32_t> decodeBKMutationLogKey(Key key);
 Standalone<VectorRef<MutationRef>> decodeBackupLogValue(StringRef value);
 void decodeBackupLogValue(Arena& arena, VectorRef<MutationRef>& result, int64_t& mutationSize, StringRef value, StringRef addPrefix = StringRef(), StringRef removePrefix = StringRef());
 Future<Void> logError(Database cx, Key keyErrors, const std::string& message);
@@ -848,5 +848,38 @@ ACTOR Future<Version> fastRestore(Database cx, Standalone<StringRef> tagName, St
                                   bool waitForComplete, long targetVersion, bool verbose, Standalone<KeyRangeRef> range,
                                   Standalone<StringRef> addPrefix, Standalone<StringRef> removePrefix);
 
+// Helper class for reading restore data from a buffer and throwing the right errors.
+struct StringRefReader {
+	StringRefReader(StringRef s = StringRef(), Error e = Error()) : rptr(s.begin()), end(s.end()), failure_error(e) {}
+
+	// Return remainder of data as a StringRef
+	StringRef remainder() { return StringRef(rptr, end - rptr); }
+
+	// Return a pointer to len bytes at the current read position and advance read pos
+	const uint8_t* consume(unsigned int len) {
+		if (rptr == end && len != 0) throw end_of_stream();
+		const uint8_t* p = rptr;
+		rptr += len;
+		if (rptr > end) throw failure_error;
+		return p;
+	}
+
+	// Return a T from the current read position and advance read pos
+	template <typename T>
+	const T consume() {
+		return *(const T*)consume(sizeof(T));
+	}
+
+	// Functions for consuming big endian (network byte order) integers.
+	// Consumes a big endian number, swaps it to little endian, and returns it.
+	const int32_t consumeNetworkInt32() { return (int32_t)bigEndian32((uint32_t)consume<int32_t>()); }
+	const uint32_t consumeNetworkUInt32() { return bigEndian32(consume<uint32_t>()); }
+
+	bool eof() { return rptr == end; }
+
+	const uint8_t *rptr, *end;
+	Error failure_error;
+};
+
 #include "flow/unactorcompiler.h"
 #endif

fdbclient/BackupAgentBase.actor.cpp

@@ -131,7 +131,7 @@ bool copyParameter(Reference<Task> source, Reference<Task> dest, Key key) {
 }
 
 Version getVersionFromString(std::string const& value) {
-	Version version(-1);
+	Version version = invalidVersion;
 	int n = 0;
 	if (sscanf(value.c_str(), "%lld%n", (long long*)&version, &n) != 1 || n != value.size()) {
 		TraceEvent(SevWarnAlways, "GetVersionFromString").detail("InvalidVersion", value);
@@ -204,7 +204,7 @@ Key getApplyKey( Version version, Key backupUid ) {
 //returns(version, part) where version is the database version number of
 //the transaction log data in the value, and part is 0 for the first such
 //data for a given version, 1 for the second block of data, etc.
-std::pair<uint64_t, uint32_t> decodeBKMutationLogKey(Key key) {
+std::pair<Version, uint32_t> decodeBKMutationLogKey(Key key) {
 	return std::make_pair(bigEndian64(*(int64_t*)(key.begin() + backupLogPrefixBytes + sizeof(UID) + sizeof(uint8_t))),
 		bigEndian32(*(int32_t*)(key.begin() + backupLogPrefixBytes + sizeof(UID) + sizeof(uint8_t) + sizeof(int64_t))));
 }
@@ -379,7 +379,9 @@ void decodeBackupLogValue(Arena& arena, VectorRef<MutationRef>& result, int& mut
 		throw;
 	}
 }
+
 static double lastErrorTime = 0;
+
 void logErrorWorker(Reference<ReadYourWritesTransaction> tr, Key keyErrors, std::string message) {
 	tr->setOption(FDBTransactionOptions::ACCESS_SYSTEM_KEYS);
 	tr->setOption(FDBTransactionOptions::LOCK_AWARE);

fdbclient/BackupContainer.actor.cpp

@@ -39,7 +39,7 @@
 
 namespace IBackupFile_impl {
 
-	ACTOR Future<Void> appendStringRefWithLen(Reference<IBackupFile> file, Standalone<StringRef> s) {
+ACTOR Future<Void> appendStringRefWithLen(Reference<IBackupFile> file, Standalone<StringRef> s) {
 		state uint32_t lenBuf = bigEndian32((uint32_t)s.size());
 		wait(file->append(&lenBuf, sizeof(lenBuf)));
 		wait(file->append(s.begin(), s.size()));
@@ -258,15 +258,15 @@ std::string BackupDescription::toJSON() const {
  */
 class BackupContainerFileSystem : public IBackupContainer {
 public:
-	virtual void addref() = 0;
-	virtual void delref() = 0;
+	void addref() override = 0;
+	void delref() override = 0;
 
 	BackupContainerFileSystem() {}
 	virtual ~BackupContainerFileSystem() {}
 
 	// Create the container
-	virtual Future<Void> create() = 0;
-	virtual Future<bool> exists() = 0;
+	Future<Void> create() override = 0;
+	Future<bool> exists() override = 0;
 
 	// Get a list of fileNames and their sizes in the container under the given path
 	// Although not required, an implementation can avoid traversing unwanted subfolders
@@ -275,7 +275,7 @@ public:
 	virtual Future<FilesAndSizesT> listFiles(std::string path = "", std::function<bool(std::string const &)> folderPathFilter = nullptr) = 0;
 
 	// Open a file for read by fileName
-	virtual Future<Reference<IAsyncFile>> readFile(std::string fileName) = 0;
+	Future<Reference<IAsyncFile>> readFile(std::string fileName) override = 0;
 
 	// Open a file for write by fileName
 	virtual Future<Reference<IBackupFile>> writeFile(std::string fileName) = 0;
@@ -285,7 +285,7 @@ public:
 
 	// Delete entire container.  During the process, if pNumDeleted is not null it will be
 	// updated with the count of deleted files so that progress can be seen.
-	virtual Future<Void> deleteContainer(int *pNumDeleted) = 0;
+	Future<Void> deleteContainer(int* pNumDeleted) override = 0;
 
 	// Creates a 2-level path (x/y) where v should go such that x/y/* contains (10^smallestBucket) possible versions
 	static std::string versionFolderString(Version v, int smallestBucket) {
@@ -333,11 +333,18 @@ public:
 		return format("logs/%s/", versionFolderString(v, 11).c_str());
 	}
 
-	Future<Reference<IBackupFile>> writeLogFile(Version beginVersion, Version endVersion, int blockSize) {
+	Future<Reference<IBackupFile>> writeLogFile(Version beginVersion, Version endVersion, int blockSize) override {
 		return writeFile(logVersionFolderString(beginVersion) + format("log,%lld,%lld,%s,%d", beginVersion, endVersion, deterministicRandom()->randomUniqueID().toString().c_str(), blockSize));
 	}
 
-	Future<Reference<IBackupFile>> writeRangeFile(Version snapshotBeginVersion, int snapshotFileCount, Version fileVersion, int blockSize) {
+	Future<Reference<IBackupFile>> writeTaggedLogFile(Version beginVersion, Version endVersion, int blockSize,
+	                                                  uint16_t tagId) override {
+		return writeFile(logVersionFolderString(beginVersion) +
+		                 format("log,%lld,%lld,%s,%d,%d", beginVersion, endVersion,
+		                        deterministicRandom()->randomUniqueID().toString().c_str(), blockSize, tagId));
+	}
+
+	Future<Reference<IBackupFile>> writeRangeFile(Version snapshotBeginVersion, int snapshotFileCount, Version fileVersion, int blockSize) override {
 		std::string fileName = format("range,%" PRId64 ",%s,%d", fileVersion, deterministicRandom()->randomUniqueID().toString().c_str(), blockSize);
 
 		// In order to test backward compatibility in simulation, sometimes write to the old path format
@@ -370,6 +377,11 @@ public:
 		if(sscanf(name.c_str(), "log,%" SCNd64 ",%" SCNd64 ",%*[^,],%u%n", &f.beginVersion, &f.endVersion, &f.blockSize, &len) == 3 && len == name.size()) {
 			out = f;
 			return true;
+		} else if (sscanf(name.c_str(), "log,%" SCNd64 ",%" SCNd64 ",%*[^,],%u,%d%n", &f.beginVersion, &f.endVersion,
+		                  &f.blockSize, &f.tagId, &len) == 4 &&
+		           len == name.size() && f.tagId >= 0) {
+			out = f;
+			return true;
 		}
 		return false;
 	}
@@ -495,7 +507,7 @@ public:
 		return Void();
 	}
 
-	Future<Void> writeKeyspaceSnapshotFile(std::vector<std::string> fileNames, int64_t totalBytes) {
+	Future<Void> writeKeyspaceSnapshotFile(std::vector<std::string> fileNames, int64_t totalBytes) override {
 		return writeKeyspaceSnapshotFile_impl(Reference<BackupContainerFileSystem>::addRef(this), fileNames, totalBytes);
 	};
 
@@ -612,7 +624,7 @@ public:
 		return BackupFileList({fRanges.get(), fLogs.get(), fSnapshots.get()});
 	}
 
-	Future<BackupFileList> dumpFileList(Version begin, Version end) {
+	Future<BackupFileList> dumpFileList(Version begin, Version end) override {
 		return dumpFileList_impl(Reference<BackupContainerFileSystem>::addRef(this), begin, end);
 	}
 
@@ -829,7 +841,7 @@ public:
 	}
 
 	// Uses the virtual methods to describe the backup contents
-	Future<BackupDescription> describeBackup(bool deepScan, Version logStartVersionOverride) {
+	Future<BackupDescription> describeBackup(bool deepScan, Version logStartVersionOverride) override {
 		return describeBackup_impl(Reference<BackupContainerFileSystem>::addRef(this), deepScan, logStartVersionOverride);
 	}
 
@@ -1009,7 +1021,7 @@ public:
 	}
 
 	// Delete all data up to (but not including endVersion)
-	Future<Void> expireData(Version expireEndVersion, bool force, ExpireProgress *progress, Version restorableBeginVersion) {
+	Future<Void> expireData(Version expireEndVersion, bool force, ExpireProgress *progress, Version restorableBeginVersion) override {
 		return expireData_impl(Reference<BackupContainerFileSystem>::addRef(this), expireEndVersion, force, progress, restorableBeginVersion);
 	}
 
@@ -1067,7 +1079,7 @@ public:
 		return Optional<RestorableFileSet>();
 	}
 
-	Future<Optional<RestorableFileSet>> getRestoreSet(Version targetVersion){
+	Future<Optional<RestorableFileSet>> getRestoreSet(Version targetVersion) override {
 		return getRestoreSet_impl(Reference<BackupContainerFileSystem>::addRef(this), targetVersion);
 	}
 
@@ -1152,8 +1164,8 @@ public:
 
 class BackupContainerLocalDirectory : public BackupContainerFileSystem, ReferenceCounted<BackupContainerLocalDirectory> {
 public:
-	void addref() { return ReferenceCounted<BackupContainerLocalDirectory>::addref(); }
-	void delref() { return ReferenceCounted<BackupContainerLocalDirectory>::delref(); }
+	void addref() override { return ReferenceCounted<BackupContainerLocalDirectory>::addref(); }
+	void delref() override { return ReferenceCounted<BackupContainerLocalDirectory>::delref(); }
 
 	static std::string getURLFormat() { return "file://</path/to/base/dir/>"; }
 
@@ -1202,7 +1214,7 @@ public:
 		return results;
 	}
 
-	Future<Void> create() {
+	Future<Void> create() override {
 		// Nothing should be done here because create() can be called by any process working with the container URL, such as fdbbackup.
 		// Since "local directory" containers are by definition local to the machine they are accessed from,
 		// the container's creation (in this case the creation of a directory) must be ensured prior to every file creation,
@@ -1212,11 +1224,11 @@ public:
 	}
 
 	// The container exists if the folder it resides in exists
-	Future<bool> exists() {
+	Future<bool> exists() override {
 		return directoryExists(m_path);
 	}
 
-	Future<Reference<IAsyncFile>> readFile(std::string path) {
+	Future<Reference<IAsyncFile>> readFile(std::string path) override {
 		int flags = IAsyncFile::OPEN_NO_AIO | IAsyncFile::OPEN_READONLY | IAsyncFile::OPEN_UNCACHED;
 		// Simulation does not properly handle opening the same file from multiple machines using a shared filesystem,
 		// so create a symbolic link to make each file opening appear to be unique.  This could also work in production
@@ -1285,15 +1297,15 @@ public:
 			return finish_impl(Reference<BackupFile>::addRef(this));
 		}
 
-		void addref() { return ReferenceCounted<BackupFile>::addref(); }
-		void delref() { return ReferenceCounted<BackupFile>::delref(); }
+		void addref() override { return ReferenceCounted<BackupFile>::addref(); }
+		void delref() override { return ReferenceCounted<BackupFile>::delref(); }
 
 	private:
 		Reference<IAsyncFile> m_file;
 		std::string m_finalFullPath;
 	};
 
-	Future<Reference<IBackupFile>> writeFile(std::string path) {
+	Future<Reference<IBackupFile>> writeFile(std::string path) override {
 		int flags = IAsyncFile::OPEN_NO_AIO | IAsyncFile::OPEN_CREATE | IAsyncFile::OPEN_ATOMIC_WRITE_AND_CREATE | IAsyncFile::OPEN_READWRITE;
 		std::string fullPath = joinPath(m_path, path);
 		platform::createDirectory(parentDirectory(fullPath));
@@ -1304,7 +1316,7 @@ public:
 		});
 	}
 
-	Future<Void> deleteFile(std::string path) {
+	Future<Void> deleteFile(std::string path) override {
 		::deleteFile(joinPath(m_path, path));
 		return Void();
 	}
@@ -1329,7 +1341,7 @@ public:
 		return results;
 	}
 
-	Future<Void> deleteContainer(int *pNumDeleted) {
+	Future<Void> deleteContainer(int* pNumDeleted) override {
 		// In order to avoid deleting some random directory due to user error, first describe the backup
 		// and make sure it has something in it.
 		return map(describeBackup(false, invalidVersion), [=](BackupDescription const &desc) {
@@ -1389,8 +1401,8 @@ public:
 		}
 	}
 
-	void addref() { return ReferenceCounted<BackupContainerBlobStore>::addref(); }
-	void delref() { return ReferenceCounted<BackupContainerBlobStore>::delref(); }
+	void addref() override { return ReferenceCounted<BackupContainerBlobStore>::addref(); }
+	void delref() override { return ReferenceCounted<BackupContainerBlobStore>::delref(); }
 
 	static std::string getURLFormat() {
 		return BlobStoreEndpoint::getURLFormat(true) + " (Note: The 'bucket' parameter is required.)";
@@ -1398,7 +1410,7 @@ public:
 
 	virtual ~BackupContainerBlobStore() {}
 
-	Future<Reference<IAsyncFile>> readFile(std::string path) {
+	Future<Reference<IAsyncFile>> readFile(std::string path) override {
 			return Reference<IAsyncFile>(
 				new AsyncFileReadAheadCache(
 					Reference<IAsyncFile>(new AsyncFileBlobStoreRead(m_bstore, m_bucket, dataPath(path))),
@@ -1435,17 +1447,17 @@ public:
 			return map(m_file->sync(), [=](Void _) { self->m_file.clear(); return Void(); });
 		}
 
-		void addref() { return ReferenceCounted<BackupFile>::addref(); }
-		void delref() { return ReferenceCounted<BackupFile>::delref(); }
+		void addref() override { return ReferenceCounted<BackupFile>::addref(); }
+		void delref() override { return ReferenceCounted<BackupFile>::delref(); }
 	private:
 		Reference<IAsyncFile> m_file;
 	};
 
-	Future<Reference<IBackupFile>> writeFile(std::string path) {
+	Future<Reference<IBackupFile>> writeFile(std::string path) override {
 		return Reference<IBackupFile>(new BackupFile(path, Reference<IAsyncFile>(new AsyncFileBlobStoreWrite(m_bstore, m_bucket, dataPath(path)))));
 	}
 
-	Future<Void> deleteFile(std::string path) {
+	Future<Void> deleteFile(std::string path) override {
 		return m_bstore->deleteObject(m_bucket, dataPath(path));
 	}
 
@@ -1483,12 +1495,12 @@ public:
 		return Void();
 	}
 
-	Future<Void> create() {
+	Future<Void> create() override {
 		return create_impl(Reference<BackupContainerBlobStore>::addRef(this));
 	}
 
 	// The container exists if the index entry in the blob bucket exists
-	Future<bool> exists() {
+	Future<bool> exists() override {
 		return m_bstore->objectExists(m_bucket, indexEntry());
 	}
 
@@ -1508,7 +1520,7 @@ public:
 		return Void();
 	}
 
-	Future<Void> deleteContainer(int *pNumDeleted) {
+	Future<Void> deleteContainer(int* pNumDeleted) override {
 		return deleteContainer_impl(Reference<BackupContainerBlobStore>::addRef(this), pNumDeleted);
 	}
 

fdbclient/BackupContainer.h

@@ -68,17 +68,24 @@ struct LogFile {
 	uint32_t blockSize;
 	std::string fileName;
 	int64_t fileSize;
+	int tagId = -1; // Log router tag. Non-negative for new backup format.
 
 	// Order by beginVersion, break ties with endVersion
 	bool operator< (const LogFile &rhs) const {
 		return beginVersion == rhs.beginVersion ? endVersion < rhs.endVersion : beginVersion < rhs.beginVersion;
 	}
 
+	// Returns if two log files have the same content by comparing version range and tag ID.
+	bool sameContent(const LogFile& rhs) const {
+		return beginVersion == rhs.beginVersion && endVersion == rhs.endVersion && tagId == rhs.tagId;
+	}
+
 	std::string toString() const {
 		std::stringstream ss;
-		ss << "beginVersion:" << std::to_string(beginVersion) << " endVersion:" << std::to_string(endVersion) <<
-		      " blockSize:" << std::to_string(blockSize) << " filename:" << fileName <<
-		      " fileSize:" << std::to_string(fileSize);
+		ss << "beginVersion:" << std::to_string(beginVersion) << " endVersion:" << std::to_string(endVersion)
+		   << " blockSize:" << std::to_string(blockSize) << " filename:" << fileName
+		   << " fileSize:" << std::to_string(fileSize)
+		   << " tagId: " << (tagId >= 0 ? std::to_string(tagId) : std::string("(None)"));
 		return ss.str();
 	}
 };
@@ -205,6 +212,10 @@ public:
 	virtual Future<Reference<IBackupFile>> writeLogFile(Version beginVersion, Version endVersion, int blockSize) = 0;
 	virtual Future<Reference<IBackupFile>> writeRangeFile(Version snapshotBeginVersion, int snapshotFileCount, Version fileVersion, int blockSize) = 0;
 
+	// Open a tagged log file for writing, where tagId is the log router tag's id.
+	virtual Future<Reference<IBackupFile>> writeTaggedLogFile(Version beginVersion, Version endVersion, int blockSize,
+	                                                          uint16_t tagId) = 0;
+
 	// Write a KeyspaceSnapshotFile of range file names representing a full non overlapping
 	// snapshot of the key ranges this backup is targeting.
 	virtual Future<Void> writeKeyspaceSnapshotFile(std::vector<std::string> fileNames, int64_t totalBytes) = 0;

fdbclient/FDBTypes.h

@@ -42,11 +42,16 @@ enum {
 	tagLocalityRemoteLog = -3,
 	tagLocalityUpgraded = -4,
 	tagLocalitySatellite = -5,
-	tagLocalityLogRouterMapped = -6,
+	tagLocalityLogRouterMapped = -6,  // used by log router to pop from TLogs
 	tagLocalityTxs = -7,
+	tagLocalityBackup = -8,  // used by backup role to pop from TLogs
 	tagLocalityInvalid = -99
 }; //The TLog and LogRouter require these number to be as compact as possible
 
+inline bool isPseudoLocality(int8_t locality) {
+	return locality == tagLocalityLogRouterMapped || locality == tagLocalityBackup;
+}
+
 #pragma pack(push, 1)
 struct Tag {
 	int8_t locality;
@@ -966,4 +971,18 @@ struct HealthMetrics {
 	}
 };
 
+struct WorkerBackupStatus {
+	LogEpoch epoch;
+	Version version;
+	Tag tag;
+
+	WorkerBackupStatus() : epoch(0), version(invalidVersion) {}
+	WorkerBackupStatus(LogEpoch e, Version v, Tag t) : epoch(e), version(v), tag(t) {}
+
+	template <class Ar>
+	void serialize(Ar& ar) {
+		serializer(ar, epoch, version, tag);
+	}
+};
+
 #endif

fdbclient/FileBackupAgent.actor.cpp

@@ -545,42 +545,6 @@ namespace fileBackup {
 		Key lastValue;
 	};
 
-	// Helper class for reading restore data from a buffer and throwing the right errors.
-	struct StringRefReader {
-		StringRefReader(StringRef s = StringRef(), Error e = Error()) : rptr(s.begin()), end(s.end()), failure_error(e) {}
-
-		// Return remainder of data as a StringRef
-		StringRef remainder() {
-			return StringRef(rptr, end - rptr);
-		}
-
-		// Return a pointer to len bytes at the current read position and advance read pos
-		const uint8_t * consume(unsigned int len) {
-			if(rptr == end && len != 0)
-				throw end_of_stream();
-			const uint8_t *p = rptr;
-			rptr += len;
-			if(rptr > end)
-				throw failure_error;
-			return p;
-		}
-
-		// Return a T from the current read position and advance read pos
-		template<typename T> const T consume() {
-			return *(const T *)consume(sizeof(T));
-		}
-
-		// Functions for consuming big endian (network byte order) integers.
-		// Consumes a big endian number, swaps it to little endian, and returns it.
-		int32_t  consumeNetworkInt32()  { return (int32_t)bigEndian32((uint32_t)consume< int32_t>());}
-		uint32_t consumeNetworkUInt32() { return          bigEndian32(          consume<uint32_t>());}
-
-		bool eof() { return rptr == end; }
-
-		const uint8_t *rptr, *end;
-		Error failure_error;
-	};
-
 	ACTOR Future<Standalone<VectorRef<KeyValueRef>>> decodeRangeFileBlock(Reference<IAsyncFile> file, int64_t offset, int len) {
 		state Standalone<StringRef> buf = makeString(len);
 		int rLen = wait(file->read(mutateString(buf), len, offset));

fdbclient/MasterProxyInterface.h

@@ -173,6 +173,7 @@ struct GetReadVersionRequest : TimedRequest {
 		PRIORITY_BATCH = 1 << 24
 	};
 	enum {
+		FLAG_USE_MIN_KNOWN_COMMITTED_VERSION = 4,
 		FLAG_USE_PROVISIONAL_PROXIES = 2,
 		FLAG_CAUSAL_READ_RISKY = 1,
 		FLAG_PRIORITY_MASK = PRIORITY_SYSTEM_IMMEDIATE,

fdbclient/SystemData.cpp

@@ -491,6 +491,38 @@ ProcessData decodeWorkerListValue( ValueRef const& value ) {
 	return s;
 }
 
+const KeyRangeRef backupProgressKeys(LiteralStringRef("\xff\x02/backupProgress/"),
+                                     LiteralStringRef("\xff\x02/backupProgress0"));
+const KeyRef backupProgressPrefix = backupProgressKeys.begin;
+const KeyRef backupStartedKey = LiteralStringRef("\xff\x02/backupStarted");
+
+const Key backupProgressKeyFor(UID workerID) {
+	BinaryWriter wr(Unversioned());
+	wr.serializeBytes(backupProgressPrefix);
+	wr << workerID;
+	return wr.toValue();
+}
+
+const Value backupProgressValue(const WorkerBackupStatus& status) {
+	BinaryWriter wr(IncludeVersion());
+	wr << status;
+	return wr.toValue();
+}
+
+UID decodeBackupProgressKey(const KeyRef& key) {
+	UID serverID;
+	BinaryReader rd(key.removePrefix(backupProgressPrefix), Unversioned());
+	rd >> serverID;
+	return serverID;
+}
+
+WorkerBackupStatus decodeBackupProgressValue(const ValueRef& value) {
+	WorkerBackupStatus status;
+	BinaryReader reader(value, IncludeVersion());
+	reader >> status;
+	return status;
+}
+
 const KeyRef coordinatorsKey = LiteralStringRef("\xff/coordinators");
 const KeyRef logsKey = LiteralStringRef("\xff/logs");
 const KeyRef minRequiredCommitVersionKey = LiteralStringRef("\xff/minRequiredCommitVersion");

fdbclient/SystemData.h

@@ -174,6 +174,17 @@ const Value workerListValue( ProcessData const& );
 Key decodeWorkerListKey( KeyRef const& );
 ProcessData decodeWorkerListValue( ValueRef const& );
 
+//    "\xff/backupProgress/[[workerID]]" := "[[WorkerBackupStatus]]"
+extern const KeyRangeRef backupProgressKeys;
+extern const KeyRef backupProgressPrefix;
+const Key backupProgressKeyFor(UID workerID);
+const Value backupProgressValue(const WorkerBackupStatus& status);
+UID decodeBackupProgressKey(const KeyRef& key);
+WorkerBackupStatus decodeBackupProgressValue(const ValueRef& value);
+
+//    "\xff/backupStarted"
+extern const KeyRef backupStartedKey;
+
 extern const KeyRef coordinatorsKey;
 extern const KeyRef logsKey;
 extern const KeyRef minRequiredCommitVersionKey;

fdbrpc/Locality.cpp

@@ -135,6 +135,26 @@ ProcessClass::Fitness ProcessClass::machineClassFitness( ClusterRole role ) cons
 		default:
 			return ProcessClass::WorstFit;
 		}
+	case ProcessClass::Backup:
+		switch( _class ) {
+		case ProcessClass::BackupClass:
+			return ProcessClass::BestFit;
+		case ProcessClass::StatelessClass:
+		case ProcessClass::LogRouterClass:
+			return ProcessClass::GoodFit;
+		case ProcessClass::UnsetClass:
+			return ProcessClass::UnsetFit;
+		case ProcessClass::ResolutionClass:
+			return ProcessClass::OkayFit;
+		case ProcessClass::TransactionClass:
+			return ProcessClass::OkayFit;
+		case ProcessClass::CoordinatorClass:
+		case ProcessClass::MasterClass:
+		case ProcessClass::TesterClass:
+			return ProcessClass::NeverAssign;
+		default:
+			return ProcessClass::WorstFit;
+		}
 	case ProcessClass::ClusterController:
 		switch( _class ) {
 		case ProcessClass::ClusterControllerClass:

fdbrpc/Locality.h

@@ -44,11 +44,12 @@ struct ProcessClass {
 		CoordinatorClass,
 		RatekeeperClass,
 		StorageCacheClass,
+		BackupClass,
 		InvalidClass = -1
 	};
 
 	enum Fitness { BestFit, GoodFit, UnsetFit, OkayFit, WorstFit, ExcludeFit, NeverAssign }; //cannot be larger than 7 because of leader election mask
-	enum ClusterRole { Storage, TLog, Proxy, Master, Resolver, LogRouter, ClusterController, DataDistributor, Ratekeeper, StorageCache, NoRole };
+	enum ClusterRole { Storage, TLog, Proxy, Master, Resolver, LogRouter, ClusterController, DataDistributor, Ratekeeper, StorageCache, Backup, NoRole };
 	enum ClassSource { CommandLineSource, AutoSource, DBSource, InvalidSource = -1 };
 	int16_t _class;
 	int16_t _source;
@@ -74,6 +75,7 @@ public:
 		else if (s=="coordinator") _class = CoordinatorClass;
 		else if (s=="ratekeeper") _class = RatekeeperClass;
 		else if (s=="storage_cache") _class = StorageCacheClass;
+		else if (s=="backup") _class = BackupClass;
 		else _class = InvalidClass;
 	}
 
@@ -94,6 +96,7 @@ public:
 		else if (classStr=="coordinator") _class = CoordinatorClass;
 		else if (classStr=="ratekeeper") _class = RatekeeperClass;
 		else if (classStr=="storage_cache") _class = StorageCacheClass;
+		else if (classStr=="backup") _class = BackupClass;
 		else _class = InvalidClass;
 
 		if (sourceStr=="command_line") _source = CommandLineSource;
@@ -129,6 +132,7 @@ public:
 			case CoordinatorClass: return "coordinator";
 			case RatekeeperClass: return "ratekeeper";
 			case StorageCacheClass: return "storage_cache";
+			case BackupClass: return "backup";
 			default: return "invalid";
 		}
 	}

fdbrpc/simulator.h

@@ -99,6 +99,7 @@ public:
 				case ProcessClass::DataDistributorClass: return false;
 				case ProcessClass::RatekeeperClass: return false;
 				case ProcessClass::StorageCacheClass: return false;
+				case ProcessClass::BackupClass: return false;
 				default: return false;
 			}
 		}

fdbserver/BackupInterface.h

@@ -0,0 +1,54 @@
+/*
+ * BackupInterface.h
+ *
+ * This source file is part of the FoundationDB open source project
+ *
+ * Copyright 2013-2019 Apple Inc. and the FoundationDB project authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef FDBSERVER_BACKUPINTERFACE_H
+#define FDBSERVER_BACKUPINTERFACE_H
+
+#include "fdbclient/FDBTypes.h"
+#include "fdbrpc/fdbrpc.h"
+#include "fdbrpc/Locality.h"
+
+// The interface for backup workers.
+struct BackupInterface {
+	constexpr static FileIdentifier file_identifier = 6762745;
+	RequestStream<ReplyPromise<Void>> waitFailure;
+	struct LocalityData locality;
+
+	BackupInterface() = default;
+	explicit BackupInterface(const struct LocalityData& l) : locality(l) {}
+
+	void initEndpoints() {}
+	UID id() const { return getToken(); }
+	NetworkAddress address() const { return waitFailure.getEndpoint().getPrimaryAddress(); }
+	UID getToken() const { return waitFailure.getEndpoint().token; }
+	bool operator== (const BackupInterface& r) const {
+		return getToken() == r.getToken();
+	}
+	bool operator!= (const BackupInterface& r) const {
+		return !(*this == r);
+	}
+
+	template <class Archive>
+	void serialize(Archive& ar) {
+		serializer(ar, waitFailure, locality);
+	}
+};
+
+#endif //FDBSERVER_BACKUPINTERFACE_H

fdbserver/BackupProgress.actor.cpp

@@ -0,0 +1,117 @@
+#include "fdbserver/BackupProgress.actor.h"
+
+#include "fdbclient/NativeAPI.actor.h"
+#include "fdbclient/SystemData.h"
+#include "flow/UnitTest.h"
+#include "flow/actorcompiler.h" // This must be the last #include.
+
+void BackupProgress::addBackupStatus(const WorkerBackupStatus& status) {
+	auto& it = progress[status.epoch];
+	auto lb = it.lower_bound(status.tag);
+	if (lb != it.end() && status.tag == lb->first) {
+		if (lb->second < status.version) {
+			lb->second = status.version;
+		}
+	} else {
+		it.insert(lb, { status.tag, status.version });
+	}
+}
+
+std::map<std::pair<LogEpoch, Version>, std::map<Tag, Version>> BackupProgress::getUnfinishedBackup() {
+	std::map<std::pair<LogEpoch, Version>, std::map<Tag, Version>> toRecruit;
+
+	if (!backupStartedValue.present()) return toRecruit; // No active backups
+
+	for (const auto& [epoch, info] : epochInfos) {
+		std::set<Tag> tags = enumerateLogRouterTags(info.logRouterTags);
+		std::map<Tag, Version> tagVersions;
+		auto progressIt = progress.find(epoch);
+		if (progressIt != progress.end()) {
+			for (const auto& [tag, savedVersion] : progressIt->second) {
+				tags.erase(tag);
+				if (savedVersion < info.epochEnd - 1) {
+					tagVersions.insert({ tag, savedVersion + 1 });
+					TraceEvent("BW", dbgid)
+					    .detail("OldEpoch", epoch)
+					    .detail("Tag", tag.toString())
+					    .detail("BeginVersion", savedVersion + 1)
+					    .detail("EndVersion", info.epochEnd);
+				}
+			}
+		}
+		for (const Tag tag : tags) { // tags without progress data
+			tagVersions.insert({ tag, info.epochBegin });
+			TraceEvent("BW", dbgid)
+			    .detail("OldEpoch", epoch)
+			    .detail("Tag", tag.toString())
+			    .detail("BeginVersion", info.epochBegin)
+			    .detail("EndVersion", info.epochEnd);
+		}
+		if (!tagVersions.empty()) {
+			toRecruit[{ epoch, info.epochEnd }] = tagVersions;
+		}
+	}
+	return toRecruit;
+}
+
+// Save each tag's savedVersion for all epochs into "bStatus".
+ACTOR Future<Void> getBackupProgress(Database cx, UID dbgid, Reference<BackupProgress> bStatus) {
+	state Transaction tr(cx);
+
+	loop {
+		try {
+			tr.setOption(FDBTransactionOptions::ACCESS_SYSTEM_KEYS);
+			tr.setOption(FDBTransactionOptions::PRIORITY_SYSTEM_IMMEDIATE);
+			tr.setOption(FDBTransactionOptions::LOCK_AWARE);
+			state Future<Optional<Value>> fValue = tr.get(backupStartedKey);
+			state Standalone<RangeResultRef> results = wait(tr.getRange(backupProgressKeys, CLIENT_KNOBS->TOO_MANY));
+			ASSERT(!results.more && results.size() < CLIENT_KNOBS->TOO_MANY);
+
+			Optional<Value> value = wait(fValue);
+			bStatus->setBackupStartedValue(value);
+			for (auto& it : results) {
+				const UID workerID = decodeBackupProgressKey(it.key);
+				const WorkerBackupStatus status = decodeBackupProgressValue(it.value);
+				bStatus->addBackupStatus(status);
+				TraceEvent("GotBackupProgress", dbgid)
+				    .detail("W", workerID)
+				    .detail("Epoch", status.epoch)
+				    .detail("Version", status.version)
+				    .detail("Tag", status.tag.toString());
+			}
+			return Void();
+		} catch (Error& e) {
+			wait(tr.onError(e));
+		}
+	}
+}
+
+TEST_CASE("/BackupProgress/Unfinished") {
+	std::map<LogEpoch, ILogSystem::EpochTagsVersionsInfo> epochInfos;
+
+	const int epoch1 = 2, begin1 = 1, end1 = 100;
+	const Tag tag1(tagLocalityLogRouter, 0);
+	epochInfos.insert({ epoch1, ILogSystem::EpochTagsVersionsInfo(1, begin1, end1) });
+	BackupProgress progress(UID(0, 0), epochInfos);
+	progress.setBackupStartedValue(Optional<Value>(LiteralStringRef("1")));
+
+	std::map<std::pair<LogEpoch, Version>, std::map<Tag, Version>> unfinished = progress.getUnfinishedBackup();
+
+	ASSERT(unfinished.size() == 1);
+	for (const auto [epochVersion, tagVersion] : unfinished) {
+		ASSERT(epochVersion.first == epoch1 && epochVersion.second == end1);
+		ASSERT(tagVersion.size() == 1 && tagVersion.begin()->first == tag1 && tagVersion.begin()->second == begin1);
+	}
+
+	const int saved1 = 50;
+	WorkerBackupStatus status1(epoch1, saved1, tag1);
+	progress.addBackupStatus(status1);
+	unfinished = progress.getUnfinishedBackup();
+	ASSERT(unfinished.size() == 1);
+	for (const auto [epochVersion, tagVersion] : unfinished) {
+		ASSERT(epochVersion.first == epoch1 && epochVersion.second == end1);
+		ASSERT(tagVersion.size() == 1 && tagVersion.begin()->first == tag1 && tagVersion.begin()->second == saved1 + 1);
+	}
+
+	return Void();
+}

fdbserver/BackupProgress.actor.h

@@ -0,0 +1,89 @@
+/*
+ * BackupProgress.h
+ *
+ * This source file is part of the FoundationDB open source project
+ *
+ * Copyright 2013-2019 Apple Inc. and the FoundationDB project authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#if defined(NO_INTELLISENSE) && !defined(FDBSERVER_BACKUPPROGRESS_ACTOR_G_H)
+#define FDBSERVER_BACKUPPROGRESS_ACTOR_G_H
+#include "fdbserver/BackupProgress.actor.g.h"
+#elif !defined(FDBSERVER_BACKUPPROGRESS_ACTOR_H)
+#define FDBSERVER_BACKUPPROGRESS_ACTOR_H
+
+#include <map>
+#include "fdbclient/FDBTypes.h"
+#include "fdbserver/LogSystem.h"
+#include "flow/Arena.h"
+#include "flow/FastRef.h"
+#include "flow/actorcompiler.h" // This must be the last #include.
+
+class BackupProgress : NonCopyable, ReferenceCounted<BackupProgress> {
+public:
+	BackupProgress(UID id, const std::map<LogEpoch, ILogSystem::EpochTagsVersionsInfo>& infos)
+	  : dbgid(id), epochInfos(infos) {}
+	~BackupProgress() {}
+
+	// Adds a backup status. If the tag already has an entry, then the max of
+	// savedVersion is used.
+	void addBackupStatus(const WorkerBackupStatus& status);
+
+	// Returns a map of pair<Epoch, endVersion> : map<tag, savedVersion>, so that
+	// the backup range should be [savedVersion + 1, endVersion) for the "tag" of the "Epoch".
+	//
+	// Specifically, the backup ranges for each old epoch are:
+	//    if tag in tags_without_backup_progress:
+	//        backup [epochBegin, endVersion)
+	//    else if savedVersion < endVersion - 1 = knownCommittedVersion
+	//        backup [savedVersion + 1, endVersion)
+	std::map<std::pair<LogEpoch, Version>, std::map<Tag, Version>> getUnfinishedBackup();
+
+	// Set the value for "backupStartedKey"
+	void setBackupStartedValue(Optional<Value> value) {
+		backupStartedValue = value;
+	}
+
+	void addref() { ReferenceCounted<BackupProgress>::addref(); }
+
+	void delref() { ReferenceCounted<BackupProgress>::delref(); }
+
+private:
+	std::set<Tag> enumerateLogRouterTags(int logRouterTags) {
+		std::set<Tag> tags;
+		for (int i = 0; i < logRouterTags; i++) {
+			tags.insert(Tag(tagLocalityLogRouter, i));
+		}
+		return tags;
+	}
+
+	const UID dbgid;
+
+	// Note this MUST be iterated in ascending order.
+	const std::map<LogEpoch, ILogSystem::EpochTagsVersionsInfo> epochInfos;
+
+	// Backup progress saved in the system keyspace. Note there can be multiple
+	// progress status for a tag in an epoch due to later epoch trying to fill
+	// the gap. "progress" MUST be iterated in ascending order.
+	std::map<LogEpoch, std::map<Tag, Version>> progress;
+
+	// Value of the "backupStartedKey".
+	Optional<Value> backupStartedValue;
+};
+
+ACTOR Future<Void> getBackupProgress(Database cx, UID dbgid, Reference<BackupProgress> bStatus);
+
+#include "flow/unactorcompiler.h"
+#endif

fdbserver/BackupWorker.actor.cpp

@@ -0,0 +1,459 @@
+/*
+ * BackupWorker.actor.cpp
+ *
+ * This source file is part of the FoundationDB open source project
+ *
+ * Copyright 2013-2019 Apple Inc. and the FoundationDB project authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "fdbclient/BackupContainer.h"
+#include "fdbclient/DatabaseContext.h"
+#include "fdbclient/MasterProxyInterface.h"
+#include "fdbclient/SystemData.h"
+#include "fdbserver/BackupInterface.h"
+#include "fdbserver/LogProtocolMessage.h"
+#include "fdbserver/LogSystem.h"
+#include "fdbserver/ServerDBInfo.h"
+#include "fdbserver/WaitFailure.h"
+#include "fdbserver/WorkerInterface.actor.h"
+#include "flow/Error.h"
+
+#include "flow/actorcompiler.h"  // This must be the last #include.
+
+struct VersionedMessage {
+	LogMessageVersion version;
+	StringRef message;
+	VectorRef<Tag> tags;
+	Arena arena; // Keep a reference to the memory containing the message
+
+	VersionedMessage(LogMessageVersion v, StringRef m, const VectorRef<Tag>& t, const Arena& a)
+	  : version(v), message(m), tags(t), arena(a) {}
+	const Version getVersion() const { return version.version; }
+	const uint32_t getSubVersion() const { return version.sub; }
+};
+
+struct BackupData {
+	const UID myId;
+	const Tag tag; // LogRouter tag for this worker, i.e., (-2, i)
+	const Version startVersion;
+	const Optional<Version> endVersion; // old epoch's end version (inclusive), or empty for current epoch
+	const LogEpoch recruitedEpoch;
+	const LogEpoch backupEpoch;
+	Version minKnownCommittedVersion;
+	Version savedVersion, lastSeenVersion;
+	AsyncVar<Reference<ILogSystem>> logSystem;
+	Database cx;
+	std::vector<VersionedMessage> messages;
+	Reference<IBackupContainer> container;
+	AsyncVar<bool> pullFinished;
+
+	CounterCollection cc;
+	Future<Void> logger;
+
+	explicit BackupData(Reference<AsyncVar<ServerDBInfo>> db, const InitializeBackupRequest& req)
+	  : myId(req.reqId), tag(req.routerTag), startVersion(req.startVersion), endVersion(req.endVersion),
+	    recruitedEpoch(req.recruitedEpoch), backupEpoch(req.backupEpoch), minKnownCommittedVersion(invalidVersion),
+	    savedVersion(invalidVersion), lastSeenVersion(invalidVersion), cc("BackupWorker", myId.toString()) {
+		cx = openDBOnServer(db, TaskPriority::DefaultEndpoint, true, true);
+		pullFinished.set(false);
+
+		specialCounter(cc, "SavedVersion", [this]() { return this->savedVersion; });
+		specialCounter(cc, "MinKnownCommittedVersion", [this]() { return this->minKnownCommittedVersion; });
+		specialCounter(cc, "MsgQ", [this]() { return this->messages.size(); });
+		logger = traceCounters("BackupWorkerMetrics", myId, SERVER_KNOBS->WORKER_LOGGING_INTERVAL, &cc,
+		                       "BackupWorkerMetrics");
+		if (g_network->isSimulated()) {
+			container = IBackupContainer::openContainer("file://simfdb/mutation_backups/");
+		} else {
+			// TODO: use blobstore URL passed from somewhere.
+			ASSERT(false);
+			container = IBackupContainer::openContainer("blobstore://");
+		}
+	}
+
+	void pop() {
+		const LogEpoch oldest = logSystem.get()->getOldestBackupEpoch();
+		if (backupEpoch > oldest) {
+			// Defer pop if old epoch hasn't finished popping yet.
+			TraceEvent("BackupWorkerPopDeferred", myId)
+			    .suppressFor(1.0)
+			    .detail("BackupEpoch", backupEpoch)
+			    .detail("OldestEpoch", oldest)
+			    .detail("Version", savedVersion);
+			return;
+		}
+		const Tag popTag = logSystem.get()->getPseudoPopTag(tag, ProcessClass::BackupClass);
+		logSystem.get()->pop(savedVersion, popTag);
+	}
+
+	void eraseMessagesAfterEndVersion() {
+		ASSERT(endVersion.present());
+		const Version ver = endVersion.get();
+		while (!messages.empty()) {
+			if (messages.back().getVersion() > ver) {
+				messages.pop_back();
+			} else {
+				return;
+			}
+		}
+	}
+};
+
+ACTOR Future<Void> monitorBackupStarted(BackupData* self) {
+	loop {
+		state ReadYourWritesTransaction tr(self->cx);
+
+		loop {
+			try {
+				tr.setOption(FDBTransactionOptions::ACCESS_SYSTEM_KEYS);
+				tr.setOption(FDBTransactionOptions::LOCK_AWARE);
+				Optional<Standalone<StringRef>> value = wait(tr.get(backupStartedKey));
+				if (value.present()) return Void();
+
+				state Future<Void> watchFuture = tr.watch(backupStartedKey);
+				wait(tr.commit());
+				wait(watchFuture);
+				break;
+			} catch (Error& e) {
+				wait(tr.onError(e));
+			}
+		}
+	}
+}
+
+ACTOR Future<Void> saveProgress(BackupData* self, Version backupVersion) {
+	state Transaction tr(self->cx);
+	state Key key = backupProgressKeyFor(self->myId);
+
+	loop {
+		try {
+			tr.setOption(FDBTransactionOptions::ACCESS_SYSTEM_KEYS);
+			tr.setOption(FDBTransactionOptions::PRIORITY_SYSTEM_IMMEDIATE);
+			tr.setOption(FDBTransactionOptions::LOCK_AWARE);
+
+			WorkerBackupStatus status(self->backupEpoch, backupVersion, self->tag);
+			tr.set(key, backupProgressValue(status));
+			tr.addReadConflictRange(singleKeyRange(key));
+			wait(tr.commit());
+			return Void();
+		} catch (Error& e) {
+			wait(tr.onError(e));
+		}
+	}
+}
+
+static std::string tagsToString(const VectorRef<Tag>& tags) {
+	std::string s;
+	bool first = true;
+	for (auto t = tags.begin(); t != tags.end(); t++) {
+		if (first) {
+			first = false;
+		} else {
+			s.append(", ");
+		}
+		s.append((*t).toString());
+	}
+	return s;
+}
+
+// Returns true if the message is a mutation that should be backuped, i.e.,
+// either key is not in system key space or is not a metadataVersionKey.
+bool isBackupMessage(const VersionedMessage& msg) {
+	for (Tag tag : msg.tags) {
+		if (tag.locality == tagLocalitySpecial || tag.locality == tagLocalityTxs) {
+			return false; // skip Txs mutations
+		}
+	}
+
+	BinaryReader reader(msg.message.begin(), msg.message.size(), AssumeVersion(currentProtocolVersion));
+
+	// Return false for LogProtocolMessage.
+	if (LogProtocolMessage::isNextIn(reader)) return false;
+
+	MutationRef m;
+	reader >> m;
+
+	// check for metadataVersionKey and special metadata mutations
+	if (!normalKeys.contains(m.param1) && m.param1 != metadataVersionKey) {
+		return false;
+	}
+
+	return true;
+}
+
+// Return a block of contiguous padding bytes, growing if needed.
+static Value makePadding(int size) {
+	static Value pad;
+	if (pad.size() < size) {
+		pad = makeString(size);
+		memset(mutateString(pad), '\xff', pad.size());
+	}
+
+	return pad.substr(0, size);
+}
+
+// Saves messages in the range of [0, numMsg) to a file and then remove these
+// messages. The file format is a sequence of (Version, sub#, msgSize, message),
+ACTOR Future<Void> saveMutationsToFile(BackupData* self, Version popVersion, int numMsg) {
+	state int blockSize = SERVER_KNOBS->BACKUP_FILE_BLOCK_BYTES;
+	state Reference<IBackupFile> logFile =
+	    wait(self->container->writeTaggedLogFile(self->messages[0].getVersion(), popVersion, blockSize, self->tag.id));
+	TraceEvent("OpenMutationFile", self->myId)
+	    .detail("StartVersion", self->messages[0].getVersion())
+	    .detail("EndVersion", popVersion)
+	    .detail("BlockSize", blockSize)
+	    .detail("TagId", self->tag.id)
+	    .detail("File", logFile->getFileName());
+	state int idx = 0;
+	state int64_t blockEnd = 0;
+	for (; idx < numMsg; idx++) {
+		if (!isBackupMessage(self->messages[idx])) continue;
+
+		const int bytes = sizeof(Version) + sizeof(uint32_t) + sizeof(int) + self->messages[idx].message.size();
+		// Start a new block if needed
+		if (logFile->size() + bytes > blockEnd) {
+			// Write padding if needed
+			const int bytesLeft = blockEnd - logFile->size();
+			if (bytesLeft > 0) {
+				state Value paddingFFs = makePadding(bytesLeft);
+				wait(logFile->append(paddingFFs.begin(), bytesLeft));
+			}
+
+			blockEnd += blockSize;
+			// TODO: add block header
+		}
+
+		// Convert to big Endianness for version.version, version.sub, and msgSize
+		// The decoder assumes 0xFF is the end, so little endian can easily be
+		// mistaken as the end. In contrast, big endian for version almost guarantee
+		// the first byte is not 0xFF (should always be 0x00).
+		state int msgSize = self->messages[idx].message.size();
+		BinaryWriter wr(Unversioned());
+		wr << bigEndian64(self->messages[idx].version.version)
+		   << bigEndian32(self->messages[idx].version.sub)
+		   << bigEndian32(msgSize);
+		Standalone<StringRef> buf = wr.toValue();
+		wait(logFile->append((void*)buf.begin(), buf.size()));
+		wait(logFile->append(self->messages[idx].message.begin(), msgSize));
+	}
+
+	self->messages.erase(self->messages.begin(), self->messages.begin() + numMsg);
+	wait(logFile->finish());
+	TraceEvent("CloseMutationFile", self->myId)
+	    .detail("FileSize", logFile->size())
+	    .detail("TagId", self->tag.id)
+	    .detail("File", logFile->getFileName());
+
+	return Void();
+}
+
+// Uploads self->messages to cloud storage and updates savedVersion.
+ACTOR Future<Void> uploadData(BackupData* self) {
+	state Version popVersion = invalidVersion;
+
+	loop {
+		if (self->endVersion.present() && self->savedVersion >= self->endVersion.get()) {
+			self->messages.clear();
+			return Void();
+		}
+
+		// FIXME: knobify the delay of 10s. This delay is sensitive, as it is the
+		// lag TLog might have. Changing to 20s may fail consistency check.
+		state Future<Void> uploadDelay = delay(10);
+
+		if (self->messages.empty()) {
+			// Even though messages is empty, we still want to advance popVersion.
+			popVersion = std::max(popVersion, self->lastSeenVersion);
+		} else {
+			const Version maxPopVersion =
+			    self->endVersion.present() ? self->endVersion.get() : self->minKnownCommittedVersion;
+			int numMsg = 0;
+			for (const auto& message : self->messages) {
+				if (message.getVersion() > maxPopVersion) break;
+				popVersion = std::max(popVersion, message.getVersion());
+				numMsg++;
+			}
+			if (numMsg > 0) {
+				wait(saveMutationsToFile(self, popVersion, numMsg));
+			}
+		}
+		if (self->pullFinished.get() && self->messages.empty()) {
+			// Advance popVersion to the endVersion to avoid gap between last
+			// message version and the endVersion.
+			popVersion = self->endVersion.get();
+		}
+
+		if (popVersion > self->savedVersion) {
+			wait(saveProgress(self, popVersion));
+			TraceEvent("BackupWorkerSavedProgress", self->myId)
+			    .detail("Tag", self->tag.toString())
+			    .detail("Version", popVersion)
+			    .detail("MsgQ", self->messages.size());
+			self->savedVersion = std::max(popVersion, self->savedVersion);
+			self->pop();
+		}
+
+		if (!self->pullFinished.get()) {
+			wait(uploadDelay || self->pullFinished.onChange());
+		}
+	}
+}
+
+// Pulls data from TLog servers using LogRouter tag.
+ACTOR Future<Void> pullAsyncData(BackupData* self) {
+	state Future<Void> logSystemChange = Void();
+	state Reference<ILogSystem::IPeekCursor> r;
+	state Version tagAt = self->startVersion;
+	state Version lastVersion = 0;
+
+	loop {
+		loop choose {
+			when (wait(r ? r->getMore(TaskPriority::TLogCommit) : Never())) {
+				break;
+			}
+			when (wait(logSystemChange)) {
+				if (self->logSystem.get()) {
+					r = self->logSystem.get()->peekLogRouter(self->myId, tagAt, self->tag);
+				} else {
+					r = Reference<ILogSystem::IPeekCursor>();
+				}
+				logSystemChange = self->logSystem.onChange();
+			}
+		}
+		self->minKnownCommittedVersion = std::max(self->minKnownCommittedVersion, r->getMinKnownCommittedVersion());
+
+		// Note we aggressively peek (uncommitted) messages, but only committed
+		// messages/mutations will be flushed to disk/blob in uploadData().
+		while (r->hasMessage()) {
+			self->messages.emplace_back(r->version(), r->getMessage(), r->getTags(), r->arena());
+			r->nextMessage();
+		}
+
+		tagAt = std::max(r->version().version, lastVersion);
+		self->lastSeenVersion = std::max(tagAt, self->lastSeenVersion);
+		TraceEvent("BackupWorkerGot", self->myId).suppressFor(1.0).detail("V", tagAt);
+		if (self->endVersion.present() && tagAt > self->endVersion.get()) {
+			self->eraseMessagesAfterEndVersion();
+			TraceEvent("BackupWorkerFinishPull", self->myId)
+			    .detail("Tag", self->tag.toString())
+			    .detail("VersionGot", tagAt)
+			    .detail("EndVersion", self->endVersion.get())
+			    .detail("MsgQ", self->messages.size());
+			self->pullFinished.set(true);
+			return Void();
+		}
+		wait(yield());
+	}
+}
+
+ACTOR Future<Void> monitorBackupKeyOrPullData(BackupData* self) {
+	loop {
+		state Future<Void> started = monitorBackupStarted(self);
+
+		loop {
+			GetReadVersionRequest request(1, GetReadVersionRequest::PRIORITY_DEFAULT |
+			                                     GetReadVersionRequest::FLAG_USE_MIN_KNOWN_COMMITTED_VERSION);
+
+			choose {
+				when(wait(started)) { break; }
+				when(wait(self->cx->onMasterProxiesChanged())) {}
+				when(GetReadVersionReply reply = wait(loadBalance(self->cx->getMasterProxies(false),
+				                                                  &MasterProxyInterface::getConsistentReadVersion,
+				                                                  request, self->cx->taskID))) {
+					self->savedVersion = std::max(reply.version, self->savedVersion);
+					self->minKnownCommittedVersion = std::max(reply.version, self->minKnownCommittedVersion);
+					self->pop(); // Pop while the worker is in this NOOP state.
+					wait(delay(SERVER_KNOBS->BACKUP_NOOP_POP_DELAY, self->cx->taskID));
+				}
+			}
+		}
+
+		TraceEvent("BackupWorkerStartPullData", self->myId);
+		wait(pullAsyncData(self));
+	}
+}
+
+ACTOR Future<Void> checkRemoved(Reference<AsyncVar<ServerDBInfo>> db, LogEpoch recoveryCount,
+                                BackupData* self) {
+	loop {
+		bool isDisplaced =
+		    db->get().recoveryCount > recoveryCount && db->get().recoveryState != RecoveryState::UNINITIALIZED;
+		if (isDisplaced) {
+			TraceEvent("BackupWorkerDisplaced", self->myId)
+			    .detail("RecoveryCount", recoveryCount)
+			    .detail("SavedVersion", self->savedVersion)
+			    .detail("BackupWorkers", describe(db->get().logSystemConfig.tLogs))
+			    .detail("DBRecoveryCount", db->get().recoveryCount)
+			    .detail("RecoveryState", (int)db->get().recoveryState);
+			throw worker_removed();
+		}
+		wait(db->onChange());
+	}
+}
+
+ACTOR Future<Void> backupWorker(BackupInterface interf, InitializeBackupRequest req,
+                                Reference<AsyncVar<ServerDBInfo>> db) {
+	state BackupData self(db, req);
+	state PromiseStream<Future<Void>> addActor;
+	state Future<Void> error = actorCollection(addActor.getFuture());
+	state Future<Void> dbInfoChange = Void();
+
+	TraceEvent("BackupWorkerStart", self.myId)
+	    .detail("Tag", req.routerTag.toString())
+	    .detail("StartVersion", req.startVersion)
+	    .detail("EndVersion", req.endVersion.present() ? req.endVersion.get() : -1)
+	    .detail("LogEpoch", req.recruitedEpoch)
+	    .detail("BackupEpoch", req.backupEpoch);
+	try {
+		addActor.send(monitorBackupKeyOrPullData(&self));
+		addActor.send(checkRemoved(db, req.recruitedEpoch, &self));
+		addActor.send(waitFailureServer(interf.waitFailure.getFuture()));
+
+		state Future<Void> done = uploadData(&self);
+
+		loop choose {
+			when(wait(dbInfoChange)) {
+				dbInfoChange = db->onChange();
+				Reference<ILogSystem> ls = ILogSystem::fromServerDBInfo(self.myId, db->get(), true);
+				bool hasPseudoLocality = ls.isValid() && ls->hasPseudoLocality(tagLocalityBackup);
+				LogEpoch oldestBackupEpoch = 0;
+				if (hasPseudoLocality) {
+					self.logSystem.set(ls);
+					self.pop();
+					oldestBackupEpoch = ls->getOldestBackupEpoch();
+				}
+				TraceEvent("BackupWorkerLogSystem", self.myId)
+				    .detail("HasBackupLocality", hasPseudoLocality)
+				    .detail("OldestBackupEpoch", oldestBackupEpoch)
+				    .detail("Tag", self.tag.toString());
+			}
+			when(wait(done)) {
+				TraceEvent("BackupWorkerDone", self.myId).detail("BackupEpoch", self.backupEpoch);
+				// Notify master so that this worker can be removed from log system, then this
+				// worker (for an old epoch's unfinished work) can safely exit.
+				wait(brokenPromiseToNever(db->get().master.notifyBackupWorkerDone.getReply(
+				    BackupWorkerDoneRequest(self.myId, self.backupEpoch))));
+				break;
+			}
+			when(wait(error)) {}
+		}
+	} catch (Error& e) {
+		TraceEvent("BackupWorkerTerminated", self.myId).error(e, true);
+		if (e.code() != error_code_actor_cancelled && e.code() != error_code_worker_removed) {
+			throw;
+		}
+	}
+	return Void();
+}

fdbserver/CMakeLists.txt

@@ -1,6 +1,10 @@
 set(FDBSERVER_SRCS
   ApplyMetadataMutation.h
   ApplyMetadataMutation.cpp
+  BackupInterface.h
+  BackupProgress.actor.cpp
+  BackupProgress.actor.h
+  BackupWorker.actor.cpp
   ClusterController.actor.cpp
   ClusterRecruitmentInterface.h
   ConflictSet.h

fdbserver/ClusterController.actor.cpp

@@ -18,9 +18,16 @@
  * limitations under the License.
  */
 
+#include <algorithm>
+#include <iterator>
+#include <map>
+#include <set>
+#include <vector>
+
 #include "fdbrpc/FailureMonitor.h"
 #include "flow/ActorCollection.h"
 #include "fdbclient/NativeAPI.actor.h"
+#include "fdbserver/BackupInterface.h"
 #include "fdbserver/CoordinationInterface.h"
 #include "fdbserver/DataDistributorInterface.h"
 #include "fdbserver/Knobs.h"
@@ -34,7 +41,6 @@
 #include "fdbserver/ServerDBInfo.h"
 #include "fdbserver/Status.h"
 #include "fdbserver/LatencyBandConfig.h"
-#include <algorithm>
 #include "fdbclient/DatabaseContext.h"
 #include "fdbserver/RecoveryState.h"
 #include "fdbclient/ReadYourWrites.h"
@@ -186,6 +192,7 @@ public:
 			}
 			serverInfo->set( newInfoCache );
 		}
+
 	};
 
 	struct UpdateWorkerList {
@@ -773,6 +780,14 @@ public:
 			}
 		}
 
+		const int nBackup = std::max<int>(
+		    (req.configuration.desiredLogRouterCount > 0 ? req.configuration.desiredLogRouterCount : tlogs.size()),
+		    req.maxOldLogRouters);
+		auto backupWorkers =
+		    getWorkersForRoleInDatacenter(dcId, ProcessClass::Backup, nBackup, req.configuration, id_used);
+		std::transform(backupWorkers.begin(), backupWorkers.end(), std::back_inserter(result.backupWorkers),
+		               [](const WorkerDetails& w) { return w.interf; });
+
 		if( now() - startTime < SERVER_KNOBS->WAIT_FOR_GOOD_RECRUITMENT_DELAY &&
 			( RoleFitness(SERVER_KNOBS->EXPECTED_TLOG_FITNESS, req.configuration.getDesiredLogs(), ProcessClass::TLog).betterCount(RoleFitness(tlogs, ProcessClass::TLog)) ||
 			  ( region.satelliteTLogReplicationFactor > 0 && RoleFitness(SERVER_KNOBS->EXPECTED_TLOG_FITNESS, req.configuration.getDesiredSatelliteLogs(dcId), ProcessClass::TLog).betterCount(RoleFitness(satelliteLogs, ProcessClass::TLog)) ) ||
@@ -898,6 +913,14 @@ public:
 							result.resolvers.push_back(resolvers[i].interf);
 						for(int i = 0; i < proxies.size(); i++)
 							result.proxies.push_back(proxies[i].interf);
+
+						const int nBackup = std::max<int>(tlogs.size(), req.maxOldLogRouters);
+						auto backupWorkers = getWorkersForRoleInDatacenter(dcId, ProcessClass::Backup, nBackup,
+						                                                   req.configuration, id_used);
+						std::transform(backupWorkers.begin(), backupWorkers.end(),
+						               std::back_inserter(result.backupWorkers),
+						               [](const WorkerDetails& w) { return w.interf; });
+
 						break;
 					} else {
 						if(fitness < bestFitness) {
@@ -1014,6 +1037,8 @@ public:
 		std::vector<WorkerDetails> satellite_tlogs;
 		std::vector<WorkerDetails> log_routers;
 		std::set<NetworkAddress> logRouterAddresses;
+		std::vector<WorkerDetails> backup_workers;
+		std::set<NetworkAddress> backup_addresses;
 
 		for( auto& logSet : dbi.logSystemConfig.tLogs ) {
 			for( auto& it : logSet.tLogs ) {
@@ -1044,6 +1069,16 @@ public:
 					log_routers.push_back(tlogWorker->second.details);
 				}
 			}
+
+			for (const auto& worker : logSet.backupWorkers) {
+				auto workerIt = id_worker.find(worker.interf().locality.processId());
+				if (workerIt == id_worker.end()) return false;
+				if (workerIt->second.priorityInfo.isExcluded) return true;
+				if (backup_addresses.count(workerIt->second.details.interf.address()) == 0) {
+					backup_addresses.insert(workerIt->second.details.interf.address());
+					backup_workers.push_back(workerIt->second.details);
+				}
+			}
 		}
 
 		// Get proxy classes
@@ -1201,15 +1236,36 @@ public:
 		if(oldInFit.proxy.betterFitness(newInFit.proxy) || oldInFit.resolver.betterFitness(newInFit.resolver)) {
 			return false;
 		}
-		if(oldTLogFit > newTLogFit || oldInFit > newInFit || oldSatelliteTLogFit > newSatelliteTLogFit || oldRemoteTLogFit > newRemoteTLogFit || oldLogRoutersFit > newLogRoutersFit) {
-			TraceEvent("BetterMasterExists", id).detail("OldMasterFit", oldMasterFit).detail("NewMasterFit", newMasterFit)
-				.detail("OldTLogFit", oldTLogFit.toString()).detail("NewTLogFit", newTLogFit.toString())
-				.detail("OldProxyFit", oldInFit.proxy.toString()).detail("NewProxyFit", newInFit.proxy.toString())
-				.detail("OldResolverFit", oldInFit.resolver.toString()).detail("NewResolverFit", newInFit.resolver.toString())
-				.detail("OldSatelliteFit", oldSatelliteTLogFit.toString()).detail("NewSatelliteFit", newSatelliteTLogFit.toString())
-				.detail("OldRemoteFit", oldRemoteTLogFit.toString()).detail("NewRemoteFit", newRemoteTLogFit.toString())
-				.detail("OldRouterFit", oldLogRoutersFit.toString()).detail("NewRouterFit", newLogRoutersFit.toString())
-				.detail("OldSatelliteFallback", oldSatelliteFallback).detail("NewSatelliteFallback", newSatelliteFallback);
+
+		// Check backup worker fitness
+		RoleFitness oldBackupWorkersFit(backup_workers, ProcessClass::Backup);
+		const int nBackup = backup_addresses.size();
+		RoleFitness newBackupWorkersFit(
+		    getWorkersForRoleInDatacenter(clusterControllerDcId, ProcessClass::Backup, nBackup, db.config, id_used),
+		    ProcessClass::Backup);
+
+		if (oldTLogFit > newTLogFit || oldInFit > newInFit || oldSatelliteTLogFit > newSatelliteTLogFit ||
+		    oldRemoteTLogFit > newRemoteTLogFit || oldLogRoutersFit > newLogRoutersFit ||
+		    oldBackupWorkersFit > newBackupWorkersFit) {
+			TraceEvent("BetterMasterExists", id)
+			    .detail("OldMasterFit", oldMasterFit)
+			    .detail("NewMasterFit", newMasterFit)
+			    .detail("OldTLogFit", oldTLogFit.toString())
+			    .detail("NewTLogFit", newTLogFit.toString())
+			    .detail("OldProxyFit", oldInFit.proxy.toString())
+			    .detail("NewProxyFit", newInFit.proxy.toString())
+			    .detail("OldResolverFit", oldInFit.resolver.toString())
+			    .detail("NewResolverFit", newInFit.resolver.toString())
+			    .detail("OldSatelliteFit", oldSatelliteTLogFit.toString())
+			    .detail("NewSatelliteFit", newSatelliteTLogFit.toString())
+			    .detail("OldRemoteFit", oldRemoteTLogFit.toString())
+			    .detail("NewRemoteFit", newRemoteTLogFit.toString())
+			    .detail("OldRouterFit", oldLogRoutersFit.toString())
+			    .detail("NewRouterFit", newLogRoutersFit.toString())
+			    .detail("OldBackupWorkerFit", oldBackupWorkersFit.toString())
+			    .detail("NewBackupWorkerFit", newBackupWorkersFit.toString())
+			    .detail("OldSatelliteFallback", oldSatelliteFallback)
+			    .detail("NewSatelliteFallback", newSatelliteFallback);
 			return true;
 		}
 
@@ -1293,8 +1349,8 @@ public:
 	double startTime;
 	Optional<double> remoteStartTime;
 	Version datacenterVersionDifference;
-	bool versionDifferenceUpdated;
 	PromiseStream<Future<Void>> addActor;
+	bool versionDifferenceUpdated;
 	bool recruitingDistributor;
 	Optional<UID> recruitingRatekeeperID;
 	AsyncVar<bool> recruitRatekeeper;
@@ -2155,12 +2211,15 @@ void registerWorker( RegisterWorkerRequest req, ClusterControllerData *self ) {
 	if (req.ratekeeperInterf.present()) {
 		if((self->recruitingRatekeeperID.present() && self->recruitingRatekeeperID.get() != req.ratekeeperInterf.get().id()) ||
 			self->clusterControllerDcId != w.locality.dcId()) {
-				TraceEvent("CCHaltRegisteringRatekeeper", self->id).detail("RKID", req.ratekeeperInterf.get().id())
-			.detail("DcID", printable(self->clusterControllerDcId))
-			.detail("ReqDcID", printable(w.locality.dcId()))
-			.detail("RecruitingRKID", self->recruitingRatekeeperID.present() ? self->recruitingRatekeeperID.get() : UID());
-			self->id_worker[w.locality.processId()].haltRatekeeper = brokenPromiseToNever(req.ratekeeperInterf.get().haltRatekeeper.getReply(HaltRatekeeperRequest(self->id)));
-		} else if(!self->recruitingRatekeeperID.present()) {
+			TraceEvent("CCHaltRegisteringRatekeeper", self->id)
+			    .detail("RKID", req.ratekeeperInterf.get().id())
+			    .detail("DcID", printable(self->clusterControllerDcId))
+			    .detail("ReqDcID", printable(w.locality.dcId()))
+			    .detail("RecruitingRKID",
+			            self->recruitingRatekeeperID.present() ? self->recruitingRatekeeperID.get() : UID());
+			self->id_worker[w.locality.processId()].haltRatekeeper = brokenPromiseToNever(
+			    req.ratekeeperInterf.get().haltRatekeeper.getReply(HaltRatekeeperRequest(self->id)));
+		} else if (!self->recruitingRatekeeperID.present()) {
 			const RatekeeperInterface& rki = req.ratekeeperInterf.get();
 			const auto& ratekeeper = self->db.serverInfo->get().read().ratekeeper;
 			TraceEvent("CCRegisterRatekeeper", self->id).detail("RKID", rki.id());

fdbserver/ClusterRecruitmentInterface.h

@@ -22,10 +22,13 @@
 #define FDBSERVER_CLUSTERRECRUITMENTINTERFACE_H
 #pragma once
 
+#include <vector>
+
 #include "fdbclient/ClusterInterface.h"
 #include "fdbclient/StorageServerInterface.h"
 #include "fdbclient/MasterProxyInterface.h"
 #include "fdbclient/DatabaseConfiguration.h"
+#include "fdbserver/BackupInterface.h"
 #include "fdbserver/DataDistributorInterface.h"
 #include "fdbserver/MasterInterface.h"
 #include "fdbserver/RecoveryState.h"
@@ -84,20 +87,22 @@ struct ClusterControllerFullInterface {
 
 struct RecruitFromConfigurationReply {
 	constexpr static FileIdentifier file_identifier = 2224085;
-	vector<WorkerInterface> tLogs;
-	vector<WorkerInterface> satelliteTLogs;
-	vector<WorkerInterface> proxies;
-	vector<WorkerInterface> resolvers;
-	vector<WorkerInterface> storageServers;
-	vector<WorkerInterface> oldLogRouters;
+	std::vector<WorkerInterface> backupWorkers;
+	std::vector<WorkerInterface> tLogs;
+	std::vector<WorkerInterface> satelliteTLogs;
+	std::vector<WorkerInterface> proxies;
+	std::vector<WorkerInterface> resolvers;
+	std::vector<WorkerInterface> storageServers;
+	std::vector<WorkerInterface> oldLogRouters;
 	Optional<Key> dcId;
 	bool satelliteFallback;
 
 	RecruitFromConfigurationReply() : satelliteFallback(false) {}
 
 	template <class Ar>
-	void serialize( Ar& ar ) {
-		serializer(ar, tLogs, satelliteTLogs, proxies, resolvers, storageServers, oldLogRouters, dcId, satelliteFallback);
+	void serialize(Ar& ar) {
+		serializer(ar, tLogs, satelliteTLogs, proxies, resolvers, storageServers, oldLogRouters, dcId,
+		           satelliteFallback, backupWorkers);
 	}
 };
 
@@ -120,8 +125,8 @@ struct RecruitFromConfigurationRequest {
 
 struct RecruitRemoteFromConfigurationReply {
 	constexpr static FileIdentifier file_identifier = 9091392;
-	vector<WorkerInterface> remoteTLogs;
-	vector<WorkerInterface> logRouters;
+	std::vector<WorkerInterface> remoteTLogs;
+	std::vector<WorkerInterface> logRouters;
 
 	template <class Ar>
 	void serialize( Ar& ar ) {
@@ -230,18 +235,18 @@ struct RegisterMasterRequest {
 	UID id;
 	LocalityData mi;
 	LogSystemConfig logSystemConfig;
-	vector<MasterProxyInterface> proxies;
-	vector<ResolverInterface> resolvers;
+	std::vector<MasterProxyInterface> proxies;
+	std::vector<ResolverInterface> resolvers;
 	DBRecoveryCount recoveryCount;
 	int64_t registrationCount;
 	Optional<DatabaseConfiguration> configuration;
-	vector<UID> priorCommittedLogServers;
+	std::vector<UID> priorCommittedLogServers;
 	RecoveryState recoveryState;
 	bool recoveryStalled;
 
 	ReplyPromise<Void> reply;
 
-	RegisterMasterRequest() {}
+	RegisterMasterRequest() : logSystemConfig(0) {}
 
 	template <class Ar>
 	void serialize(Ar& ar) {

fdbserver/DBCoreState.h

@@ -41,9 +41,8 @@ struct OldLogData;
 // At the moment, transaction logs are replicated but not partitioned, so the topology is as simple as a list of
 //   transaction log replicas and the write quorum that was used to commit to them.  The read quorum required to
 //   ensure durability of locking and recovery is therefore tLogWriteAntiQuorum + 1.
-
 struct CoreTLogSet {
-	std::vector< UID > tLogs;
+	std::vector<UID> tLogs;
 	int32_t tLogWriteAntiQuorum; // The write anti quorum previously used to write to tLogs, which might be different from the anti quorum suggested by the current configuration going forward!
 	int32_t tLogReplicationFactor; // The replication factor previously used to write to tLogs, which might be different from the current configuration
 	std::vector< LocalityData > tLogLocalities; // Stores the localities of the log servers
@@ -57,9 +56,13 @@ struct CoreTLogSet {
 	CoreTLogSet() : tLogWriteAntiQuorum(0), tLogReplicationFactor(0), isLocal(true), locality(tagLocalityUpgraded), startVersion(invalidVersion) {}
 	explicit CoreTLogSet(const LogSet& logset);
 
-	bool operator == (CoreTLogSet const& rhs) const { 
-		return tLogs == rhs.tLogs && tLogWriteAntiQuorum == rhs.tLogWriteAntiQuorum && tLogReplicationFactor == rhs.tLogReplicationFactor && isLocal == rhs.isLocal && satelliteTagLocations == rhs.satelliteTagLocations &&
-			locality == rhs.locality && startVersion == rhs.startVersion && ((!tLogPolicy && !rhs.tLogPolicy) || (tLogPolicy && rhs.tLogPolicy && (tLogPolicy->info() == rhs.tLogPolicy->info())));
+	bool operator==(CoreTLogSet const& rhs) const {
+		return tLogs == rhs.tLogs && tLogWriteAntiQuorum == rhs.tLogWriteAntiQuorum &&
+		       tLogReplicationFactor == rhs.tLogReplicationFactor && isLocal == rhs.isLocal &&
+		       satelliteTagLocations == rhs.satelliteTagLocations && locality == rhs.locality &&
+		       startVersion == rhs.startVersion &&
+		       ((!tLogPolicy && !rhs.tLogPolicy) ||
+		        (tLogPolicy && rhs.tLogPolicy && (tLogPolicy->info() == rhs.tLogPolicy->info())));
 	}
 
 	template <class Archive>
@@ -77,14 +80,17 @@ struct OldTLogCoreData {
 	std::vector<CoreTLogSet> tLogs;
 	int32_t logRouterTags;
 	int32_t txsTags;
-	Version epochEnd;
+	Version epochBegin, epochEnd;
 	std::set<int8_t> pseudoLocalities;
+	LogEpoch epoch;
 
-	OldTLogCoreData() : epochEnd(0), logRouterTags(0), txsTags(0) {}
+	OldTLogCoreData() : epochBegin(0), epochEnd(0), logRouterTags(0), txsTags(0), epoch(0) {}
 	explicit OldTLogCoreData(const OldLogData&);
 
-	bool operator == (OldTLogCoreData const& rhs) const { 
-		return tLogs == rhs.tLogs && logRouterTags == rhs.logRouterTags && txsTags == rhs.txsTags && epochEnd == rhs.epochEnd && pseudoLocalities == rhs.pseudoLocalities;
+	bool operator==(const OldTLogCoreData& rhs) const {
+		return tLogs == rhs.tLogs && logRouterTags == rhs.logRouterTags && txsTags == rhs.txsTags &&
+		       epochBegin == rhs.epochBegin && epochEnd == rhs.epochEnd && pseudoLocalities == rhs.pseudoLocalities &&
+		       epoch == rhs.epoch;
 	}
 
 	template <class Archive>
@@ -103,6 +109,9 @@ struct OldTLogCoreData {
 		if (ar.protocolVersion().hasShardedTxsTags()) {
 			serializer(ar, txsTags);
 		}
+		if (ar.protocolVersion().hasBackupWorker()) {
+			serializer(ar, epoch, epochBegin);
+		}
 	}
 };
 
@@ -134,10 +143,12 @@ struct DBCoreState {
 		return priorCommittedLogServers;
 	}
 
-	bool isEqual(DBCoreState const& r) const {
-		return logSystemType == r.logSystemType && recoveryCount == r.recoveryCount && tLogs == r.tLogs && oldTLogData == r.oldTLogData && logRouterTags == r.logRouterTags && txsTags == r.txsTags && pseudoLocalities == r.pseudoLocalities;
+	bool isEqual(const DBCoreState& r) const {
+		return logSystemType == r.logSystemType && recoveryCount == r.recoveryCount && tLogs == r.tLogs &&
+		       oldTLogData == r.oldTLogData && logRouterTags == r.logRouterTags && txsTags == r.txsTags &&
+		       pseudoLocalities == r.pseudoLocalities;
 	}
-	bool operator == ( const DBCoreState& rhs ) const { return isEqual(rhs); }
+	bool operator==(const DBCoreState& rhs) const { return isEqual(rhs); }
 
 	template <class Archive>
 	void serialize(Archive& ar) {

fdbserver/Knobs.cpp

@@ -354,6 +354,11 @@ ServerKnobs::ServerKnobs(bool randomize, ClientKnobs* clientKnobs, bool isSimula
 	init( RESOLVER_STATE_MEMORY_LIMIT,                           1e6 );
 	init( LAST_LIMITED_RATIO,                                    2.0 );
 
+	// Backup Worker
+	init( BACKUP_TIMEOUT,                                        0.4 );
+	init( BACKUP_NOOP_POP_DELAY,                                 5.0 );
+	init( BACKUP_FILE_BLOCK_BYTES,                       1024 * 1024 );
+
 	//Cluster Controller
 	init( CLUSTER_CONTROLLER_LOGGING_DELAY,                      5.0 );
 	init( MASTER_FAILURE_REACTION_TIME,                          0.4 ); if( randomize && BUGGIFY ) MASTER_FAILURE_REACTION_TIME = 10.0;

fdbserver/Knobs.h

@@ -292,6 +292,11 @@ public:
 	double SAMPLE_POLL_TIME;
 	int64_t RESOLVER_STATE_MEMORY_LIMIT;
 
+	// Backup Worker
+	double BACKUP_TIMEOUT;  // master's reaction time for backup failure
+	double BACKUP_NOOP_POP_DELAY;
+	int BACKUP_FILE_BLOCK_BYTES;
+
 	//Cluster Controller
 	double CLUSTER_CONTROLLER_LOGGING_DELAY;
 	double MASTER_FAILURE_REACTION_TIME;

fdbserver/LogRouter.actor.cpp

@@ -73,11 +73,11 @@ struct LogRouterData {
 		}
 	};
 
-	UID dbgid;
+	const UID dbgid;
 	Reference<AsyncVar<Reference<ILogSystem>>> logSystem;
 	NotifiedVersion version;
 	NotifiedVersion minPopped;
-	Version startVersion;
+	const Version startVersion;
 	Version minKnownCommittedVersion;
 	Version poppedVersion;
 	Deque<std::pair<Version, Standalone<VectorRef<uint8_t>>>> messageBlocks;
@@ -108,7 +108,7 @@ struct LogRouterData {
 
 	//only callable after getTagData returns a null reference
 	Reference<TagData> createTagData(Tag tag, Version popped, Version knownCommittedVersion) {
-		Reference<TagData> newTagData = Reference<TagData>( new TagData(tag, popped, knownCommittedVersion) );
+		Reference<TagData> newTagData(new TagData(tag, popped, knownCommittedVersion));
 		tag_data[tag.id] = newTagData;
 		return newTagData;
 	}
@@ -221,21 +221,18 @@ ACTOR Future<Void> pullAsyncData( LogRouterData *self ) {
 	state Reference<ILogSystem::IPeekCursor> r;
 	state Version tagAt = self->version.get() + 1;
 	state Version lastVer = 0;
-	state std::vector<int> tags;
+	state std::vector<int> tags; // an optimization to avoid reallocating vector memory in every loop
 
 	loop {
-		loop {
-			choose {
-				when(wait( r ? r->getMore(TaskPriority::TLogCommit) : Never() ) ) {
-					break;
-				}
-				when( wait( dbInfoChange ) ) { //FIXME: does this actually happen?
-					if( self->logSystem->get() )
-						r = self->logSystem->get()->peekLogRouter( self->dbgid, tagAt, self->routerTag );
-					else
-						r = Reference<ILogSystem::IPeekCursor>();
-					dbInfoChange = self->logSystem->onChange();
+		loop choose {
+			when(wait(r ? r->getMore(TaskPriority::TLogCommit) : Never())) { break; }
+			when(wait(dbInfoChange)) { // FIXME: does this actually happen?
+				if (self->logSystem->get()) {
+					r = self->logSystem->get()->peekLogRouter(self->dbgid, tagAt, self->routerTag);
+				} else {
+					r = Reference<ILogSystem::IPeekCursor>();
 				}
+				dbInfoChange = self->logSystem->onChange();
 			}
 		}
 
@@ -537,26 +534,11 @@ ACTOR Future<Void> logRouterCore(
 }
 
 ACTOR Future<Void> checkRemoved(Reference<AsyncVar<ServerDBInfo>> db, uint64_t recoveryCount, TLogInterface myInterface) {
-	loop{
-		bool isDisplaced = ( (db->get().recoveryCount > recoveryCount && db->get().recoveryState != RecoveryState::UNINITIALIZED) || (db->get().recoveryCount == recoveryCount && db->get().recoveryState == RecoveryState::FULLY_RECOVERED) );
-		if(isDisplaced) {
-			for(auto& log : db->get().logSystemConfig.tLogs) {
-				if( std::count( log.logRouters.begin(), log.logRouters.end(), myInterface.id() ) ) {
-					isDisplaced = false;
-					break;
-				}
-			}
-		}
-		if(isDisplaced) {
-			for(auto& old : db->get().logSystemConfig.oldTLogs) {
-				for(auto& log : old.tLogs) {
-					 if( std::count( log.logRouters.begin(), log.logRouters.end(), myInterface.id() ) ) {
-						isDisplaced = false;
-						break;
-					 }
-				}
-			}
-		}
+	loop {
+		bool isDisplaced =
+		    ((db->get().recoveryCount > recoveryCount && db->get().recoveryState != RecoveryState::UNINITIALIZED) ||
+		     (db->get().recoveryCount == recoveryCount && db->get().recoveryState == RecoveryState::FULLY_RECOVERED));
+		isDisplaced = isDisplaced && !db->get().logSystemConfig.hasLogRouter(myInterface.id());
 		if (isDisplaced) {
 			throw worker_removed();
 		}

fdbserver/LogSystem.h

@@ -41,6 +41,7 @@ class LogSet : NonCopyable, public ReferenceCounted<LogSet> {
 public:
 	std::vector<Reference<AsyncVar<OptionalInterface<TLogInterface>>>> logServers;
 	std::vector<Reference<AsyncVar<OptionalInterface<TLogInterface>>>> logRouters;
+	std::vector<Reference<AsyncVar<OptionalInterface<BackupInterface>>>> backupWorkers;
 	int32_t tLogWriteAntiQuorum;
 	int32_t tLogReplicationFactor;
 	std::vector< LocalityData > tLogLocalities; // Stores the localities of the log servers
@@ -70,7 +71,7 @@ public:
 		return result;
 	}
 
-	bool hasLogRouter(UID id) {
+	bool hasLogRouter(UID id) const {
 		for (const auto& router : logRouters) {
 			if (router->get().id() == id) {
 				return true;
@@ -79,6 +80,15 @@ public:
 		return false;
 	}
 
+	bool hasBackupWorker(UID id) const {
+		for (const auto& worker : backupWorkers) {
+			if (worker->get().id() == id) {
+				return true;
+			}
+		}
+		return false;
+	}
+
 	std::string logServerString() {
 		std::string result;
 		for(int i = 0; i < logServers.size(); i++) {
@@ -704,6 +714,19 @@ struct ILogSystem {
 		// Call only on an ILogSystem obtained from recoverAndEndEpoch()
 		// Returns the first unreadable version number of the recovered epoch (i.e. message version numbers < (get_end(), 0) will be readable)
 
+	virtual Version getStartVersion() const = 0; // Returns the start version of current epoch.
+
+	struct EpochTagsVersionsInfo {
+		int32_t logRouterTags; // Number of log router tags.
+		Version epochBegin, epochEnd;
+
+		explicit EpochTagsVersionsInfo(int32_t n, Version begin, Version end)
+		  : logRouterTags(n), epochBegin(begin), epochEnd(end) {}
+	};
+
+	// Returns EpochTagVersionsInfo for old epochs that this log system is aware of, excluding the current epoch.
+	virtual std::map<LogEpoch, EpochTagsVersionsInfo> getOldEpochTagsVersionsInfo() const = 0;
+
 	virtual Future<Reference<ILogSystem>> newEpoch( struct RecruitFromConfigurationReply const& recr, Future<struct RecruitRemoteFromConfigurationReply> const& fRemoteWorkers, DatabaseConfiguration const& config,
 		LogEpoch recoveryCount, int8_t primaryLocality, int8_t remoteLocality, std::vector<Tag> const& allTags, Reference<AsyncVar<bool>> const& recruitmentStalled ) = 0;
 		// Call only on an ILogSystem obtained from recoverAndEndEpoch()
@@ -726,6 +749,7 @@ struct ILogSystem {
 	virtual bool hasRemoteLogs() const = 0;
 
 	virtual Tag getRandomRouterTag() const = 0;
+	virtual int getLogRouterTags() const = 0; // Returns the number of router tags.
 
 	virtual Tag getRandomTxsTag() const = 0;
 
@@ -739,9 +763,20 @@ struct ILogSystem {
 	// process class doesn't use pseudo tag, return the same tag.
 	virtual Tag getPseudoPopTag(Tag tag, ProcessClass::ClassType type) = 0;
 
-	virtual bool isPseudoLocality(int8_t locality) = 0;
+	virtual bool hasPseudoLocality(int8_t locality) = 0;
 
-	virtual Version popPseudoLocalityTag(int8_t locality, Version upTo) = 0;
+	// Returns the actual version to be popped from the log router tag for the given pseudo tag.
+	// For instance, a pseudo tag (-8, 2) means the actual popping tag is (-2, 2). Assuming there
+	// are multiple pseudo tags, the returned version is the min(all pseudo tags' "upTo" versions).
+	virtual Version popPseudoLocalityTag(Tag tag, Version upTo) = 0;
+
+	virtual void setBackupWorkers(const std::vector<InitializeBackupReply>& replies) = 0;
+
+	// Removes a finished backup worker from log system and returns true. Returns false
+	// if the worker is not found.
+	virtual bool removeBackupWorker(const BackupWorkerDoneRequest& req) = 0;
+
+	virtual LogEpoch getOldestBackupEpoch() const = 0;
 };
 
 struct LengthPrefixedStringRef {

fdbserver/LogSystemConfig.h

@@ -22,6 +22,7 @@
 #define FDBSERVER_LOGSYSTEMCONFIG_H
 #pragma once
 
+#include "fdbserver/BackupInterface.h"
 #include "fdbserver/TLogInterface.h"
 #include "fdbrpc/ReplicationPolicy.h"
 #include "fdbclient/DatabaseConfiguration.h"
@@ -82,6 +83,7 @@ struct TLogSet {
 	constexpr static FileIdentifier file_identifier = 6302317;
 	std::vector<OptionalInterface<TLogInterface>> tLogs;
 	std::vector<OptionalInterface<TLogInterface>> logRouters;
+	std::vector<OptionalInterface<BackupInterface>> backupWorkers;
 	int32_t tLogWriteAntiQuorum, tLogReplicationFactor;
 	std::vector< LocalityData > tLogLocalities; // Stores the localities of the log servers
 	TLogVersion tLogVersion;
@@ -95,12 +97,16 @@ struct TLogSet {
 	explicit TLogSet(const LogSet& rhs);
 
 	std::string toString() const {
-		return format("anti: %d replication: %d local: %d routers: %d tLogs: %s locality: %d", tLogWriteAntiQuorum, tLogReplicationFactor, isLocal, logRouters.size(), describe(tLogs).c_str(), locality);
+		return format("anti: %d replication: %d local: %d routers: %d tLogs: %s backupWorkers: %s locality: %d",
+		              tLogWriteAntiQuorum, tLogReplicationFactor, isLocal, logRouters.size(), describe(tLogs).c_str(),
+		              describe(backupWorkers).c_str(), locality);
 	}
 
 	bool operator == ( const TLogSet& rhs ) const {
-		if (tLogWriteAntiQuorum != rhs.tLogWriteAntiQuorum || tLogReplicationFactor != rhs.tLogReplicationFactor || isLocal != rhs.isLocal || satelliteTagLocations != rhs.satelliteTagLocations ||
-			startVersion != rhs.startVersion || tLogs.size() != rhs.tLogs.size() || locality != rhs.locality || logRouters.size() != rhs.logRouters.size()) {
+		if (tLogWriteAntiQuorum != rhs.tLogWriteAntiQuorum || tLogReplicationFactor != rhs.tLogReplicationFactor ||
+		    isLocal != rhs.isLocal || satelliteTagLocations != rhs.satelliteTagLocations ||
+		    startVersion != rhs.startVersion || tLogs.size() != rhs.tLogs.size() || locality != rhs.locality ||
+		    logRouters.size() != rhs.logRouters.size() || backupWorkers.size() != rhs.backupWorkers.size()) {
 			return false;
 		}
 		if ((tLogPolicy && !rhs.tLogPolicy) || (!tLogPolicy && rhs.tLogPolicy) || (tLogPolicy && (tLogPolicy->info() != rhs.tLogPolicy->info()))) {
@@ -116,6 +122,14 @@ struct TLogSet {
 				return false;
 			}
 		}
+		for (int j = 0; j < backupWorkers.size(); j++) {
+			if (backupWorkers[j].id() != rhs.backupWorkers[j].id() ||
+			    backupWorkers[j].present() != rhs.backupWorkers[j].present() ||
+			    (backupWorkers[j].present() &&
+			     backupWorkers[j].interf().getToken() != rhs.backupWorkers[j].interf().getToken())) {
+				return false;
+			}
+		}
 		return true;
 	}
 
@@ -137,38 +151,31 @@ struct TLogSet {
 
 	template <class Ar>
 	void serialize( Ar& ar ) {
-		if constexpr (is_fb_function<Ar>) {
-			serializer(ar, tLogs, logRouters, tLogWriteAntiQuorum, tLogReplicationFactor, tLogPolicy, tLogLocalities,
-			           isLocal, locality, startVersion, satelliteTagLocations, tLogVersion);
-		} else {
-			serializer(ar, tLogs, logRouters, tLogWriteAntiQuorum, tLogReplicationFactor, tLogPolicy, tLogLocalities, isLocal, locality, startVersion, satelliteTagLocations);
-			if (ar.isDeserializing && !ar.protocolVersion().hasTLogVersion()) {
-				tLogVersion = TLogVersion::V2;
-			} else {
-				serializer(ar, tLogVersion);
-			}
-			ASSERT(tLogPolicy.getPtr() == nullptr || tLogVersion != TLogVersion::UNSET);
-		}
+		serializer(ar, tLogs, logRouters, tLogWriteAntiQuorum, tLogReplicationFactor, tLogPolicy, tLogLocalities,
+		           isLocal, locality, startVersion, satelliteTagLocations, tLogVersion, backupWorkers);
 	}
 };
 
 struct OldTLogConf {
 	constexpr static FileIdentifier file_identifier = 16233772;
 	std::vector<TLogSet> tLogs;
-	Version epochEnd;
+	Version epochBegin, epochEnd;
 	int32_t logRouterTags;
 	int32_t txsTags;
 	std::set<int8_t> pseudoLocalities; // Tracking pseudo localities, e.g., tagLocalityLogRouterMapped, used in the old epoch.
+	LogEpoch epoch;
 
-	OldTLogConf() : epochEnd(0), logRouterTags(0), txsTags(0) {}
+	OldTLogConf() : epochBegin(0), epochEnd(0), logRouterTags(0), txsTags(0), epoch(0) {}
 	explicit OldTLogConf(const OldLogData&);
 
 	std::string toString() const {
 		return format("end: %d tags: %d %s", epochEnd, logRouterTags, describe(tLogs).c_str());
 	}
 
-	bool operator == ( const OldTLogConf& rhs ) const {
-		return tLogs == rhs.tLogs && epochEnd == rhs.epochEnd && logRouterTags == rhs.logRouterTags && txsTags == rhs.txsTags && pseudoLocalities == rhs.pseudoLocalities;
+	bool operator==(const OldTLogConf& rhs) const {
+		return tLogs == rhs.tLogs && epochBegin == rhs.epochBegin && epochEnd == rhs.epochEnd &&
+		       logRouterTags == rhs.logRouterTags && txsTags == rhs.txsTags &&
+		       pseudoLocalities == rhs.pseudoLocalities && epoch == rhs.epoch;
 	}
 
 	bool isEqualIds(OldTLogConf const& r) const {
@@ -185,7 +192,7 @@ struct OldTLogConf {
 
 	template <class Ar>
 	void serialize( Ar& ar ) {
-		serializer(ar, tLogs, epochEnd, logRouterTags, pseudoLocalities, txsTags);
+		serializer(ar, tLogs, epochBegin, epochEnd, logRouterTags, pseudoLocalities, txsTags, epoch);
 	}
 };
 
@@ -210,8 +217,12 @@ struct LogSystemConfig {
 	bool stopped;
 	Optional<Version> recoveredAt;
 	std::set<int8_t> pseudoLocalities;
+	LogEpoch epoch;
+	LogEpoch oldestBackupEpoch;
 
-	LogSystemConfig() : logSystemType(LogSystemType::empty), logRouterTags(0), txsTags(0), expectedLogSets(0), stopped(false) {}
+	LogSystemConfig(LogEpoch e = 0)
+	  : logSystemType(LogSystemType::empty), logRouterTags(0), txsTags(0), expectedLogSets(0), stopped(false), epoch(e),
+	    oldestBackupEpoch(e) {}
 
 	std::string toString() const {
 		return format("type: %d oldGenerations: %d tags: %d %s", logSystemType, oldTLogs.size(), logRouterTags, describe(tLogs).c_str());
@@ -349,7 +360,10 @@ struct LogSystemConfig {
 	bool operator == ( const LogSystemConfig& rhs ) const { return isEqual(rhs); }
 
 	bool isEqual(LogSystemConfig const& r) const {
-		return logSystemType == r.logSystemType && tLogs == r.tLogs && oldTLogs == r.oldTLogs && expectedLogSets == r.expectedLogSets && logRouterTags == r.logRouterTags && txsTags == r.txsTags && recruitmentID == r.recruitmentID && stopped == r.stopped && recoveredAt == r.recoveredAt && pseudoLocalities == r.pseudoLocalities;
+		return logSystemType == r.logSystemType && tLogs == r.tLogs && oldTLogs == r.oldTLogs &&
+		       expectedLogSets == r.expectedLogSets && logRouterTags == r.logRouterTags && txsTags == r.txsTags &&
+		       recruitmentID == r.recruitmentID && stopped == r.stopped && recoveredAt == r.recoveredAt &&
+		       pseudoLocalities == r.pseudoLocalities && epoch == r.epoch && oldestBackupEpoch == r.oldestBackupEpoch;
 	}
 
 	bool isEqualIds(LogSystemConfig const& r) const {
@@ -378,9 +392,67 @@ struct LogSystemConfig {
 		return false;
 	}
 
+	bool hasTLog(UID tid) const {
+		for (const auto& log : tLogs) {
+			if (std::count(log.tLogs.begin(), log.tLogs.end(), tid) > 0) {
+				return true;
+			}
+		}
+		for (const auto& old : oldTLogs) {
+			for (const auto& log : old.tLogs) {
+				if (std::count(log.tLogs.begin(), log.tLogs.end(), tid) > 0) {
+					return true;
+				}
+			}
+		}
+		return false;
+	}
+
+	bool hasLogRouter(UID rid) const {
+		for (const auto& log : tLogs) {
+			if (std::count(log.logRouters.begin(), log.logRouters.end(), rid) > 0) {
+				return true;
+			}
+		}
+		for (const auto& old : oldTLogs) {
+			for (const auto& log : old.tLogs) {
+				if (std::count(log.logRouters.begin(), log.logRouters.end(), rid) > 0) {
+					return true;
+				}
+			}
+		}
+		return false;
+	}
+
+	bool hasBackupWorker(UID bid) const {
+		for (const auto& log : tLogs) {
+			if (std::count(log.backupWorkers.begin(), log.backupWorkers.end(), bid) > 0) {
+				return true;
+			}
+		}
+		for (const auto& old : oldTLogs) {
+			for (const auto& log : old.tLogs) {
+				if (std::count(log.backupWorkers.begin(), log.backupWorkers.end(), bid) > 0) {
+					return true;
+				}
+			}
+		}
+		return false;
+	}
+
+	Version getEpochEndVersion(LogEpoch epoch) const {
+		for (const auto& old : oldTLogs) {
+			if (old.epoch == epoch) {
+				return old.epochEnd;
+			}
+		}
+		return invalidVersion;
+	}
+
 	template <class Ar>
-	void serialize( Ar& ar ) {
-		serializer(ar, logSystemType, tLogs, logRouterTags, oldTLogs, expectedLogSets, recruitmentID, stopped, recoveredAt, pseudoLocalities, txsTags);
+	void serialize(Ar& ar) {
+		serializer(ar, logSystemType, tLogs, logRouterTags, oldTLogs, expectedLogSets, recruitmentID, stopped,
+		           recoveredAt, pseudoLocalities, txsTags, epoch, oldestBackupEpoch);
 	}
 };
 

fdbserver/MasterInterface.h

@@ -37,6 +37,7 @@ struct MasterInterface {
 	RequestStream< struct TLogRejoinRequest > tlogRejoin; // sent by tlog (whether or not rebooted) to communicate with a new master
 	RequestStream< struct ChangeCoordinatorsRequest > changeCoordinators;
 	RequestStream< struct GetCommitVersionRequest > getCommitVersion;
+	RequestStream<struct BackupWorkerDoneRequest> notifyBackupWorkerDone;
 
 	NetworkAddress address() const { return changeCoordinators.getEndpoint().getPrimaryAddress(); }
 
@@ -44,9 +45,9 @@ struct MasterInterface {
 	template <class Archive>
 	void serialize(Archive& ar) {
 		if constexpr (!is_fb_function<Archive>) {
-                ASSERT( ar.protocolVersion().isValid() );
-        }
-		serializer(ar, locality, waitFailure, tlogRejoin, changeCoordinators, getCommitVersion);
+			ASSERT(ar.protocolVersion().isValid());
+		}
+		serializer(ar, locality, waitFailure, tlogRejoin, changeCoordinators, getCommitVersion, notifyBackupWorkerDone);
 	}
 
 	void initEndpoints() {
@@ -157,6 +158,21 @@ struct GetCommitVersionRequest {
 	}
 };
 
+struct BackupWorkerDoneRequest {
+	constexpr static FileIdentifier file_identifier = 8736351;
+	UID workerUID;
+	LogEpoch backupEpoch;
+	ReplyPromise<Void> reply;
+
+	BackupWorkerDoneRequest() : workerUID(), backupEpoch(-1) {}
+	BackupWorkerDoneRequest(UID id, LogEpoch epoch) : workerUID(id), backupEpoch(epoch) {}
+
+	template <class Ar>
+	void serialize(Ar& ar) {
+		serializer(ar, workerUID, backupEpoch, reply);
+	}
+};
+
 struct LifetimeToken {
 	UID ccID;
 	int64_t count;

fdbserver/MasterProxyServer.actor.cpp

@@ -487,7 +487,7 @@ bool isWhitelisted(const vector<Standalone<StringRef>>& binPathVec, StringRef bi
 }
 
 ACTOR Future<Void> addBackupMutations(ProxyCommitData* self, std::map<Key, MutationListRef>* logRangeMutations,
-                         LogPushData* toCommit, Version commitVersion) {
+                                      LogPushData* toCommit, Version commitVersion) {
 	state std::map<Key, MutationListRef>::iterator logRangeMutation = logRangeMutations->begin();
 	state int32_t version = commitVersion / CLIENT_KNOBS->LOG_RANGE_BLOCK_SIZE;
 	state int yieldBytes = 0;
@@ -1174,14 +1174,23 @@ struct TransactionRateInfo {
 	}
 };
 
-ACTOR Future<Void> sendGrvReplies(Future<GetReadVersionReply> replyFuture, std::vector<GetReadVersionRequest> requests, ProxyStats *stats) {
+ACTOR Future<Void> sendGrvReplies(Future<GetReadVersionReply> replyFuture, std::vector<GetReadVersionRequest> requests,
+                                  ProxyStats* stats, Version minKnownCommittedVersion) {
 	GetReadVersionReply reply = wait(replyFuture);
+
 	double end = timer();
 	for(GetReadVersionRequest const& request : requests) {
 		if(request.priority() >= GetReadVersionRequest::PRIORITY_DEFAULT) {
 			stats->grvLatencyBands.addMeasurement(end - request.requestTime());
 		}
-		request.reply.send(reply);
+		if (request.flags & GetReadVersionRequest::FLAG_USE_MIN_KNOWN_COMMITTED_VERSION) {
+			// Only backup worker may infrequently use this flag.
+			GetReadVersionReply minKCVReply = reply;
+			minKCVReply.version = minKnownCommittedVersion;
+			request.reply.send(minKCVReply);
+		} else {
+			request.reply.send(reply);
+		}
 	}
 
 	return Void();
@@ -1299,7 +1308,8 @@ ACTOR static Future<Void> transactionStarter(
 		for (int i = 0; i < start.size(); i++) {
 			if (start[i].size()) {
 				Future<GetReadVersionReply> readVersionReply = getLiveCommittedVersion(commitData, i, &otherProxies, debugID, transactionsStarted[i], systemTransactionsStarted[i], defaultPriTransactionsStarted[i], batchPriTransactionsStarted[i]);
-				addActor.send(sendGrvReplies(readVersionReply, start[i], &commitData->stats));
+				addActor.send(sendGrvReplies(readVersionReply, start[i], &commitData->stats,
+				                             commitData->minKnownCommittedVersion));
 
 				// for now, base dynamic batching on the time for normal requests (not read_risky)
 				if (i == 0) { 

fdbserver/OldTLogServer_4_6.actor.cpp

@@ -1087,28 +1087,9 @@ namespace oldTLog_4_6 {
 		loop {
 			auto const& inf = self->dbInfo->get();
 			bool isDisplaced = !std::count( inf.priorCommittedLogServers.begin(), inf.priorCommittedLogServers.end(), tli.id() );
-			isDisplaced = isDisplaced && inf.recoveryCount >= recoveryCount && inf.recoveryState != RecoveryState::UNINITIALIZED;
-
-			if(isDisplaced) {
-				for(auto& log : inf.logSystemConfig.tLogs) {
-					 if( std::count( log.tLogs.begin(), log.tLogs.end(), tli.id() ) ) {
-						isDisplaced = false;
-						break;
-					 }
-				}
-			}
-			if(isDisplaced) {
-				for(auto& old : inf.logSystemConfig.oldTLogs) {
-					for(auto& log : old.tLogs) {
-						 if( std::count( log.tLogs.begin(), log.tLogs.end(), tli.id() ) ) {
-							isDisplaced = false;
-							break;
-						 }
-					}
-				}
-			}
-			if ( isDisplaced )
-			{
+			isDisplaced = isDisplaced && inf.recoveryCount >= recoveryCount &&
+			              inf.recoveryState != RecoveryState::UNINITIALIZED && !inf.logSystemConfig.hasTLog(tli.id());
+			if (isDisplaced) {
 				TraceEvent("TLogDisplaced", tli.id()).detail("Reason", "DBInfoDoesNotContain").detail("RecoveryCount", recoveryCount).detail("InfRecoveryCount", inf.recoveryCount).detail("RecoveryState", (int)inf.recoveryState)
 					.detail("LogSysConf", describe(inf.logSystemConfig.tLogs)).detail("PriorLogs", describe(inf.priorCommittedLogServers)).detail("OldLogGens", inf.logSystemConfig.oldTLogs.size());
 				if (BUGGIFY) wait( delay( SERVER_KNOBS->BUGGIFY_WORKER_REMOVED_MAX_LAG * deterministicRandom()->random01() ) );

fdbserver/OldTLogServer_6_0.actor.cpp

@@ -695,9 +695,14 @@ ACTOR Future<Void> tLogPopCore( TLogData* self, Tag inputTag, Version to, Refere
 	}
 	state Version upTo = to;
 	int8_t tagLocality = inputTag.locality;
-	if (logData->logSystem->get().isValid() && logData->logSystem->get()->isPseudoLocality(tagLocality)) {
-		upTo = logData->logSystem->get()->popPseudoLocalityTag(tagLocality, to);
-		tagLocality = tagLocalityLogRouter;
+	if (isPseudoLocality(tagLocality)) {
+		if (logData->logSystem->get().isValid()) {
+			upTo = logData->logSystem->get()->popPseudoLocalityTag(inputTag, to);
+			tagLocality = tagLocalityLogRouter;
+		} else {
+			TraceEvent(SevWarn, "TLogPopNoLogSystem", self->dbgid).detail("Locality", tagLocality).detail("Version", upTo);
+			return Void();
+		}
 	}
 	state Tag tag(tagLocality, inputTag.id);
 	auto tagData = logData->getTagData(tag);
@@ -912,7 +917,7 @@ void commitMessages( TLogData* self, Reference<LogData> logData, Version version
 
 	for(auto& msg : taggedMessages) {
 		if(msg.message.size() > block.capacity() - block.size()) {
-			logData->messageBlocks.push_back( std::make_pair(version, block) );
+			logData->messageBlocks.emplace_back(version, block);
 			addedBytes += int64_t(block.size()) * SERVER_KNOBS->TLOG_MESSAGE_BLOCK_OVERHEAD_FACTOR;
 			block = Standalone<VectorRef<uint8_t>>();
 			block.reserve(block.arena(), std::max<int64_t>(SERVER_KNOBS->TLOG_MESSAGE_BLOCK_BYTES, msgSize));
@@ -947,7 +952,7 @@ void commitMessages( TLogData* self, Reference<LogData> logData, Version version
 			}
 
 			if (version >= tagData->popped) {
-				tagData->versionMessages.push_back(std::make_pair(version, LengthPrefixedStringRef((uint32_t*)(block.end() - msg.message.size()))));
+				tagData->versionMessages.emplace_back(version, LengthPrefixedStringRef((uint32_t*)(block.end() - msg.message.size())));
 				if(tagData->versionMessages.back().second.expectedSize() > SERVER_KNOBS->MAX_MESSAGE_SIZE) {
 					TraceEvent(SevWarnAlways, "LargeMessage").detail("Size", tagData->versionMessages.back().second.expectedSize());
 				}
@@ -967,7 +972,7 @@ void commitMessages( TLogData* self, Reference<LogData> logData, Version version
 
 		msgSize -= msg.message.size();
 	}
-	logData->messageBlocks.push_back( std::make_pair(version, block) );
+	logData->messageBlocks.emplace_back(version, block);
 	addedBytes += int64_t(block.size()) * SERVER_KNOBS->TLOG_MESSAGE_BLOCK_OVERHEAD_FACTOR;
 	addedBytes += overheadBytes;
 
@@ -1459,28 +1464,16 @@ ACTOR Future<Void> rejoinMasters( TLogData* self, TLogInterface tli, DBRecoveryC
 		} else {
 			isDisplaced = isDisplaced && ( ( inf.recoveryCount > recoveryCount && inf.recoveryState != RecoveryState::UNINITIALIZED ) || ( inf.recoveryCount == recoveryCount && inf.recoveryState == RecoveryState::FULLY_RECOVERED ) );
 		}
-		if(isDisplaced) {
-			for(auto& log : inf.logSystemConfig.tLogs) {
-				 if( std::count( log.tLogs.begin(), log.tLogs.end(), tli.id() ) ) {
-					isDisplaced = false;
-					break;
-				 }
-			}
-		}
-		if(isDisplaced) {
-			for(auto& old : inf.logSystemConfig.oldTLogs) {
-				for(auto& log : old.tLogs) {
-					 if( std::count( log.tLogs.begin(), log.tLogs.end(), tli.id() ) ) {
-						isDisplaced = false;
-						break;
-					 }
-				}
-			}
-		}
-		if ( isDisplaced )
-		{
-			TraceEvent("TLogDisplaced", tli.id()).detail("Reason", "DBInfoDoesNotContain").detail("RecoveryCount", recoveryCount).detail("InfRecoveryCount", inf.recoveryCount).detail("RecoveryState", (int)inf.recoveryState)
-				.detail("LogSysConf", describe(inf.logSystemConfig.tLogs)).detail("PriorLogs", describe(inf.priorCommittedLogServers)).detail("OldLogGens", inf.logSystemConfig.oldTLogs.size());
+		isDisplaced = isDisplaced && !inf.logSystemConfig.hasTLog(tli.id());
+		if (isDisplaced) {
+			TraceEvent("TLogDisplaced", tli.id())
+			    .detail("Reason", "DBInfoDoesNotContain")
+			    .detail("RecoveryCount", recoveryCount)
+			    .detail("InfRecoveryCount", inf.recoveryCount)
+			    .detail("RecoveryState", (int)inf.recoveryState)
+			    .detail("LogSysConf", describe(inf.logSystemConfig.tLogs))
+			    .detail("PriorLogs", describe(inf.priorCommittedLogServers))
+			    .detail("OldLogGens", inf.logSystemConfig.oldTLogs.size());
 			if (BUGGIFY) wait( delay( SERVER_KNOBS->BUGGIFY_WORKER_REMOVED_MAX_LAG * deterministicRandom()->random01() ) );
 			throw worker_removed();
 		}
@@ -1856,7 +1849,7 @@ ACTOR Future<Void> pullAsyncData( TLogData* self, Reference<LogData> logData, st
 				}
 			}
 
-			messages.push_back( TagsAndMessage(r->getMessageWithTags(), r->getTags()) );
+			messages.emplace_back(r->getMessageWithTags(), r->getTags());
 			r->nextMessage();
 		}
 

fdbserver/OldTLogServer_6_2.actor.cpp

@@ -1121,7 +1121,7 @@ void commitMessages( TLogData* self, Reference<LogData> logData, Version version
 
 	for(auto& msg : taggedMessages) {
 		if(msg.message.size() > block.capacity() - block.size()) {
-			logData->messageBlocks.push_back( std::make_pair(version, block) );
+			logData->messageBlocks.emplace_back(version, block);
 			addedBytes += int64_t(block.size()) * SERVER_KNOBS->TLOG_MESSAGE_BLOCK_OVERHEAD_FACTOR;
 			block = Standalone<VectorRef<uint8_t>>();
 			block.reserve(block.arena(), std::max<int64_t>(SERVER_KNOBS->TLOG_MESSAGE_BLOCK_BYTES, msgSize));
@@ -1156,7 +1156,7 @@ void commitMessages( TLogData* self, Reference<LogData> logData, Version version
 			}
 
 			if (version >= tagData->popped) {
-				tagData->versionMessages.push_back(std::make_pair(version, LengthPrefixedStringRef((uint32_t*)(block.end() - msg.message.size()))));
+				tagData->versionMessages.emplace_back(version, LengthPrefixedStringRef((uint32_t*)(block.end() - msg.message.size())));
 				if(tagData->versionMessages.back().second.expectedSize() > SERVER_KNOBS->MAX_MESSAGE_SIZE) {
 					TraceEvent(SevWarnAlways, "LargeMessage").detail("Size", tagData->versionMessages.back().second.expectedSize());
 				}
@@ -1176,7 +1176,7 @@ void commitMessages( TLogData* self, Reference<LogData> logData, Version version
 
 		msgSize -= msg.message.size();
 	}
-	logData->messageBlocks.push_back( std::make_pair(version, block) );
+	logData->messageBlocks.emplace_back(version, block);
 	addedBytes += int64_t(block.size()) * SERVER_KNOBS->TLOG_MESSAGE_BLOCK_OVERHEAD_FACTOR;
 	addedBytes += overheadBytes;
 
@@ -1236,9 +1236,14 @@ ACTOR Future<Void> tLogPopCore( TLogData* self, Tag inputTag, Version to, Refere
 	}
 	state Version upTo = to;
 	int8_t tagLocality = inputTag.locality;
-	if (logData->logSystem->get().isValid() && logData->logSystem->get()->isPseudoLocality(tagLocality)) {
-		upTo = logData->logSystem->get()->popPseudoLocalityTag(tagLocality, to);
-		tagLocality = tagLocalityLogRouter;
+	if (isPseudoLocality(tagLocality)) {
+		if (logData->logSystem->get().isValid()) {
+			upTo = logData->logSystem->get()->popPseudoLocalityTag(inputTag, to);
+			tagLocality = tagLocalityLogRouter;
+		} else {
+			TraceEvent(SevWarn, "TLogPopNoLogSystem", self->dbgid).detail("Locality", tagLocality).detail("Version", upTo);
+			return Void();
+		}
 	}
 	state Tag tag(tagLocality, inputTag.id);
 	auto tagData = logData->getTagData(tag);
@@ -1516,7 +1521,7 @@ ACTOR Future<Void> tLogPeekMessages( TLogData* self, TLogPeekRequest req, Refere
 					if (sd.version >= req.begin) {
 						firstVersion = std::min(firstVersion, sd.version);
 						const IDiskQueue::location end = sd.start.lo + sd.length;
-						commitLocations.push_back( std::make_pair(sd.start, end) );
+						commitLocations.emplace_back(sd.start, end);
 						// This isn't perfect, because we aren't accounting for page boundaries, but should be
 						// close enough.
 						commitBytes += sd.length;
@@ -1850,28 +1855,16 @@ ACTOR Future<Void> rejoinMasters( TLogData* self, TLogInterface tli, DBRecoveryC
 		} else {
 			isDisplaced = isDisplaced && ( ( inf.recoveryCount > recoveryCount && inf.recoveryState != RecoveryState::UNINITIALIZED ) || ( inf.recoveryCount == recoveryCount && inf.recoveryState == RecoveryState::FULLY_RECOVERED ) );
 		}
-		if(isDisplaced) {
-			for(auto& log : inf.logSystemConfig.tLogs) {
-				 if( std::count( log.tLogs.begin(), log.tLogs.end(), tli.id() ) ) {
-					isDisplaced = false;
-					break;
-				 }
-			}
-		}
-		if(isDisplaced) {
-			for(auto& old : inf.logSystemConfig.oldTLogs) {
-				for(auto& log : old.tLogs) {
-					 if( std::count( log.tLogs.begin(), log.tLogs.end(), tli.id() ) ) {
-						isDisplaced = false;
-						break;
-					 }
-				}
-			}
-		}
-		if ( isDisplaced )
-		{
-			TraceEvent("TLogDisplaced", tli.id()).detail("Reason", "DBInfoDoesNotContain").detail("RecoveryCount", recoveryCount).detail("InfRecoveryCount", inf.recoveryCount).detail("RecoveryState", (int)inf.recoveryState)
-				.detail("LogSysConf", describe(inf.logSystemConfig.tLogs)).detail("PriorLogs", describe(inf.priorCommittedLogServers)).detail("OldLogGens", inf.logSystemConfig.oldTLogs.size());
+		isDisplaced = isDisplaced && !inf.logSystemConfig.hasTLog(tli.id());
+		if (isDisplaced) {
+			TraceEvent("TLogDisplaced", tli.id())
+			    .detail("Reason", "DBInfoDoesNotContain")
+			    .detail("RecoveryCount", recoveryCount)
+			    .detail("InfRecoveryCount", inf.recoveryCount)
+			    .detail("RecoveryState", (int)inf.recoveryState)
+			    .detail("LogSysConf", describe(inf.logSystemConfig.tLogs))
+			    .detail("PriorLogs", describe(inf.priorCommittedLogServers))
+			    .detail("OldLogGens", inf.logSystemConfig.oldTLogs.size());
 			if (BUGGIFY) wait( delay( SERVER_KNOBS->BUGGIFY_WORKER_REMOVED_MAX_LAG * deterministicRandom()->random01() ) );
 			throw worker_removed();
 		}
@@ -2258,7 +2251,7 @@ ACTOR Future<Void> pullAsyncData( TLogData* self, Reference<LogData> logData, st
 				}
 			}
 
-			messages.push_back( TagsAndMessage(r->getMessageWithTags(), r->getTags()) );
+			messages.emplace_back(r->getMessageWithTags(), r->getTags());
 			r->nextMessage();
 		}
 
@@ -2449,7 +2442,7 @@ ACTOR Future<Void> restorePersistentState( TLogData* self, LocalityData locality
 		logData->recoveryCount = BinaryReader::fromStringRef<DBRecoveryCount>( fRecoverCounts.get()[idx].value, Unversioned() );
 		logData->removed = rejoinMasters(self, recruited, logData->recoveryCount, registerWithMaster.getFuture(), false);
 		removed.push_back(errorOr(logData->removed));
-		logsByVersion.push_back(std::make_pair(ver, id1));
+		logsByVersion.emplace_back(ver, id1);
 
 		TraceEvent("TLogPersistentStateRestore", self->dbgid).detail("LogId", logData->logId).detail("Ver", ver);
 		// Restore popped keys.  Pop operations that took place after the last (committed) updatePersistentDataVersion might be lost, but

fdbserver/QuietDatabase.actor.cpp

@@ -577,12 +577,13 @@ ACTOR Future<Void> waitForQuietDatabase( Database cx, Reference<AsyncVar<ServerD
 				if(++numSuccesses == 3) {
 					TraceEvent(("QuietDatabase" + phase + "Done").c_str());
 					break;
+				} else {
+					wait(delay(2.0));
 				}
-				else
-					wait(delay( 2.0 ) );
 			}
 		} catch (Error& e) {
-			if( e.code() != error_code_actor_cancelled && e.code() != error_code_attribute_not_found && e.code() != error_code_timed_out)
+			if (e.code() != error_code_actor_cancelled && e.code() != error_code_attribute_not_found &&
+			    e.code() != error_code_timed_out)
 				TraceEvent(("QuietDatabase" + phase + "Error").c_str()).error(e);
 
 			//Client invalid operation occurs if we don't get back a message from one of the servers, often corrected by retrying

fdbserver/ServerDBInfo.h

@@ -42,7 +42,7 @@ struct ServerDBInfo {
 	Optional<DataDistributorInterface> distributor;  // The best guess of current data distributor.
 	MasterInterface master;        // The best guess as to the most recent master, which might still be recovering
 	Optional<RatekeeperInterface> ratekeeper;
-	vector<ResolverInterface> resolvers;
+	std::vector<ResolverInterface> resolvers;
 	DBRecoveryCount recoveryCount; // A recovery count from DBCoreState.  A successful master recovery increments it twice; unsuccessful recoveries may increment it once. Depending on where the current master is in its recovery process, this might not have been written by the current master.
 	RecoveryState recoveryState;
 	LifetimeToken masterLifetime;  // Used by masterserver to detect not being the currently chosen master
@@ -52,7 +52,7 @@ struct ServerDBInfo {
 	Optional<LatencyBandConfig> latencyBandConfig;
 	std::vector<std::pair<uint16_t,StorageServerInterface>> storageCaches;
 
-	explicit ServerDBInfo() : recoveryCount(0), recoveryState(RecoveryState::UNINITIALIZED) {}
+	explicit ServerDBInfo() : recoveryCount(0), recoveryState(RecoveryState::UNINITIALIZED), logSystemConfig(0) {}
 
 	bool operator == (ServerDBInfo const& r) const { return id == r.id; }
 	bool operator != (ServerDBInfo const& r) const { return id != r.id; }

fdbserver/TLogServer.actor.cpp

@@ -26,6 +26,7 @@
 #include "fdbclient/KeyRangeMap.h"
 #include "fdbclient/RunTransaction.actor.h"
 #include "fdbclient/SystemData.h"
+#include "fdbclient/FDBTypes.h"
 #include "fdbserver/WorkerInterface.actor.h"
 #include "fdbserver/TLogInterface.h"
 #include "fdbserver/Knobs.h"
@@ -983,9 +984,14 @@ ACTOR Future<Void> tLogPopCore( TLogData* self, Tag inputTag, Version to, Refere
 	}
 	state Version upTo = to;
 	int8_t tagLocality = inputTag.locality;
-	if (logData->logSystem->get().isValid() && logData->logSystem->get()->isPseudoLocality(tagLocality)) {
-		upTo = logData->logSystem->get()->popPseudoLocalityTag(tagLocality, to);
-		tagLocality = tagLocalityLogRouter;
+	if (isPseudoLocality(tagLocality)) {
+		if (logData->logSystem->get().isValid()) {
+			upTo = logData->logSystem->get()->popPseudoLocalityTag(inputTag, to);
+			tagLocality = tagLocalityLogRouter;
+		} else {
+			TraceEvent(SevWarn, "TLogPopNoLogSystem", self->dbgid).detail("Locality", tagLocality).detail("Version", upTo);
+			return Void();
+		}
 	}
 	state Tag tag(tagLocality, inputTag.id);
 	auto tagData = logData->getTagData(tag);
@@ -1006,7 +1012,7 @@ ACTOR Future<Void> tLogPopCore( TLogData* self, Tag inputTag, Version to, Refere
 
 		if (upTo > logData->persistentDataDurableVersion)
 			wait(tagData->eraseMessagesBefore(upTo, self, logData, TaskPriority::TLogPop));
-		//TraceEvent("TLogPop", self->dbgid).detail("Tag", tag.toString()).detail("To", upTo);
+		TraceEvent("TLogPop", logData->logId).detail("Tag", tag.toString()).detail("To", upTo);
 	}
 	return Void();
 }
@@ -1211,7 +1217,7 @@ void commitMessages( TLogData* self, Reference<LogData> logData, Version version
 
 	for(auto& msg : taggedMessages) {
 		if(msg.message.size() > block.capacity() - block.size()) {
-			logData->messageBlocks.push_back( std::make_pair(version, block) );
+			logData->messageBlocks.emplace_back(version, block);
 			addedBytes += int64_t(block.size()) * SERVER_KNOBS->TLOG_MESSAGE_BLOCK_OVERHEAD_FACTOR;
 			block = Standalone<VectorRef<uint8_t>>();
 			block.reserve(block.arena(), std::max<int64_t>(SERVER_KNOBS->TLOG_MESSAGE_BLOCK_BYTES, msgSize));
@@ -1246,7 +1252,7 @@ void commitMessages( TLogData* self, Reference<LogData> logData, Version version
 			}
 
 			if (version >= tagData->popped) {
-				tagData->versionMessages.push_back(std::make_pair(version, LengthPrefixedStringRef((uint32_t*)(block.end() - msg.message.size()))));
+				tagData->versionMessages.emplace_back(version, LengthPrefixedStringRef((uint32_t*)(block.end() - msg.message.size())));
 				if(tagData->versionMessages.back().second.expectedSize() > SERVER_KNOBS->MAX_MESSAGE_SIZE) {
 					TraceEvent(SevWarnAlways, "LargeMessage").detail("Size", tagData->versionMessages.back().second.expectedSize());
 				}
@@ -1266,7 +1272,7 @@ void commitMessages( TLogData* self, Reference<LogData> logData, Version version
 
 		msgSize -= msg.message.size();
 	}
-	logData->messageBlocks.push_back( std::make_pair(version, block) );
+	logData->messageBlocks.emplace_back(version, block);
 	addedBytes += int64_t(block.size()) * SERVER_KNOBS->TLOG_MESSAGE_BLOCK_OVERHEAD_FACTOR;
 	addedBytes += overheadBytes;
 
@@ -1535,7 +1541,7 @@ ACTOR Future<Void> tLogPeekMessages( TLogData* self, TLogPeekRequest req, Refere
 					if (sd.version >= req.begin) {
 						firstVersion = std::min(firstVersion, sd.version);
 						const IDiskQueue::location end = sd.start.lo + sd.length;
-						commitLocations.push_back( std::make_pair(sd.start, end) );
+						commitLocations.emplace_back(sd.start, end);
 						// This isn't perfect, because we aren't accounting for page boundaries, but should be
 						// close enough.
 						commitBytes += sd.length;
@@ -1871,28 +1877,16 @@ ACTOR Future<Void> rejoinMasters( TLogData* self, TLogInterface tli, DBRecoveryC
 		} else {
 			isDisplaced = isDisplaced && ( ( inf.recoveryCount > recoveryCount && inf.recoveryState != RecoveryState::UNINITIALIZED ) || ( inf.recoveryCount == recoveryCount && inf.recoveryState == RecoveryState::FULLY_RECOVERED ) );
 		}
-		if(isDisplaced) {
-			for(auto& log : inf.logSystemConfig.tLogs) {
-				 if( std::count( log.tLogs.begin(), log.tLogs.end(), tli.id() ) ) {
-					isDisplaced = false;
-					break;
-				 }
-			}
-		}
-		if(isDisplaced) {
-			for(auto& old : inf.logSystemConfig.oldTLogs) {
-				for(auto& log : old.tLogs) {
-					 if( std::count( log.tLogs.begin(), log.tLogs.end(), tli.id() ) ) {
-						isDisplaced = false;
-						break;
-					 }
-				}
-			}
-		}
-		if ( isDisplaced )
-		{
-			TraceEvent("TLogDisplaced", tli.id()).detail("Reason", "DBInfoDoesNotContain").detail("RecoveryCount", recoveryCount).detail("InfRecoveryCount", inf.recoveryCount).detail("RecoveryState", (int)inf.recoveryState)
-				.detail("LogSysConf", describe(inf.logSystemConfig.tLogs)).detail("PriorLogs", describe(inf.priorCommittedLogServers)).detail("OldLogGens", inf.logSystemConfig.oldTLogs.size());
+		isDisplaced = isDisplaced && !inf.logSystemConfig.hasTLog(tli.id());
+		if (isDisplaced) {
+			TraceEvent("TLogDisplaced", tli.id())
+			    .detail("Reason", "DBInfoDoesNotContain")
+			    .detail("RecoveryCount", recoveryCount)
+			    .detail("InfRecoveryCount", inf.recoveryCount)
+			    .detail("RecoveryState", (int)inf.recoveryState)
+			    .detail("LogSysConf", describe(inf.logSystemConfig.tLogs))
+			    .detail("PriorLogs", describe(inf.priorCommittedLogServers))
+			    .detail("OldLogGens", inf.logSystemConfig.oldTLogs.size());
 			if (BUGGIFY) wait( delay( SERVER_KNOBS->BUGGIFY_WORKER_REMOVED_MAX_LAG * deterministicRandom()->random01() ) );
 			throw worker_removed();
 		}
@@ -2152,9 +2146,7 @@ void removeLog( TLogData* self, Reference<LogData> logData ) {
 			self->popOrder.pop_front();
 	}
 
-	if(self->id_data.size()) {
-		return;
-	} else {
+	if (self->id_data.size() == 0) {
 		throw worker_removed();
 	}
 }
@@ -2278,7 +2270,7 @@ ACTOR Future<Void> pullAsyncData( TLogData* self, Reference<LogData> logData, st
 				}
 			}
 
-			messages.push_back( TagsAndMessage(r->getMessageWithTags(), r->getTags()) );
+			messages.emplace_back(r->getMessageWithTags(), r->getTags());
 			r->nextMessage();
 		}
 
@@ -2471,7 +2463,7 @@ ACTOR Future<Void> restorePersistentState( TLogData* self, LocalityData locality
 		logData->recoveryCount = BinaryReader::fromStringRef<DBRecoveryCount>( fRecoverCounts.get()[idx].value, Unversioned() );
 		logData->removed = rejoinMasters(self, recruited, logData->recoveryCount, registerWithMaster.getFuture(), false);
 		removed.push_back(errorOr(logData->removed));
-		logsByVersion.push_back(std::make_pair(ver, id1));
+		logsByVersion.emplace_back(ver, id1);
 
 		TraceEvent("TLogPersistentStateRestore", self->dbgid).detail("LogId", logData->logId).detail("Ver", ver);
 		// Restore popped keys.  Pop operations that took place after the last (committed) updatePersistentDataVersion might be lost, but
@@ -2605,27 +2597,25 @@ bool tlogTerminated( TLogData* self, IKeyValueStore* persistentData, TLogQueue*
 
 ACTOR Future<Void> updateLogSystem(TLogData* self, Reference<LogData> logData, LogSystemConfig recoverFrom, Reference<AsyncVar<Reference<ILogSystem>>> logSystem) {
 	loop {
-		bool found = false;
-		if(self->dbInfo->get().logSystemConfig.recruitmentID == logData->recruitmentID) {
-			if( self->dbInfo->get().logSystemConfig.isNextGenerationOf(recoverFrom) ) {
+		bool found = self->dbInfo->get().logSystemConfig.recruitmentID == logData->recruitmentID;
+		if (found) {
+			if (self->dbInfo->get().logSystemConfig.isNextGenerationOf(recoverFrom)) {
 				logSystem->set(ILogSystem::fromOldLogSystemConfig( logData->logId, self->dbInfo->get().myLocality, self->dbInfo->get().logSystemConfig ));
-				found = true;
-			} else if( self->dbInfo->get().logSystemConfig.isEqualIds(recoverFrom) ) {
+			} else if (self->dbInfo->get().logSystemConfig.isEqualIds(recoverFrom)) {
 				logSystem->set(ILogSystem::fromLogSystemConfig( logData->logId, self->dbInfo->get().myLocality, self->dbInfo->get().logSystemConfig, false, true ));
-				found = true;
-			}
-			else if( self->dbInfo->get().recoveryState >= RecoveryState::ACCEPTING_COMMITS ) {
+			} else if (self->dbInfo->get().recoveryState >= RecoveryState::ACCEPTING_COMMITS) {
 				logSystem->set(ILogSystem::fromLogSystemConfig( logData->logId, self->dbInfo->get().myLocality, self->dbInfo->get().logSystemConfig, true ));
-				found = true;
+			} else {
+				found = false;
 			}
 		}
-		if( !found ) {
+		if (!found) {
 			logSystem->set(Reference<ILogSystem>());
 		} else {
 			logData->logSystem->get()->pop(logData->logRouterPoppedVersion, logData->remoteTag, logData->durableKnownCommittedVersion, logData->locality);
 		}
 		TraceEvent("TLogUpdate", self->dbgid).detail("LogId", logData->logId).detail("RecruitmentID", logData->recruitmentID).detail("DbRecruitmentID", self->dbInfo->get().logSystemConfig.recruitmentID).detail("RecoverFrom", recoverFrom.toString()).detail("DbInfo", self->dbInfo->get().logSystemConfig.toString()).detail("Found", found).detail("LogSystem", (bool) logSystem->get() ).detail("RecoveryState", (int)self->dbInfo->get().recoveryState);
-		for(auto it : self->dbInfo->get().logSystemConfig.oldTLogs) {
+		for (const auto& it : self->dbInfo->get().logSystemConfig.oldTLogs) {
 			TraceEvent("TLogUpdateOld", self->dbgid).detail("LogId", logData->logId).detail("DbInfo", it.toString());
 		}
 		wait( self->dbInfo->onChange() );

fdbserver/TagPartitionedLogSystem.actor.cpp

@@ -45,17 +45,17 @@ struct OldLogData {
 	std::vector<Reference<LogSet>> tLogs;
 	int32_t logRouterTags;
 	int32_t txsTags; // The number of txsTags, which may change across generations.
-	Version epochEnd;
+	Version epochBegin, epochEnd;
 	std::set<int8_t> pseudoLocalities;
+	LogEpoch epoch;
 
-	OldLogData() : epochEnd(0), logRouterTags(0), txsTags(0) {}
+	OldLogData() : epochBegin(0), epochEnd(0), logRouterTags(0), txsTags(0), epoch(0) {}
 
 	// Constructor for T of OldTLogConf and OldTLogCoreData
-	template<class T>
+	template <class T>
 	explicit OldLogData(const T& conf)
-		: logRouterTags(conf.logRouterTags), txsTags(conf.txsTags), epochEnd(conf.epochEnd),
-		  pseudoLocalities(conf.pseudoLocalities)
-	{
+	  : logRouterTags(conf.logRouterTags), txsTags(conf.txsTags), epochBegin(conf.epochBegin), epochEnd(conf.epochEnd),
+	    pseudoLocalities(conf.pseudoLocalities), epoch(conf.epoch) {
 		tLogs.resize(conf.tLogs.size());
 		for (int j = 0; j < conf.tLogs.size(); j++) {
 			Reference<LogSet> logSet(new LogSet(conf.tLogs[j]));
@@ -81,12 +81,15 @@ LogSet::LogSet(const TLogSet& tLogSet) :
 	locality(tLogSet.locality), startVersion(tLogSet.startVersion),
 	satelliteTagLocations(tLogSet.satelliteTagLocations)
 {
-	for(const auto& log : tLogSet.tLogs) {
+	for (const auto& log : tLogSet.tLogs) {
 		logServers.emplace_back(new AsyncVar<OptionalInterface<TLogInterface>>(log));
 	}
-	for(const auto& log : tLogSet.logRouters) {
+	for (const auto& log : tLogSet.logRouters) {
 		logRouters.emplace_back(new AsyncVar<OptionalInterface<TLogInterface>>(log));
 	}
+	for (const auto& log : tLogSet.backupWorkers) {
+		backupWorkers.emplace_back(new AsyncVar<OptionalInterface<BackupInterface>>(log));
+	}
 	filterLocalityDataForPolicy(tLogPolicy, &tLogLocalities);
 	updateLocalitySet(tLogLocalities);
 }
@@ -99,9 +102,10 @@ LogSet::LogSet(const CoreTLogSet& coreSet) :
 	locality(coreSet.locality), startVersion(coreSet.startVersion),
 	satelliteTagLocations(coreSet.satelliteTagLocations)
 {
-	for(const auto& log : coreSet.tLogs) {
+	for (const auto& log : coreSet.tLogs) {
 		logServers.emplace_back(new AsyncVar<OptionalInterface<TLogInterface>>(OptionalInterface<TLogInterface>(log)));
 	}
+	// Do NOT recover coreSet.backupWorkers, because master will recruit new ones.
 	filterLocalityDataForPolicy(tLogPolicy, &tLogLocalities);
 	updateLocalitySet(tLogLocalities);
 }
@@ -117,16 +121,17 @@ TLogSet::TLogSet(const LogSet& rhs) :
 	for (const auto& tlog : rhs.logServers) {
 		tLogs.push_back(tlog->get());
 	}
-
 	for (const auto& logRouter : rhs.logRouters) {
 		logRouters.push_back(logRouter->get());
 	}
+	for (const auto& worker : rhs.backupWorkers) {
+		backupWorkers.push_back(worker->get());
+	}
 }
 
-OldTLogConf::OldTLogConf(const OldLogData& oldLogData) :
-	logRouterTags(oldLogData.logRouterTags), txsTags(oldLogData.txsTags), epochEnd(oldLogData.epochEnd),
-	pseudoLocalities(oldLogData.pseudoLocalities)
-{
+OldTLogConf::OldTLogConf(const OldLogData& oldLogData)
+  : logRouterTags(oldLogData.logRouterTags), txsTags(oldLogData.txsTags), epochBegin(oldLogData.epochBegin),
+    epochEnd(oldLogData.epochEnd), pseudoLocalities(oldLogData.pseudoLocalities), epoch(oldLogData.epoch) {
 	for (const Reference<LogSet>& logSet : oldLogData.tLogs) {
 		tLogs.emplace_back(*logSet);
 	}
@@ -144,12 +149,12 @@ CoreTLogSet::CoreTLogSet(const LogSet& logset) :
 	for (const auto &log : logset.logServers) {
 		tLogs.push_back(log->get().id());
 	}
+	// Do NOT store logset.backupWorkers, because master will recruit new ones.
 }
 
-OldTLogCoreData::OldTLogCoreData(const OldLogData& oldData) :
-	logRouterTags(oldData.logRouterTags), txsTags(oldData.txsTags), epochEnd(oldData.epochEnd),
-	pseudoLocalities(oldData.pseudoLocalities)
-{
+OldTLogCoreData::OldTLogCoreData(const OldLogData& oldData)
+  : logRouterTags(oldData.logRouterTags), txsTags(oldData.txsTags), epochBegin(oldData.epochBegin),
+    epochEnd(oldData.epochEnd), pseudoLocalities(oldData.pseudoLocalities), epoch(oldData.epoch) {
 	for (const Reference<LogSet>& logSet : oldData.tLogs) {
 		if (logSet->logServers.size()) {
 			tLogs.emplace_back(*logSet);
@@ -158,7 +163,7 @@ OldTLogCoreData::OldTLogCoreData(const OldLogData& oldData) :
 }
 
 struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogSystem> {
-	UID dbgid;
+	const UID dbgid;
 	LogSystemType logSystemType;
 	std::vector<Reference<LogSet>> tLogs;
 	int expectedLogSets;
@@ -168,9 +173,11 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 	int repopulateRegionAntiQuorum;
 	bool stopped;
 	std::set<int8_t> pseudoLocalities; // Represent special localities that will be mapped to tagLocalityLogRouter
-	std::map<int8_t, Version> pseudoLocalityPopVersion;
+	const LogEpoch epoch;
+	LogEpoch oldestBackupEpoch;
 
 	// new members
+	std::map<Tag, Version> pseudoLocalityPopVersion;
 	Future<Void> rejoins;
 	Future<Void> recoveryComplete;
 	Future<Void> remoteRecovery;
@@ -179,6 +186,7 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 	AsyncVar<bool> recoveryCompleteWrittenToCoreState;
 	bool remoteLogsWrittenToCoreState;
 	bool hasRemoteServers;
+	AsyncTrigger backupWorkerChanged;
 
 	Optional<Version> recoverAt;
 	Optional<Version> recoveredAt;
@@ -190,21 +198,24 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 	std::vector<OldLogData> oldLogData;
 	AsyncTrigger logSystemConfigChanged;
 
-	TagPartitionedLogSystem( UID dbgid, LocalityData locality, Optional<PromiseStream<Future<Void>>> addActor = Optional<PromiseStream<Future<Void>>>() ) : dbgid(dbgid), locality(locality), addActor(addActor), popActors(false), recoveryCompleteWrittenToCoreState(false), remoteLogsWrittenToCoreState(false), logSystemType(LogSystemType::empty), logRouterTags(0), txsTags(0), expectedLogSets(0), hasRemoteServers(false), stopped(false), repopulateRegionAntiQuorum(0) {}
+	TagPartitionedLogSystem(UID dbgid, LocalityData locality, LogEpoch e,
+	                        Optional<PromiseStream<Future<Void>>> addActor = Optional<PromiseStream<Future<Void>>>())
+	  : dbgid(dbgid), logSystemType(LogSystemType::empty), expectedLogSets(0), logRouterTags(0), txsTags(0),
+	    repopulateRegionAntiQuorum(0), epoch(e), oldestBackupEpoch(e), recoveryCompleteWrittenToCoreState(false),
+	    locality(locality), remoteLogsWrittenToCoreState(false), hasRemoteServers(false), stopped(false),
+	    addActor(addActor), popActors(false) {}
 
-	virtual void stopRejoins() {
-		rejoins = Future<Void>();
-	}
+	void stopRejoins() override { rejoins = Future<Void>(); }
 
-	virtual void addref() {
+	void addref() override {
 		ReferenceCounted<TagPartitionedLogSystem>::addref();
 	}
 
-	virtual void delref() {
+	void delref() override {
 		ReferenceCounted<TagPartitionedLogSystem>::delref();
 	}
 
-	virtual std::string describe() {
+	std::string describe() override {
 		std::string result;
 		for( int i = 0; i < tLogs.size(); i++ ) {
 			result += format("%d: ", i);
@@ -215,42 +226,50 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		return result;
 	}
 
-	virtual UID getDebugID() {
-		return dbgid;
-	}
+	UID getDebugID() override { return dbgid; }
 
 	void addPseudoLocality(int8_t locality) {
 		ASSERT(locality < 0);
 		pseudoLocalities.insert(locality);
-		pseudoLocalityPopVersion[locality] = 0;
+		for (uint16_t i = 0; i < logRouterTags; i++) {
+			pseudoLocalityPopVersion[Tag(locality, i)] = 0;
+		}
 	}
 
 	Tag getPseudoPopTag(Tag tag, ProcessClass::ClassType type) override {
 		switch (type) {
 		case ProcessClass::LogRouterClass:
-			if (tag.locality == tagLocalityLogRouter && pseudoLocalities.count(tag.locality) > 0) {
+			if (tag.locality == tagLocalityLogRouter) {
+				ASSERT(pseudoLocalities.count(tagLocalityLogRouterMapped) > 0);
 				tag.locality = tagLocalityLogRouterMapped;
 			}
 			break;
 
-		default:
+		case ProcessClass::BackupClass:
+			if (tag.locality == tagLocalityLogRouter) {
+				ASSERT(pseudoLocalities.count(tagLocalityBackup) > 0);
+				tag.locality = tagLocalityBackup;
+			}
+			break;
+
+		default: // This should be an error at caller site.
 			break;
 		}
 		return tag;
 	}
 
-	bool isPseudoLocality(int8_t locality) override {
-		return pseudoLocalities.count(locality) > 0;
-	}
+	bool hasPseudoLocality(int8_t locality) override { return pseudoLocalities.count(locality) > 0; }
 
-	Version popPseudoLocalityTag(int8_t locality, Version upTo) override {
-		ASSERT(isPseudoLocality(locality));
-		auto& localityVersion = pseudoLocalityPopVersion[locality];
+	Version popPseudoLocalityTag(Tag tag, Version upTo) override {
+		ASSERT(isPseudoLocality(tag.locality) && hasPseudoLocality(tag.locality));
+
+		Version& localityVersion = pseudoLocalityPopVersion[tag];
 		localityVersion = std::max(localityVersion, upTo);
 		Version minVersion = localityVersion;
-		for (const auto& it : pseudoLocalityPopVersion) {
-			minVersion = std::min(minVersion, it.second);
+		for (const int8_t locality : pseudoLocalities) {
+			minVersion = std::min(minVersion, pseudoLocalityPopVersion[Tag(locality, tag.id)]);
 		}
+		TraceEvent("Pop", dbgid).detail("Tag", tag.toString()).detail("Version", upTo).detail("PopVersion", minVersion);
 		return minVersion;
 	}
 
@@ -261,7 +280,8 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 	static Reference<ILogSystem> fromLogSystemConfig( UID const& dbgid, LocalityData const& locality, LogSystemConfig const& lsConf, bool excludeRemote, bool useRecoveredAt, Optional<PromiseStream<Future<Void>>> addActor ) {
 		ASSERT(lsConf.logSystemType == LogSystemType::tagPartitioned || (lsConf.logSystemType == LogSystemType::empty && !lsConf.tLogs.size()));
 		//ASSERT(lsConf.epoch == epoch);  //< FIXME
-		Reference<TagPartitionedLogSystem> logSystem( new TagPartitionedLogSystem(dbgid, locality, addActor) );
+		Reference<TagPartitionedLogSystem> logSystem(
+		    new TagPartitionedLogSystem(dbgid, locality, lsConf.epoch, addActor));
 
 		logSystem->tLogs.reserve(lsConf.tLogs.size());
 		logSystem->expectedLogSets = lsConf.expectedLogSets;
@@ -281,6 +301,9 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 
 		for (const auto& oldTlogConf : lsConf.oldTLogs) {
 			logSystem->oldLogData.emplace_back(oldTlogConf);
+			//TraceEvent("BWFromLSConf")
+			//    .detail("Epoch", logSystem->oldLogData.back().epoch)
+			//    .detail("Version", logSystem->oldLogData.back().epochEnd);
 		}
 
 		logSystem->logSystemType = lsConf.logSystemType;
@@ -290,7 +313,8 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 	static Reference<ILogSystem> fromOldLogSystemConfig( UID const& dbgid, LocalityData const& locality, LogSystemConfig const& lsConf ) {
 		ASSERT( lsConf.logSystemType == LogSystemType::tagPartitioned || (lsConf.logSystemType == LogSystemType::empty && !lsConf.tLogs.size()) );
 		//ASSERT(lsConf.epoch == epoch);  //< FIXME
-		Reference<TagPartitionedLogSystem> logSystem( new TagPartitionedLogSystem(dbgid, locality) );
+		const LogEpoch e = lsConf.oldTLogs.size() > 0 ? lsConf.oldTLogs[0].epoch : 0;
+		Reference<TagPartitionedLogSystem> logSystem(new TagPartitionedLogSystem(dbgid, locality, e));
 
 		if (lsConf.oldTLogs.size()) {
 			for (const TLogSet& tLogSet : lsConf.oldTLogs[0].tLogs) {
@@ -311,7 +335,7 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		return logSystem;
 	}
 
-	virtual void toCoreState( DBCoreState& newState ) {
+	void toCoreState(DBCoreState& newState) override {
 		if( recoveryComplete.isValid() && recoveryComplete.isError() )
 			throw recoveryComplete.getError();
 
@@ -336,17 +360,21 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		if(!recoveryComplete.isValid() || !recoveryComplete.isReady() || (repopulateRegionAntiQuorum == 0 && (!remoteRecoveryComplete.isValid() || !remoteRecoveryComplete.isReady()))) {
 			for (const auto& oldData : oldLogData) {
 				newState.oldTLogData.emplace_back(oldData);
+				TraceEvent("BWToCore")
+				    .detail("Epoch", newState.oldTLogData.back().epoch)
+				    .detail("BeginVersion", newState.oldTLogData.back().epochBegin)
+				    .detail("EndVersion", newState.oldTLogData.back().epochEnd);
 			}
 		}
 
 		newState.logSystemType = logSystemType;
 	}
 
-	virtual bool remoteStorageRecovered() {
+	bool remoteStorageRecovered() override {
 		return remoteRecoveryComplete.isValid() && remoteRecoveryComplete.isReady();
 	}
 
-	virtual Future<Void> onCoreStateChanged() {
+	Future<Void> onCoreStateChanged() override {
 		std::vector<Future<Void>> changes;
 		changes.push_back(Never());
 		if(recoveryComplete.isValid() && !recoveryComplete.isReady()) {
@@ -361,8 +389,8 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		return waitForAny(changes);
 	}
 
-	virtual void coreStateWritten( DBCoreState const& newState ) {
-		if( !newState.oldTLogData.size() ) {
+	void coreStateWritten(DBCoreState const& newState) override {
+		if (!newState.oldTLogData.size()) {
 			recoveryCompleteWrittenToCoreState.set(true);
 		}
 		for(auto& t : newState.tLogs) {
@@ -374,15 +402,16 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		}
 	}
 
-	virtual Future<Void> onError() {
+	Future<Void> onError() override {
 		return onError_internal(this);
 	}
 
 	ACTOR static Future<Void> onError_internal( TagPartitionedLogSystem* self ) {
 		// Never returns normally, but throws an error if the subsystem stops working
 		loop {
-			vector<Future<Void>> failed;
-			vector<Future<Void>> changes;
+			std::vector<Future<Void>> failed;
+			std::vector<Future<Void>> backupFailed(1, Never());
+			std::vector<Future<Void>> changes;
 
 			for(auto& it : self->tLogs) {
 				for(auto &t : it->logServers) {
@@ -399,6 +428,15 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 						changes.push_back(t->onChange());
 					}
 				}
+				for (const auto& worker : it->backupWorkers) {
+					if (worker->get().present()) {
+						backupFailed.push_back(waitFailureClient(
+						    worker->get().interf().waitFailure, SERVER_KNOBS->BACKUP_TIMEOUT,
+						    -SERVER_KNOBS->BACKUP_TIMEOUT / SERVER_KNOBS->SECONDS_BEFORE_NO_FAILURE_DELAY));
+					} else {
+						changes.push_back(worker->onChange());
+					}
+				}
 			}
 
 			if(!self->recoveryCompleteWrittenToCoreState.get()) {
@@ -412,6 +450,16 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 							}
 						}
 					}
+					// Monitor changes of backup workers for old epochs.
+					for (const auto& worker : old.tLogs[0]->backupWorkers) {
+						if (worker->get().present()) {
+							backupFailed.push_back(waitFailureClient(
+							    worker->get().interf().waitFailure, SERVER_KNOBS->BACKUP_TIMEOUT,
+							    -SERVER_KNOBS->BACKUP_TIMEOUT / SERVER_KNOBS->SECONDS_BEFORE_NO_FAILURE_DELAY));
+						} else {
+							changes.push_back(worker->onChange());
+						}
+					}
 				}
 			}
 
@@ -420,13 +468,16 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 			}
 
 			changes.push_back(self->recoveryCompleteWrittenToCoreState.onChange());
+			changes.push_back(self->backupWorkerChanged.onTrigger());
 
 			ASSERT( failed.size() >= 1 );
-			wait( quorum(changes, 1) || tagError<Void>( quorum( failed, 1 ), master_tlog_failed() ) );
+			wait(quorum(changes, 1) || tagError<Void>(quorum(failed, 1), master_tlog_failed()) ||
+			     tagError<Void>(quorum(backupFailed, 1), master_backup_worker_failed()));
 		}
 	}
 
-	virtual Future<Version> push( Version prevVersion, Version version, Version knownCommittedVersion, Version minKnownCommittedVersion, LogPushData& data, Optional<UID> debugID ) {
+	Future<Version> push(Version prevVersion, Version version, Version knownCommittedVersion,
+	                     Version minKnownCommittedVersion, LogPushData& data, Optional<UID> debugID) override {
 		// FIXME: Randomize request order as in LegacyLogSystem?
 		vector<Future<Void>> quorumResults;
 		vector<Future<TLogCommitReply>> allReplies;
@@ -483,8 +534,7 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 				TraceEvent("TLogPeekAllAddingCurrent", dbgid).detail("Tag", tag.toString()).detail("Begin", begin).detail("End", end).detail("BestLogs", localSets[bestSet]->logServerString());
 				cursors.emplace_back(new ILogSystem::SetPeekCursor( localSets, bestSet, localSets[bestSet]->bestLocationFor( tag ), tag, lastBegin, end, parallelGetMore));
 			}
-			int i = 0;
-			while(begin < lastBegin) {
+			for (int i = 0; begin < lastBegin; i++) {
 				if(i == oldLogData.size()) {
 					if(tag == txsTag || tag.locality == tagLocalityTxs || tag == cacheTag) {
 						break;
@@ -514,7 +564,6 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 				if(!localOldSets.size()) {
 					TraceEvent("TLogPeekAllNoLocalSets", dbgid).detail("Tag", tag.toString()).detail("Begin", begin).detail("End", end).detail("LastBegin", lastBegin);
 					if(!cursors.size() && !foundSpecial) {
-						i++;
 						continue;
 					}
 					return Reference<ILogSystem::ServerPeekCursor>( new ILogSystem::ServerPeekCursor( Reference<AsyncVar<OptionalInterface<TLogInterface>>>(), tag, begin, getPeekEnd(), false, false ) );
@@ -531,7 +580,6 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 					}
 					lastBegin = thisBegin;
 				}
-				i++;
 			}
 
 			return Reference<ILogSystem::MultiCursor>( new ILogSystem::MultiCursor(cursors, epochEnds) );
@@ -601,7 +649,7 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		}
 	}
 
-	virtual Reference<IPeekCursor> peek( UID dbgid, Version begin, Optional<Version> end, Tag tag, bool parallelGetMore ) {
+	Reference<IPeekCursor> peek( UID dbgid, Version begin, Optional<Version> end, Tag tag, bool parallelGetMore ) override {
 		if(!tLogs.size()) {
 			TraceEvent("TLogPeekNoLogSets", dbgid).detail("Tag", tag.toString()).detail("Begin", begin);
 			return Reference<ILogSystem::ServerPeekCursor>( new ILogSystem::ServerPeekCursor( Reference<AsyncVar<OptionalInterface<TLogInterface>>>(), tag, begin, getPeekEnd(), false, false ) );
@@ -614,7 +662,7 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		}
 	}
 
-	virtual Reference<IPeekCursor> peek( UID dbgid, Version begin, Optional<Version> end, std::vector<Tag> tags, bool parallelGetMore ) {
+	Reference<IPeekCursor> peek(UID dbgid, Version begin, Optional<Version> end, std::vector<Tag> tags, bool parallelGetMore) override {
 		if(tags.empty()) {
 			TraceEvent("TLogPeekNoTags", dbgid).detail("Begin", begin);
 			return Reference<ILogSystem::ServerPeekCursor>( new ILogSystem::ServerPeekCursor( Reference<AsyncVar<OptionalInterface<TLogInterface>>>(), invalidTag, begin, getPeekEnd(), false, false ) );
@@ -683,8 +731,7 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 				}
 			}
 			Version lastBegin = tLogs[bestSet]->startVersion;
-			int i = 0;
-			while(begin < lastBegin) {
+			for (int i = 0; begin < lastBegin; i++) {
 				if(i == oldLogData.size()) {
 					if((tag == txsTag || tag.locality == tagLocalityTxs) && cursors.size()) {
 						break;
@@ -718,7 +765,6 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 					if(oldLogData[i].logRouterTags == 0 || logCount > 1 || foundSpecial) {
 						throw worker_removed();
 					}
-					i++;
 					continue;
 				}
 
@@ -735,14 +781,13 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 					}
 					lastBegin = thisBegin;
 				}
-				i++;
 			}
 
 			return Reference<ILogSystem::MultiCursor>( new ILogSystem::MultiCursor(cursors, epochEnds) );
 		}
 	}
 
-	virtual Reference<IPeekCursor> peekTxs( UID dbgid, Version begin, int8_t peekLocality, Version localEnd, bool canDiscardPopped ) {
+	Reference<IPeekCursor> peekTxs(UID dbgid, Version begin, int8_t peekLocality, Version localEnd, bool canDiscardPopped) override {
 		Version end = getEnd();
 		if(!tLogs.size()) {
 			TraceEvent("TLogPeekTxsNoLogs", dbgid);
@@ -824,7 +869,7 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		}
 	}
 
-	virtual Reference<IPeekCursor> peekSingle( UID dbgid, Version begin, Tag tag, std::vector<std::pair<Version,Tag>> history ) {
+	Reference<IPeekCursor> peekSingle(UID dbgid, Version begin, Tag tag, std::vector<std::pair<Version,Tag>> history) override {
 		while(history.size() && begin >= history.back().first) {
 			history.pop_back();
 		}
@@ -849,15 +894,15 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		}
 	}
 
-	virtual Reference<IPeekCursor> peekLogRouter( UID dbgid, Version begin, Tag tag ) {
+	Reference<IPeekCursor> peekLogRouter(UID dbgid, Version begin, Tag tag) override {
 		bool found = false;
-		for( auto& log : tLogs ) {
-			found = log->hasLogRouter(dbgid);
-			if(found) {
+		for (const auto& log : tLogs) {
+			found = log->hasLogRouter(dbgid) || log->hasBackupWorker(dbgid);
+			if (found) {
 				break;
 			}
 		}
-		if( found ) {
+		if (found) {
 			if(stopped) {
 				std::vector<Reference<LogSet>> localSets;
 				int bestPrimarySet = 0;
@@ -909,11 +954,11 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 			}
 		}
 		bool firstOld = true;
-		for(auto& old : oldLogData) {
+		for (const auto& old : oldLogData) {
 			found = false;
-			for( auto& log : old.tLogs ) {
-				found = log->hasLogRouter(dbgid);
-				if(found) {
+			for (const auto& log : old.tLogs) {
+				found = log->hasLogRouter(dbgid) || log->hasBackupWorker(dbgid);
+				if (found) {
 					break;
 				}
 			}
@@ -948,7 +993,7 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		return Reference<ILogSystem::ServerPeekCursor>( new ILogSystem::ServerPeekCursor( Reference<AsyncVar<OptionalInterface<TLogInterface>>>(), tag, begin, getPeekEnd(), false, false ) );
 	}
 
-	virtual Version getKnownCommittedVersion() {
+	Version getKnownCommittedVersion() override {
 		Version result = invalidVersion;
 		for(auto& it : lockResults) {
 			auto versions = TagPartitionedLogSystem::getDurableVersion(dbgid, it);
@@ -959,7 +1004,7 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		return result;
 	}
 
-	virtual Future<Void> onKnownCommittedVersionChange() {
+	Future<Void> onKnownCommittedVersionChange() override {
 		std::vector<Future<Void>> result;
 		for(auto& it : lockResults) {
 			result.push_back(TagPartitionedLogSystem::getDurableVersionChanged(it));
@@ -1000,7 +1045,7 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		}
 	}
 
-	virtual void popTxs( Version upTo, int8_t popLocality ) {
+	void popTxs(Version upTo, int8_t popLocality) override {
 		if( getTLogVersion() < TLogVersion::V4 ) {
 			pop(upTo, txsTag, 0, popLocality);
 		} else {
@@ -1010,7 +1055,7 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		}
 	}
 
-	virtual void pop( Version upTo, Tag tag, Version durableKnownCommittedVersion, int8_t popLocality ) {
+	void pop(Version upTo, Tag tag, Version durableKnownCommittedVersion, int8_t popLocality) override {
 		if (upTo <= 0) return;
 		if( tag.locality == tagLocalityRemoteLog) {
 			popLogRouter(upTo, tag, durableKnownCommittedVersion, popLocality);
@@ -1110,7 +1155,7 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		return maxPopped;
 	}
 
-	virtual Future<Version> getTxsPoppedVersion() {
+	Future<Version> getTxsPoppedVersion() override {
 		return getPoppedTxs(this);
 	}
 
@@ -1162,7 +1207,7 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 	}
 
 	// Returns success after confirming that pushes in the current epoch are still possible
-	virtual Future<Void> confirmEpochLive(Optional<UID> debugID) {
+	Future<Void> confirmEpochLive(Optional<UID> debugID) override {
 		vector<Future<Void>> quorumResults;
 		for(auto& it : tLogs) {
 			if(it->isLocal && it->logServers.size()) {
@@ -1173,7 +1218,7 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		return waitForAll(quorumResults);
 	}
 
-	virtual Future<Void> endEpoch() {
+	Future<Void> endEpoch() override {
 		std::vector<Future<Void>> lockResults;
 		for( auto& logSet : tLogs ) {
 			for( auto& log : logSet->logServers ) {
@@ -1183,14 +1228,19 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		return waitForAll(lockResults);
 	}
 
-	virtual Future<Reference<ILogSystem>> newEpoch( RecruitFromConfigurationReply const& recr, Future<RecruitRemoteFromConfigurationReply> const& fRemoteWorkers, DatabaseConfiguration const& config, LogEpoch recoveryCount, int8_t primaryLocality, int8_t remoteLocality, std::vector<Tag> const& allTags, Reference<AsyncVar<bool>> const& recruitmentStalled ) {
-		// Call only after end_epoch() has successfully completed.  Returns a new epoch immediately following this one.  The new epoch
-		// is only provisional until the caller updates the coordinated DBCoreState
+	// Call only after end_epoch() has successfully completed.  Returns a new epoch immediately following this one.
+	// The new epoch is only provisional until the caller updates the coordinated DBCoreState.
+	Future<Reference<ILogSystem>> newEpoch(RecruitFromConfigurationReply const& recr,
+	                                       Future<RecruitRemoteFromConfigurationReply> const& fRemoteWorkers,
+	                                       DatabaseConfiguration const& config, LogEpoch recoveryCount,
+	                                       int8_t primaryLocality, int8_t remoteLocality,
+	                                       std::vector<Tag> const& allTags,
+	                                       Reference<AsyncVar<bool>> const& recruitmentStalled) override {
 		return newEpoch( Reference<TagPartitionedLogSystem>::addRef(this), recr, fRemoteWorkers, config, recoveryCount, primaryLocality, remoteLocality, allTags, recruitmentStalled );
 	}
 
-	virtual LogSystemConfig getLogSystemConfig() {
-		LogSystemConfig logSystemConfig;
+	LogSystemConfig getLogSystemConfig() override {
+		LogSystemConfig logSystemConfig(epoch);
 		logSystemConfig.logSystemType = logSystemType;
 		logSystemConfig.expectedLogSets = expectedLogSets;
 		logSystemConfig.logRouterTags = logRouterTags;
@@ -1198,6 +1248,8 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		logSystemConfig.recruitmentID = recruitmentID;
 		logSystemConfig.stopped = stopped;
 		logSystemConfig.recoveredAt = recoveredAt;
+		logSystemConfig.pseudoLocalities = pseudoLocalities;
+		logSystemConfig.oldestBackupEpoch = oldestBackupEpoch;
 		for (const Reference<LogSet>& logSet : tLogs) {
 			if (logSet->isLocal || remoteLogsWrittenToCoreState) {
 				logSystemConfig.tLogs.emplace_back(*logSet);
@@ -1212,7 +1264,7 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		return logSystemConfig;
 	}
 
-	virtual Standalone<StringRef> getLogsValue() {
+	Standalone<StringRef> getLogsValue() override {
 		vector<std::pair<UID, NetworkAddress>> logs;
 		vector<std::pair<UID, NetworkAddress>> oldLogs;
 		for(auto& t : tLogs) {
@@ -1234,7 +1286,7 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		return logsValue( logs, oldLogs );
 	}
 
-	virtual Future<Void> onLogSystemConfigChange() {
+	Future<Void> onLogSystemConfigChange() override {
 		std::vector<Future<Void>> changes;
 		changes.push_back(logSystemConfigChanged.onTrigger());
 		for(auto& t : tLogs) {
@@ -1257,7 +1309,7 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		return waitForAny(changes);
 	}
 
-	virtual Version getEnd() {
+	Version getEnd() override {
 		ASSERT( recoverAt.present() );
 		return recoverAt.get() + 1;
 	}
@@ -1269,7 +1321,7 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 			return std::numeric_limits<Version>::max();
 	}
 
-	virtual void getPushLocations(VectorRef<Tag> tags, std::vector<int>& locations, bool allLocations) {
+	void getPushLocations(VectorRef<Tag> tags, std::vector<int>& locations, bool allLocations) override {
 		int locationOffset = 0;
 		for(auto& log : tLogs) {
 			if(log->isLocal && log->logServers.size()) {
@@ -1279,22 +1331,103 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		}
 	}
 
-	virtual bool hasRemoteLogs() const {
+	bool hasRemoteLogs() const override {
 		return logRouterTags > 0 || pseudoLocalities.size() > 0;
 	}
 
-	virtual Tag getRandomRouterTag() const {
+	Tag getRandomRouterTag() const override {
 		return Tag(tagLocalityLogRouter, deterministicRandom()->randomInt(0, logRouterTags));
 	}
 
-	virtual Tag getRandomTxsTag() const {
+	Tag getRandomTxsTag() const override {
 		return Tag(tagLocalityTxs, deterministicRandom()->randomInt(0, txsTags));
 	}
 
-	virtual TLogVersion getTLogVersion() const {
+	TLogVersion getTLogVersion() const override {
 		return tLogs[0]->tLogVersion;
 	}
 
+	int getLogRouterTags() const override { return logRouterTags; }
+
+	Version getStartVersion() const override {
+		ASSERT(tLogs.size() > 0);
+		return tLogs[0]->startVersion;
+	}
+
+	std::map<LogEpoch, ILogSystem::EpochTagsVersionsInfo> getOldEpochTagsVersionsInfo() const override {
+		std::map<LogEpoch, EpochTagsVersionsInfo> epochInfos;
+		for (const auto& old : oldLogData) {
+			epochInfos.insert(
+			    { old.epoch, ILogSystem::EpochTagsVersionsInfo(old.logRouterTags, old.epochBegin, old.epochEnd) });
+			TraceEvent("OldEpochTagsVersions", dbgid)
+			    .detail("Epoch", old.epoch)
+			    .detail("Tags", old.logRouterTags)
+			    .detail("BeginVersion", old.epochBegin)
+			    .detail("EndVersion", old.epochEnd);
+		}
+		return epochInfos;
+	}
+
+	inline Reference<LogSet> getEpochLogSet(LogEpoch epoch) const {
+		for (const auto& old : oldLogData) {
+			if (epoch == old.epoch) return old.tLogs[0];
+		}
+		return Reference<LogSet>(nullptr);
+	}
+
+	void setBackupWorkers(const std::vector<InitializeBackupReply>& replies) override {
+		ASSERT(tLogs.size() > 0);
+
+		Reference<LogSet> logset = tLogs[0];  // Master recruits this epoch's worker first.
+		LogEpoch logsetEpoch = this->epoch;
+		oldestBackupEpoch = this->epoch;
+		for (const auto& reply : replies) {
+			Reference<AsyncVar<OptionalInterface<BackupInterface>>> worker(new AsyncVar<OptionalInterface<BackupInterface>>(OptionalInterface<BackupInterface>(reply.interf)));
+			if (reply.backupEpoch != logsetEpoch) {
+				// find the logset from oldLogData
+				logsetEpoch = reply.backupEpoch;
+				oldestBackupEpoch = std::min(oldestBackupEpoch, logsetEpoch);
+				logset = getEpochLogSet(logsetEpoch);
+				ASSERT(logset.isValid());
+			}
+			logset->backupWorkers.push_back(worker);
+		}
+		backupWorkerChanged.trigger();
+	}
+
+	bool removeBackupWorker(const BackupWorkerDoneRequest& req) override {
+		bool removed = false;
+		Reference<LogSet> logset = getEpochLogSet(req.backupEpoch);
+		if (logset.isValid()) {
+			for (auto it = logset->backupWorkers.begin(); it != logset->backupWorkers.end(); it++) {
+				if (it->getPtr()->get().interf().id() == req.workerUID) {
+					logset->backupWorkers.erase(it);
+					removed = true;
+					break;
+				}
+			}
+		}
+
+		if (removed) {
+			oldestBackupEpoch = epoch;
+			for (const auto& old : oldLogData) {
+				if (old.epoch < oldestBackupEpoch && old.tLogs[0]->backupWorkers.size() > 0) {
+					oldestBackupEpoch = old.epoch;
+				}
+			}
+			backupWorkerChanged.trigger();
+		}
+
+		TraceEvent("RemoveBackupWorker", dbgid)
+		    .detail("Removed", removed)
+		    .detail("BackupEpoch", req.backupEpoch)
+		    .detail("WorkerID", req.workerUID)
+		    .detail("OldestBackupEpoch", oldestBackupEpoch);
+		return removed;
+	}
+
+	LogEpoch getOldestBackupEpoch() const override { return oldestBackupEpoch; }
+
 	ACTOR static Future<Void> monitorLog(Reference<AsyncVar<OptionalInterface<TLogInterface>>> logServer, Reference<AsyncVar<bool>> failed) {
 		state Future<Void> waitFailure;
 		loop {
@@ -1403,7 +1536,7 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 
 		if (!prevState.tLogs.size()) {
 			// This is a brand new database
-			Reference<TagPartitionedLogSystem> logSystem( new TagPartitionedLogSystem(dbgid, locality) );
+			Reference<TagPartitionedLogSystem> logSystem( new TagPartitionedLogSystem(dbgid, locality, 0) );
 			logSystem->logSystemType = prevState.logSystemType;
 			logSystem->recoverAt = 0;
 			logSystem->knownCommittedVersion = 0;
@@ -1473,7 +1606,11 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 									modifiedState.oldTLogData[i].tLogs.push_back(coreSet);
 									modifiedState.oldTLogData[i].tLogs[0].isLocal = true;
 									modifiedState.oldTLogData[i].logRouterTags = 0;
-									modifiedState.oldTLogData[i].epochEnd = ( i == 0 ? modifiedState.tLogs[0].startVersion : modifiedState.oldTLogData[i-1].tLogs[0].startVersion );
+									modifiedState.oldTLogData[i].epochBegin =
+									    modifiedState.oldTLogData[i].tLogs[0].startVersion;
+									modifiedState.oldTLogData[i].epochEnd =
+									    (i == 0 ? modifiedState.tLogs[0].startVersion
+									            : modifiedState.oldTLogData[i - 1].tLogs[0].startVersion);
 									modifiedLogSets++;
 								}
 								break;
@@ -1642,7 +1779,8 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 			if(maxEnd > 0 && (!lastEnd.present() || maxEnd < lastEnd.get())) {
 				TEST( lastEnd.present() );  // Restarting recovery at an earlier point
 
-				Reference<TagPartitionedLogSystem> logSystem( new TagPartitionedLogSystem(dbgid, locality) );
+				Reference<TagPartitionedLogSystem> logSystem(
+				    new TagPartitionedLogSystem(dbgid, locality, prevState.recoveryCount));
 
 				lastEnd = minEnd;
 				logSystem->tLogs = logServers;
@@ -1819,10 +1957,10 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		return Void();
 	}
 
-	static Version getMaxLocalStartVersion(std::vector<Reference<LogSet>>& tLogs) {
+	static Version getMaxLocalStartVersion(const std::vector<Reference<LogSet>>& tLogs) {
 		Version maxStart = 0;
 		for (const auto& logSet : tLogs) {
-			if(logSet->isLocal) {
+			if (logSet->isLocal) {
 				maxStart = std::max(maxStart, logSet->startVersion);
 			}
 		}
@@ -1880,11 +2018,14 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		}
 
 		state vector<Future<TLogInterface>> logRouterInitializationReplies;
-		for( int i = 0; i < self->logRouterTags; i++) {
+		const Version startVersion = oldLogSystem->logRouterTags == 0
+			? oldLogSystem->recoverAt.get() + 1
+			: std::max(self->tLogs[0]->startVersion, logSet->startVersion);
+		for (int i = 0; i < self->logRouterTags; i++) {
 			InitializeLogRouterRequest req;
 			req.recoveryCount = recoveryCount;
 			req.routerTag = Tag(tagLocalityLogRouter, i);
-			req.startVersion = oldLogSystem->logRouterTags == 0 ? oldLogSystem->recoverAt.get() + 1 : std::max(self->tLogs[0]->startVersion, logSet->startVersion);
+			req.startVersion = startVersion;
 			req.tLogLocalities = localities;
 			req.tLogPolicy = logSet->tLogPolicy;
 			req.locality = remoteLocality;
@@ -1987,7 +2128,8 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 	ACTOR static Future<Reference<ILogSystem>> newEpoch( Reference<TagPartitionedLogSystem> oldLogSystem, RecruitFromConfigurationReply recr, Future<RecruitRemoteFromConfigurationReply> fRemoteWorkers, DatabaseConfiguration configuration, LogEpoch recoveryCount,
 		int8_t primaryLocality, int8_t remoteLocality, std::vector<Tag> allTags, Reference<AsyncVar<bool>> recruitmentStalled ) {
 		state double startTime = now();
-		state Reference<TagPartitionedLogSystem> logSystem( new TagPartitionedLogSystem(oldLogSystem->getDebugID(), oldLogSystem->locality) );
+		state Reference<TagPartitionedLogSystem> logSystem(
+		    new TagPartitionedLogSystem(oldLogSystem->getDebugID(), oldLogSystem->locality, recoveryCount));
 		logSystem->logSystemType = LogSystemType::tagPartitioned;
 		logSystem->expectedLogSets = 1;
 		logSystem->recoveredAt = oldLogSystem->recoverAt;
@@ -1996,10 +2138,18 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		logSystem->txsTags = configuration.tLogVersion >= TLogVersion::V4 ? recr.tLogs.size() : 0;
 		oldLogSystem->recruitmentID = logSystem->recruitmentID;
 
+		logSystem->logRouterTags = recr.tLogs.size() * std::max<int>(1, configuration.desiredLogRouterCount / std::max<int>(1, recr.tLogs.size()));
 		if(configuration.usableRegions > 1) {
-			logSystem->logRouterTags = recr.tLogs.size() * std::max<int>(1, configuration.desiredLogRouterCount / std::max<int>(1,recr.tLogs.size()));
 			logSystem->expectedLogSets++;
 			logSystem->addPseudoLocality(tagLocalityLogRouterMapped);
+			logSystem->addPseudoLocality(tagLocalityBackup);
+			TraceEvent("AddPseudoLocality", logSystem->getDebugID())
+			    .detail("Locality1", "LogRouterMapped")
+			    .detail("Locality2", "Backup");
+		} else {
+			// Single region uses log router tag for backup workers.
+			logSystem->addPseudoLocality(tagLocalityBackup);
+			TraceEvent("AddPseudoLocality", logSystem->getDebugID()).detail("Locality", "Backup");
 		}
 
 		logSystem->tLogs.emplace_back(new LogSet());
@@ -2050,10 +2200,12 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		if(oldLogSystem->tLogs.size()) {
 			logSystem->oldLogData.emplace_back();
 			logSystem->oldLogData[0].tLogs = oldLogSystem->tLogs;
+			logSystem->oldLogData[0].epochBegin = oldLogSystem->tLogs[0]->startVersion;
 			logSystem->oldLogData[0].epochEnd = oldLogSystem->knownCommittedVersion + 1;
 			logSystem->oldLogData[0].logRouterTags = oldLogSystem->logRouterTags;
 			logSystem->oldLogData[0].txsTags = oldLogSystem->txsTags;
 			logSystem->oldLogData[0].pseudoLocalities = oldLogSystem->pseudoLocalities;
+			logSystem->oldLogData[0].epoch = oldLogSystem->epoch;
 		}
 		logSystem->oldLogData.insert(logSystem->oldLogData.end(), oldLogSystem->oldLogData.begin(), oldLogSystem->oldLogData.end());
 
@@ -2255,7 +2407,7 @@ struct TagPartitionedLogSystem : ILogSystem, ReferenceCounted<TagPartitionedLogS
 		if(configuration.usableRegions > 1) {
 			logSystem->hasRemoteServers = true;
 			logSystem->remoteRecovery = TagPartitionedLogSystem::newRemoteEpoch(logSystem.getPtr(), oldLogSystem, fRemoteWorkers, configuration, recoveryCount, remoteLocality, allTags);
-			if(oldLogSystem->logRouterTags == 0) {
+			if (oldLogSystem->tLogs.size() > 0 && oldLogSystem->tLogs[0]->locality == tagLocalitySpecial) {
 				//The wait is required so that we know both primary logs and remote logs have copied the data between the known committed version and the recovery version.
 				//FIXME: we can remove this wait once we are able to have log routers which can ship data to the remote logs without using log router tags.
 				wait(logSystem->remoteRecovery);

fdbserver/WorkerInterface.actor.h

@@ -25,6 +25,7 @@
 #elif !defined(FDBSERVER_WORKERINTERFACE_ACTOR_H)
 	#define FDBSERVER_WORKERINTERFACE_ACTOR_H
 
+#include "fdbserver/BackupInterface.h"
 #include "fdbserver/DataDistributorInterface.h"
 #include "fdbserver/MasterInterface.h"
 #include "fdbserver/TLogInterface.h"
@@ -50,6 +51,7 @@ struct WorkerInterface {
 	RequestStream< struct InitializeResolverRequest > resolver;
 	RequestStream< struct InitializeStorageRequest > storage;
 	RequestStream< struct InitializeLogRouterRequest > logRouter;
+	RequestStream< struct InitializeBackupRequest > backup;
 
 	RequestStream< struct LoadedPingRequest > debugPing;
 	RequestStream< struct CoordinationPingMessage > coordinationPing;
@@ -82,7 +84,7 @@ struct WorkerInterface {
 
 	template <class Ar>
 	void serialize(Ar& ar) {
-		serializer(ar, clientInterface, locality, tLog, master, masterProxy, dataDistributor, ratekeeper, resolver, storage, logRouter, debugPing, coordinationPing, waitFailure, setMetricsRate, eventLogRequest, traceBatchDumpRequest, testerInterface, diskStoreRequest, execReq, workerSnapReq);
+		serializer(ar, clientInterface, locality, tLog, master, masterProxy, dataDistributor, ratekeeper, resolver, storage, logRouter, debugPing, coordinationPing, waitFailure, setMetricsRate, eventLogRequest, traceBatchDumpRequest, testerInterface, diskStoreRequest, execReq, workerSnapReq, backup);
 	}
 };
 
@@ -122,7 +124,7 @@ struct InitializeTLogRequest {
 
 	ReplyPromise< struct TLogInterface > reply;
 
-	InitializeTLogRequest() {}
+	InitializeTLogRequest() : recoverFrom(0) {}
 
 	template <class Ar>
 	void serialize( Ar& ar ) {
@@ -146,6 +148,40 @@ struct InitializeLogRouterRequest {
 	}
 };
 
+struct InitializeBackupReply {
+	constexpr static FileIdentifier file_identifier = 63843557;
+	struct BackupInterface interf;
+	LogEpoch backupEpoch;
+
+	InitializeBackupReply() = default;
+	InitializeBackupReply(BackupInterface interface, LogEpoch e) : interf(interface), backupEpoch(e) {}
+
+	template <class Ar>
+	void serialize(Ar& ar) {
+		serializer(ar, interf, backupEpoch);
+	}
+};
+
+struct InitializeBackupRequest {
+	constexpr static FileIdentifier file_identifier = 68354279;
+	UID reqId;
+	LogEpoch recruitedEpoch; // The epoch the worker is recruited.
+	LogEpoch backupEpoch; // The epoch the worker should work on. If different from the recruitedEpoch, then it refers
+	                      // to some previous epoch with unfinished work.
+	Tag routerTag;
+	Version startVersion;
+	Optional<Version> endVersion;
+	ReplyPromise<struct InitializeBackupReply> reply;
+
+	InitializeBackupRequest() = default;
+	explicit InitializeBackupRequest(UID id) : reqId(id) {}
+
+	template <class Ar>
+	void serialize(Ar& ar) {
+		serializer(ar, reqId, recruitedEpoch, backupEpoch, routerTag, startVersion, endVersion, reply);
+	}
+};
+
 // FIXME: Rename to InitializeMasterRequest, etc
 struct RecruitMasterRequest {
 	constexpr static FileIdentifier file_identifier = 12684574;
@@ -399,6 +435,7 @@ struct Role {
 	static const Role RATEKEEPER;
 	static const Role STORAGE_CACHE;
 	static const Role COORDINATOR;
+	static const Role BACKUP;
 
 	std::string roleName;
 	std::string abbreviation;
@@ -468,6 +505,7 @@ ACTOR Future<Void> logRouter(TLogInterface interf, InitializeLogRouterRequest re
 ACTOR Future<Void> dataDistributor(DataDistributorInterface ddi, Reference<AsyncVar<ServerDBInfo>> db);
 ACTOR Future<Void> ratekeeper(RatekeeperInterface rki, Reference<AsyncVar<ServerDBInfo>> db);
 ACTOR Future<Void> storageCache(StorageServerInterface interf, uint16_t id, Reference<AsyncVar<ServerDBInfo>> db);
+ACTOR Future<Void> backupWorker(BackupInterface bi, InitializeBackupRequest req, Reference<AsyncVar<ServerDBInfo>> db);
 
 void registerThreadForProfiling();
 void updateCpuProfiler(ProfilerRequest req);

fdbserver/fdbserver.actor.cpp

@@ -1719,8 +1719,11 @@ int main(int argc, char* argv[]) {
 			std::vector<std::string> directories = platform::listDirectories( dataFolder );
 			for(int i = 0; i < directories.size(); i++)
 				if (directories[i].size() != 32 && directories[i] != "." && directories[i] != ".." &&
-				    directories[i] != "backups" && directories[i].find("snap") == std::string::npos) {
-					TraceEvent(SevError, "IncompatibleDirectoryFound").detail("DataFolder", dataFolder).detail("SuspiciousFile", directories[i]);
+				    directories[i] != "backups" && directories[i].find("snap") == std::string::npos &&
+				    directories[i] != "mutation_backups") {
+					TraceEvent(SevError, "IncompatibleDirectoryFound")
+					    .detail("DataFolder", dataFolder)
+					    .detail("SuspiciousFile", directories[i]);
 					fprintf(stderr, "ERROR: Data folder `%s' had non fdb file `%s'; please use clean, fdb-only folder\n", dataFolder.c_str(), directories[i].c_str());
 					flushAndExit(FDB_EXIT_ERROR);
 				}

fdbserver/fdbserver.vcxproj

@@ -34,6 +34,8 @@
     <ActorCompiler Include="worker.actor.cpp" />
   </ItemGroup>
   <ItemGroup>
+    <ActorCompiler Include="BackupProgress.actor.cpp" />
+    <ActorCompiler Include="BackupWorker.actor.cpp" />
     <ActorCompiler Include="VersionedBTree.actor.cpp" />
     <ActorCompiler Include="Coordination.actor.cpp" />
     <ActorCompiler Include="CoordinatedState.actor.cpp" />
@@ -172,6 +174,10 @@
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="ApplyMetadataMutation.h" />
+    <ClInclude Include="BackupInterface.h" />
+    <ActorCompiler Include="BackupProgress.actor.h">
+          <EnableCompile>false</EnableCompile>
+    </ActorCompiler>
     <ClInclude Include="ClusterRecruitmentInterface.h" />
     <ClInclude Include="ConflictSet.h" />
     <ClInclude Include="CoordinatedState.h" />

fdbserver/fdbserver.vcxproj.filters

@@ -1,6 +1,8 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <ItemGroup>
+    <ActorCompiler Include="BackupProgress.actor.cpp" />
+    <ActorCompiler Include="BackupWorker.actor.cpp" />
     <ActorCompiler Include="ClusterController.actor.cpp" />
     <ActorCompiler Include="DataDistribution.actor.cpp" />
     <ActorCompiler Include="DataDistributionQueue.actor.cpp" />
@@ -322,6 +324,8 @@
     <ClCompile Include="LatencyBandConfig.cpp" />
   </ItemGroup>
   <ItemGroup>
+    <ClInclude Include="BackupInterface.h" />
+    <ClInclude Include="BackupProgress.h" />
     <ClInclude Include="ConflictSet.h" />
     <ClInclude Include="DataDistribution.actor.h" />
     <ClInclude Include="DataDistributorInterface.h" />

fdbserver/masterserver.actor.cpp

@@ -29,6 +29,8 @@
 #include "fdbserver/DataDistribution.actor.h"
 #include "fdbserver/Knobs.h"
 #include <iterator>
+#include "fdbserver/BackupProgress.actor.h"
+#include "fdbserver/MasterInterface.h"
 #include "fdbserver/WaitFailure.h"
 #include "fdbserver/WorkerInterface.actor.h"
 #include "fdbserver/ClusterRecruitmentInterface.h"
@@ -128,7 +130,7 @@ private:
 		if(finalWrite) {
 			self->finalWriteStarted = true;
 		}
-		
+
 		try {
 			wait( self->cstate.setExclusive( BinaryWriter::toValue(newState, IncludeVersion()) ) );
 		} catch (Error& e) {
@@ -194,16 +196,16 @@ struct MasterData : NonCopyable, ReferenceCounted<MasterData> {
 		return maxLocality + 1;
 	}
 
-	vector< MasterProxyInterface > proxies;
-	vector< MasterProxyInterface > provisionalProxies;
-	vector< ResolverInterface > resolvers;
+	std::vector<MasterProxyInterface> proxies;
+	std::vector<MasterProxyInterface> provisionalProxies;
+	std::vector<ResolverInterface> resolvers;
 
 	std::map<UID, ProxyVersionReplies> lastProxyVersionReplies;
 
 	Standalone<StringRef> dbId;
 
 	MasterInterface myInterface;
-	ClusterControllerFullInterface clusterController;  // If the cluster controller changes, this master will die, so this is immutable.
+	const ClusterControllerFullInterface clusterController;  // If the cluster controller changes, this master will die, so this is immutable.
 
 	ReusableCoordinatedState cstate;
 	Promise<Void> cstateUpdated;
@@ -219,9 +221,11 @@ struct MasterData : NonCopyable, ReferenceCounted<MasterData> {
 	PromiseStream<Future<Void>> addActor;
 	Reference<AsyncVar<bool>> recruitmentStalled;
 	bool forceRecovery;
+	bool neverCreated;
 	int8_t safeLocality;
 	int8_t primaryLocality;
-	bool neverCreated;
+
+	std::vector<WorkerInterface> backupWorkers; // Recruited backup workers from cluster controller.
 
 	MasterData(
 		Reference<AsyncVar<ServerDBInfo>> const& dbInfo,
@@ -465,14 +469,14 @@ Future<Void> sendMasterRegistration( MasterData* self, LogSystemConfig const& lo
 
 ACTOR Future<Void> updateRegistration( Reference<MasterData> self, Reference<ILogSystem> logSystem ) {
 	state Database cx = openDBOnServer(self->dbInfo, TaskPriority::DefaultEndpoint, true, true);
-	state Future<Void> trigger =  self->registrationTrigger.onTrigger();
+	state Future<Void> trigger = self->registrationTrigger.onTrigger();
 	state Future<Void> updateLogsKey;
 
 	loop {
 		wait( trigger );
 		wait( delay( .001 ) );  // Coalesce multiple changes
 
-		trigger =  self->registrationTrigger.onTrigger();
+		trigger = self->registrationTrigger.onTrigger();
 
 		TraceEvent("MasterUpdateRegistration", self->dbgid).detail("RecoveryCount", self->cstate.myDBState.recoveryCount).detail("Logs", describe(logSystem->getLogSystemConfig().tLogs));
 
@@ -592,20 +596,23 @@ ACTOR Future<vector<Standalone<CommitTransactionRef>>> recruitEverything( Refere
 			self->remoteDcIds.push_back(recruits.dcId.get() == self->configuration.regions[0].dcId ? self->configuration.regions[1].dcId : self->configuration.regions[0].dcId);
 		}
 	}
-	
+	self->backupWorkers.swap(recruits.backupWorkers);
+
 	TraceEvent("MasterRecoveryState", self->dbgid)
 		.detail("StatusCode", RecoveryStatus::initializing_transaction_servers)
 		.detail("Status", RecoveryStatus::names[RecoveryStatus::initializing_transaction_servers])
 		.detail("Proxies", recruits.proxies.size())
 		.detail("TLogs", recruits.tLogs.size())
 		.detail("Resolvers", recruits.resolvers.size())
+		.detail("BackupWorkers", self->backupWorkers.size())
 		.trackLatest("MasterRecoveryState");
 
 	// Actually, newSeedServers does both the recruiting and initialization of the seed servers; so if this is a brand new database we are sort of lying that we are
 	// past the recruitment phase.  In a perfect world we would split that up so that the recruitment part happens above (in parallel with recruiting the transaction servers?).
 	wait( newSeedServers( self, recruits, seedServers ) );
 	state vector<Standalone<CommitTransactionRef>> confChanges;
-	wait( newProxies( self, recruits ) && newResolvers( self, recruits ) && newTLogServers( self, recruits, oldLogSystem, &confChanges ) );
+	wait(newProxies(self, recruits) && newResolvers(self, recruits) &&
+	     newTLogServers(self, recruits, oldLogSystem, &confChanges));
 	return confChanges;
 }
 
@@ -1092,6 +1099,7 @@ static std::set<int> const& normalMasterErrors() {
 		s.insert( error_code_master_tlog_failed );
 		s.insert( error_code_master_proxy_failed );
 		s.insert( error_code_master_resolver_failed );
+		s.insert( error_code_master_backup_worker_failed );
 		s.insert( error_code_recruitment_failed );
 		s.insert( error_code_no_more_servers );
 		s.insert( error_code_master_recovery_failed );
@@ -1194,8 +1202,7 @@ ACTOR Future<Void> trackTlogRecovery( Reference<MasterData> self, Reference<Asyn
 	}
 }
 
-ACTOR Future<Void> configurationMonitor( Reference<MasterData> self ) {
-	state Database cx = openDBOnServer(self->dbInfo, TaskPriority::DefaultEndpoint, true, true);
+ACTOR Future<Void> configurationMonitor(Reference<MasterData> self, Database cx) {
 	loop {
 		state ReadYourWritesTransaction tr(cx);
 
@@ -1227,6 +1234,75 @@ ACTOR Future<Void> configurationMonitor( Reference<MasterData> self ) {
 	}
 }
 
+ACTOR static Future<Void> recruitBackupWorkers(Reference<MasterData> self, Database cx) {
+	ASSERT(self->backupWorkers.size() > 0);
+
+	state LogEpoch epoch = self->cstate.myDBState.recoveryCount;
+	state Reference<BackupProgress> backupProgress(
+	    new BackupProgress(self->dbgid, self->logSystem->getOldEpochTagsVersionsInfo()));
+	state Future<Void> gotProgress = getBackupProgress(cx, self->dbgid, backupProgress);
+	state std::vector<Future<InitializeBackupReply>> initializationReplies;
+
+	state std::vector<std::pair<UID, Tag>> idsTags; // worker IDs and tags for current epoch
+	state int logRouterTags = self->logSystem->getLogRouterTags();
+	for (int i = 0; i < logRouterTags; i++) {
+		idsTags.emplace_back(deterministicRandom()->randomUniqueID(), Tag(tagLocalityLogRouter, i));
+	}
+
+	const Version startVersion = self->logSystem->getStartVersion();
+	state int i = 0;
+	for (; i < logRouterTags; i++) {
+		const auto& worker = self->backupWorkers[i % self->backupWorkers.size()];
+		InitializeBackupRequest req(idsTags[i].first);
+		req.recruitedEpoch = epoch;
+		req.backupEpoch = epoch;
+		req.routerTag = idsTags[i].second;
+		req.startVersion = startVersion;
+		TraceEvent("BackupRecruitment", self->dbgid)
+		    .detail("BKID", req.reqId)
+		    .detail("Tag", req.routerTag.toString())
+		    .detail("Epoch", epoch)
+		    .detail("BackupEpoch", epoch)
+		    .detail("StartVersion", req.startVersion);
+		initializationReplies.push_back(
+		    transformErrors(throwErrorOr(worker.backup.getReplyUnlessFailedFor(
+		                        req, SERVER_KNOBS->BACKUP_TIMEOUT, SERVER_KNOBS->MASTER_FAILURE_SLOPE_DURING_RECOVERY)),
+		                    master_backup_worker_failed()));
+	}
+
+	wait(gotProgress);
+	std::map<std::pair<LogEpoch, Version>, std::map<Tag, Version>> toRecruit = backupProgress->getUnfinishedBackup();
+	for (const auto& [epochVersion, tagVersions] : toRecruit) {
+		for (const auto& [tag, version] : tagVersions) {
+			const auto& worker = self->backupWorkers[i % self->backupWorkers.size()];
+			i++;
+			InitializeBackupRequest req(deterministicRandom()->randomUniqueID());
+			req.recruitedEpoch = epoch;
+			req.backupEpoch = epochVersion.first;
+			req.routerTag = tag;
+			req.startVersion = version; // savedVersion + 1
+			req.endVersion = epochVersion.second - 1;
+			TraceEvent("BackupRecruitment", self->dbgid)
+			    .detail("BKID", req.reqId)
+			    .detail("Tag", req.routerTag.toString())
+			    .detail("Epoch", epoch)
+			    .detail("BackupEpoch", req.backupEpoch)
+			    .detail("StartVersion", req.startVersion)
+			    .detail("EndVersion", req.endVersion.get());
+			initializationReplies.push_back(transformErrors(
+			    throwErrorOr(worker.backup.getReplyUnlessFailedFor(req, SERVER_KNOBS->BACKUP_TIMEOUT,
+			                                                       SERVER_KNOBS->MASTER_FAILURE_SLOPE_DURING_RECOVERY)),
+			    master_backup_worker_failed()));
+		}
+	}
+
+	std::vector<InitializeBackupReply> newRecruits = wait(getAll(initializationReplies));
+	self->logSystem->setBackupWorkers(newRecruits);
+	TraceEvent("BackupRecruitmentDone", self->dbgid);
+	self->registrationTrigger.trigger();
+	return Void();
+}
+
 ACTOR Future<Void> masterCore( Reference<MasterData> self ) {
 	state TraceInterval recoveryInterval("MasterRecovery");
 	state double recoverStartTime = now();
@@ -1251,6 +1327,9 @@ ACTOR Future<Void> masterCore( Reference<MasterData> self ) {
 		.detail("MyRecoveryCount", self->cstate.prevDBState.recoveryCount+2)
 		.detail("ForceRecovery", self->forceRecovery)
 		.trackLatest("MasterRecoveryState");
+	//for (const auto& old : self->cstate.prevDBState.oldTLogData) {
+	//	TraceEvent("BWReadCoreState", self->dbgid).detail("Epoch", old.epoch).detail("Version", old.epochEnd);
+	//}
 
 	state Reference<AsyncVar<Reference<ILogSystem>>> oldLogSystems( new AsyncVar<Reference<ILogSystem>> );
 	state Future<Void> recoverAndEndEpoch = ILogSystem::recoverAndEndEpoch(oldLogSystems, self->dbgid, self->cstate.prevDBState, self->myInterface.tlogRejoin.getFuture(), self->myInterface.locality, &self->forceRecovery);
@@ -1444,7 +1523,9 @@ ACTOR Future<Void> masterCore( Reference<MasterData> self ) {
 		self->addActor.send( resolutionBalancing(self) );
 
 	self->addActor.send( changeCoordinators(self) );
-	self->addActor.send( configurationMonitor( self ) );
+	Database cx = openDBOnServer(self->dbInfo, TaskPriority::DefaultEndpoint, true, true);
+	self->addActor.send(configurationMonitor(self, cx));
+	self->addActor.send(recruitBackupWorkers(self, cx));
 
 	wait( Future<Void>(Never()) );
 	throw internal_error();
@@ -1473,6 +1554,12 @@ ACTOR Future<Void> masterServer( MasterInterface mi, Reference<AsyncVar<ServerDB
 					throw worker_removed();
 				}
 			}
+			when(BackupWorkerDoneRequest req = waitNext(mi.notifyBackupWorkerDone.getFuture())) {
+				if (self->logSystem.isValid() && self->logSystem->removeBackupWorker(req)) {
+					self->registrationTrigger.trigger();
+				}
+				req.reply.send(Void());
+			}
 			when (wait(collection) ) { ASSERT(false); throw internal_error(); }
 		}
 	} catch (Error& e) {
@@ -1488,9 +1575,9 @@ ACTOR Future<Void> masterServer( MasterInterface mi, Reference<AsyncVar<ServerDB
 		TEST(err.code() == error_code_master_tlog_failed);  // Master: terminated because of a tLog failure
 		TEST(err.code() == error_code_master_proxy_failed);  // Master: terminated because of a proxy failure
 		TEST(err.code() == error_code_master_resolver_failed);  // Master: terminated because of a resolver failure
+		TEST(err.code() == error_code_master_backup_worker_failed);  // Master: terminated because of a backup worker failure
 
-		if (normalMasterErrors().count(err.code()))
-		{
+		if (normalMasterErrors().count(err.code())) {
 			TraceEvent("MasterTerminated", mi.id()).error(err);
 			return Void();
 		}

fdbserver/worker.actor.cpp

@@ -26,6 +26,7 @@
 #include "fdbrpc/simulator.h"
 #include "fdbclient/NativeAPI.actor.h"
 #include "fdbclient/MetricLogger.h"
+#include "fdbserver/BackupInterface.h"
 #include "fdbserver/WorkerInterface.actor.h"
 #include "fdbserver/IKeyValueStore.h"
 #include "fdbserver/WaitFailure.h"
@@ -1114,6 +1115,19 @@ ACTOR Future<Void> workerServer(
 				TraceEvent("Ratekeeper_InitRequest", req.reqId).detail("RatekeeperId", recruited.id());
 				req.reply.send(recruited);
 			}
+			when (InitializeBackupRequest req = waitNext(interf.backup.getFuture())) {
+				BackupInterface recruited(locality);
+				recruited.initEndpoints();
+
+				startRole(Role::BACKUP, recruited.id(), interf.id());
+				DUMPTOKEN(recruited.waitFailure);
+
+				Future<Void> backupProcess = backupWorker(recruited, req, dbInfo);
+				errorForwarders.add(forwardError(errors, Role::BACKUP, recruited.id(), backupProcess));
+				TraceEvent("Backup_InitRequest", req.reqId).detail("BackupId", recruited.id());
+				InitializeBackupReply reply(recruited, req.backupEpoch);
+				req.reply.send(reply);
+			}
 			when( InitializeTLogRequest req = waitNext(interf.tLog.getFuture()) ) {
 				// For now, there's a one-to-one mapping of spill type to TLogVersion.
 				// With future work, a particular version of the TLog can support multiple
@@ -1545,3 +1559,4 @@ const Role Role::DATA_DISTRIBUTOR("DataDistributor", "DD");
 const Role Role::RATEKEEPER("Ratekeeper", "RK");
 const Role Role::STORAGE_CACHE("StorageCache", "SC");
 const Role Role::COORDINATOR("Coordinator", "CD");
+const Role Role::BACKUP("Backup", "BK");

fdbserver/workloads/ConsistencyCheck.actor.cpp

@@ -121,7 +121,8 @@ struct ConsistencyCheckWorkload : TestWorkload
 			}
 
 			try {
-				wait(timeoutError(quietDatabase(cx, self->dbInfo, "ConsistencyCheckStart", 0, 1e5, 0, 0), self->quiescentWaitTimeout));  // FIXME: should be zero?
+				wait(timeoutError(quietDatabase(cx, self->dbInfo, "ConsistencyCheckStart", 0, 1e5, 0, 0),
+				                  self->quiescentWaitTimeout)); // FIXME: should be zero?
 			}
 			catch (Error& e) {
 				TraceEvent("ConsistencyCheck_QuietDatabaseError").error(e);
@@ -272,14 +273,12 @@ struct ConsistencyCheckWorkload : TestWorkload
 					try
 					{
 						int64_t maxStorageServerQueueSize = wait(getMaxStorageServerQueueSize(cx, self->dbInfo));
-						if(maxStorageServerQueueSize > 0)
-						{
-							TraceEvent("ConsistencyCheck_NonZeroStorageServerQueue").detail("MaxQueueSize", maxStorageServerQueueSize);
-							self->testFailure("Non-zero storage server queue size");
+						if (maxStorageServerQueueSize > 0) {
+							TraceEvent("ConsistencyCheck_ExceedStorageServerQueueLimit")
+							    .detail("MaxQueueSize", maxStorageServerQueueSize);
+							self->testFailure("Storage server queue size exceeds limit");
 						}
-					}
-					catch(Error& e)
-					{
+					} catch (Error& e) {
 						if(e.code() == error_code_attribute_not_found)
 						{
 							TraceEvent("ConsistencyCheck_StorageQueueSizeError").error(e).detail("Reason", "Could not read queue size");

flow/ProtocolVersion.h

@@ -89,6 +89,7 @@ public: // introduced features
 	PROTOCOL_VERSION_FEATURE(0x0FDB00B061070000LL, PseudoLocalities);
 	PROTOCOL_VERSION_FEATURE(0x0FDB00B061070000LL, ShardedTxsTags);
 	PROTOCOL_VERSION_FEATURE(0x0FDB00B063000000LL, UnifiedTLogSpilling);
+	PROTOCOL_VERSION_FEATURE(0x0FDB00B063010000LL, BackupWorker);
 };
 
 // These impact both communications and the deserialization of certain database and IKeyValueStore keys.

flow/error_definitions.h

@@ -86,6 +86,7 @@ ERROR( please_reboot_delete, 1208, "Reboot of server process requested, with del
 ERROR( master_proxy_failed, 1209, "Master terminating because a Proxy failed" )
 ERROR( master_resolver_failed, 1210, "Master terminating because a Resolver failed" )
 ERROR( server_overloaded, 1211, "Server is under too much load and cannot respond" )
+ERROR( master_backup_worker_failed, 1212, "Master terminating because a backup worker failed")
 
 // 15xx Platform errors
 ERROR( platform_error, 1500, "Platform error" )