Add knob value changes to fdbdecode

E.g., HTTP_VERBOSE_LEVEL, and HTTP_REQUEST_AWS_V4_HEADER knobs.

fdbbackup/FileConverter.h

@@ -46,6 +46,7 @@ enum {
 	OPT_HEX_KEY_PREFIX,
 	OPT_BEGIN_VERSION_FILTER,
 	OPT_END_VERSION_FILTER,
+	OPT_KNOB,
 	OPT_HELP
 };
 
@@ -72,6 +73,7 @@ CSimpleOpt::SOption gConverterOptions[] = { { OPT_CONTAINER, "-r", SO_REQ_SEP },
 	                                        { OPT_HEX_KEY_PREFIX, "--hex-prefix", SO_REQ_SEP },
 	                                        { OPT_BEGIN_VERSION_FILTER, "--begin-version-filter", SO_REQ_SEP },
 	                                        { OPT_END_VERSION_FILTER, "--end-version-filter", SO_REQ_SEP },
+	                                        { OPT_KNOB, "--knob-", SO_REQ_SEP },
 	                                        { OPT_HELP, "-?", SO_NONE },
 	                                        { OPT_HELP, "-h", SO_NONE },
 	                                        { OPT_HELP, "--help", SO_NONE },

fdbbackup/FileDecoder.actor.cpp

@@ -26,17 +26,21 @@
 #include <vector>
 
 #include "fdbbackup/BackupTLSConfig.h"
+#include "fdbclient/BuildFlags.h"
+#include "fdbbackup/FileConverter.h"
 #include "fdbclient/BackupAgent.actor.h"
 #include "fdbclient/BackupContainer.h"
-#include "fdbbackup/FileConverter.h"
 #include "fdbclient/CommitTransaction.h"
 #include "fdbclient/FDBTypes.h"
+#include "fdbclient/IKnobCollection.h"
+#include "fdbclient/Knobs.h"
 #include "fdbclient/MutationList.h"
+#include "flow/ArgParseUtil.h"
 #include "flow/IRandom.h"
 #include "flow/Trace.h"
 #include "flow/flow.h"
 #include "flow/serialize.h"
-#include "fdbclient/BuildFlags.h"
+
 #include "flow/actorcompiler.h" // has to be last include
 
 #define SevDecodeInfo SevVerbose
@@ -73,11 +77,13 @@ void printDecodeUsage() {
 	             "  --list-only    Print file list and exit.\n"
 	             "  -k KEY_PREFIX  Use the prefix for filtering mutations\n"
 	             "  --hex-prefix   HEX_PREFIX\n"
-	             "                 The prefix specified in HEX format, e.g., \\x05\\x01.\n"
+	             "                 The prefix specified in HEX format, e.g., \"\\\\x05\\\\x01\".\n"
 	             "  --begin-version-filter BEGIN_VERSION\n"
 	             "                 The version range's begin version (inclusive) for filtering.\n"
 	             "  --end-version-filter END_VERSION\n"
 	             "                 The version range's end version (exclusive) for filtering.\n"
+	             "  --knob-KNOBNAME KNOBVALUE\n"
+	             "                 Changes a knob value. KNOBNAME should be lowercase."
 	             "\n";
 	return;
 }
@@ -97,6 +103,8 @@ struct DecodeParams {
 	Version beginVersionFilter = 0;
 	Version endVersionFilter = std::numeric_limits<Version>::max();
 
+	std::vector<std::pair<std::string, std::string>> knobs;
+
 	// Returns if [begin, end) overlap with the filter range
 	bool overlap(Version begin, Version end) const {
 		// Filter [100, 200),  [50,75) [200, 300)
@@ -130,8 +138,39 @@ struct DecodeParams {
 		if (!prefix.empty()) {
 			s.append(", KeyPrefix: ").append(printable(KeyRef(prefix)));
 		}
+		for (const auto& [knob, value] : knobs) {
+			s.append(", KNOB-").append(knob).append(" = ").append(value);
+		}
 		return s;
 	}
+
+	void updateKnobs() {
+		auto& g_knobs = IKnobCollection::getMutableGlobalKnobCollection();
+		for (const auto& [knobName, knobValueString] : knobs) {
+			try {
+				auto knobValue = g_knobs.parseKnobValue(knobName, knobValueString);
+				g_knobs.setKnob(knobName, knobValue);
+			} catch (Error& e) {
+				if (e.code() == error_code_invalid_option_value) {
+					std::cerr << "WARNING: Invalid value '" << knobValueString << "' for knob option '" << knobName
+					          << "'\n";
+					TraceEvent(SevWarnAlways, "InvalidKnobValue")
+					    .detail("Knob", printable(knobName))
+					    .detail("Value", printable(knobValueString));
+				} else {
+					std::cerr << "ERROR: Failed to set knob option '" << knobName << "': " << e.what() << "\n";
+					TraceEvent(SevError, "FailedToSetKnob")
+					    .errorUnsuppressed(e)
+					    .detail("Knob", printable(knobName))
+					    .detail("Value", printable(knobValueString));
+					throw;
+				}
+			}
+		}
+
+		// Reinitialize knobs in order to update knobs that are dependent on explicitly set knobs
+		g_knobs.initialize(Randomize::True, IsSimulated::False);
+	}
 };
 
 // Decode an ASCII string, e.g., "\x15\x1b\x19\x04\xaf\x0c\x28\x0a",
@@ -256,6 +295,16 @@ int parseDecodeCommandLine(DecodeParams* param, CSimpleOpt* args) {
 			param->tlsConfig.blobCredentials.push_back(args->OptionArg());
 			break;
 
+		case OPT_KNOB: {
+			Optional<std::string> knobName = extractPrefixedArgument("--knob", args->OptionSyntax());
+			if (!knobName.present()) {
+				std::cerr << "ERROR: unable to parse knob option '" << args->OptionSyntax() << "'\n";
+				return FDB_EXIT_ERROR;
+			}
+			param->knobs.emplace_back(knobName.get(), args->OptionArg());
+			break;
+		}
+
 #ifndef TLS_DISABLED
 		case TLSConfig::OPT_TLS_PLUGIN:
 			args->OptionArg();
@@ -552,6 +601,9 @@ int main(int argc, char** argv) {
 		StringRef url(param.container_url);
 		setupNetwork(0, UseMetrics::True);
 
+		// Must be called after setupNetwork() to be effective
+		param.updateKnobs();
+
 		TraceEvent::setNetworkThread();
 		openTraceFile(NetworkAddress(), 10 << 20, 500 << 20, param.log_dir, "decode", param.trace_log_group);
 		param.tlsConfig.setupBlobCredentials();

fdbclient/JSONDoc.h

@@ -22,6 +22,7 @@
 
 #include "fdbclient/json_spirit/json_spirit_writer_template.h"
 #include "fdbclient/json_spirit/json_spirit_reader_template.h"
+#include "flow/Error.h"
 
 // JSONDoc is a convenient reader/writer class for manipulating JSON documents using "paths".
 // Access is done using a "path", which is a string of dot-separated