118 lines
5.0 KiB
C++
118 lines
5.0 KiB
C++
/*
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* IDiskQueue.h
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*
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* This source file is part of the FoundationDB open source project
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*
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* Copyright 2013-2018 Apple Inc. and the FoundationDB project authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef FDBSERVER_IDISKQUEUE_H
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#define FDBSERVER_IDISKQUEUE_H
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#pragma once
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#include "fdbclient/FDBTypes.h"
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#include "fdbserver/IKeyValueStore.h"
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enum class CheckHashes {
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NO,
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YES,
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};
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class IDiskQueue : public IClosable {
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public:
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struct location {
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// location is same with seq., specifying the index of the virtualy infinite queue.
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int64_t hi, lo; // hi is always 0, lo is always equal to seq.
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location() : hi(0), lo(0) {}
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location(int64_t lo) : hi(0), lo(lo) {}
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location(int64_t hi, int64_t lo) : hi(hi), lo(lo) {}
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operator std::string() const { return format("%lld.%lld", hi, lo); } // FIXME: Return a 'HumanReadableDescription' instead of std::string, make TraceEvent::detail accept that (for safety)
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template<class Ar>
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void serialize_unversioned(Ar& ar) {
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serializer(ar, hi, lo);
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}
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bool operator < (location const& r) const {
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if (hi<r.hi) return true;
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if (hi>r.hi) return false;
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return lo < r.lo;
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}
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bool operator == (const location& r) const {
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return hi == r.hi && lo == r.lo;
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}
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};
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//! Find the first and last pages in the disk queue, and initialize invariants.
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//!
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//! Most importantly, most invariants only hold after this function returns, and
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//! some functions assert that the IDiskQueue has been initialized.
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//!
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//! \param recoverAt The minimum location from which to start recovery.
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//! \returns True, if DiskQueue is now considered in a recovered state.
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//! False, if the caller should call readNext until recovered is true.
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virtual Future<bool> initializeRecovery(location recoverAt) = 0;
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// Before calling push or commit, the caller *must* perform recovery by calling readNext() until it returns less than the requested number of bytes.
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// Thereafter it may not be called again.
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virtual Future<Standalone<StringRef>> readNext( int bytes ) = 0; // Return the next bytes in the queue (beginning, the first time called, with the first unpopped byte)
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virtual location getNextReadLocation() = 0; // Returns a location >= the location of all bytes previously returned by readNext(), and <= the location of all bytes subsequently returned
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virtual location getNextCommitLocation() = 0; // If commit() were to be called, all buffered writes would be written starting at `location`.
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virtual location getNextPushLocation() = 0; // If push() were to be called, the pushed data would be written starting at `location`.
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virtual Future<Standalone<StringRef>> read( location start, location end, CheckHashes vc ) = 0;
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virtual location push( StringRef contents ) = 0; // Appends the given bytes to the byte stream. Returns a location token representing the *end* of the contents.
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virtual void pop( location upTo ) = 0; // Removes all bytes before the given location token from the byte stream.
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virtual Future<Void> commit() = 0; // returns when all prior pushes and pops are durable. If commit does not return (due to close or a crash), any prefix of the pushed bytes and any prefix of the popped bytes may be durable.
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virtual int getCommitOverhead() = 0; // returns the amount of unused space that would be written by a commit that immediately followed this call
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virtual StorageBytes getStorageBytes() = 0;
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};
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template<>
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struct Traceable<IDiskQueue::location> : std::true_type {
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static std::string toString(const IDiskQueue::location& value) {
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return value;
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}
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};
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// FIXME: One should be able to use SFINAE to choose between serialize and serialize_unversioned.
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template <class Ar> void load( Ar& ar, IDiskQueue::location& loc ) { loc.serialize_unversioned(ar); }
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template <class Ar> void save( Ar& ar, const IDiskQueue::location& loc ) { const_cast<IDiskQueue::location&>(loc).serialize_unversioned(ar); }
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namespace std {
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template<>
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struct numeric_limits<IDiskQueue::location> {
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static IDiskQueue::location max() {
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int64_t max64 = numeric_limits<int64_t>::max();
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return IDiskQueue::location(max64, max64);
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};
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static IDiskQueue::location min() {
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return IDiskQueue::location(0, 0);
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}
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};
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}
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// Specify which hash function to use for checksum of pages in DiskQueue
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enum class DiskQueueVersion : uint16_t {
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V0 = 0, // Use hashlittle
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V1 = 1, // Use crc32, which is faster than hashlittle
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};
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IDiskQueue* openDiskQueue( std::string basename, std::string ext, UID dbgid, DiskQueueVersion diskQueueVersion, int64_t fileSizeWarningLimit = -1); // opens basename+"0."+ext and basename+"1."+ext
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#endif
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