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SERVER-29418 Create a storage-engine agnostic checkpointing thread
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| /** | ||
| * Copyright (C) 2020-present MongoDB, Inc. | ||
| * | ||
| * This program is free software: you can redistribute it and/or modify | ||
| * it under the terms of the Server Side Public License, version 1, | ||
| * as published by MongoDB, Inc. | ||
| * | ||
| * This program is distributed in the hope that it will be useful, | ||
| * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
| * Server Side Public License for more details. | ||
| * | ||
| * You should have received a copy of the Server Side Public License | ||
| * along with this program. If not, see | ||
| * <http://www.mongodb.com/licensing/server-side-public-license>. | ||
| * | ||
| * As a special exception, the copyright holders give permission to link the | ||
| * code of portions of this program with the OpenSSL library under certain | ||
| * conditions as described in each individual source file and distribute | ||
| * linked combinations including the program with the OpenSSL library. You | ||
| * must comply with the Server Side Public License in all respects for | ||
| * all of the code used other than as permitted herein. If you modify file(s) | ||
| * with this exception, you may extend this exception to your version of the | ||
| * file(s), but you are not obligated to do so. If you do not wish to do so, | ||
| * delete this exception statement from your version. If you delete this | ||
| * exception statement from all source files in the program, then also delete | ||
| * it in the license file. | ||
| */ | ||
|
|
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| #define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kStorage | ||
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| #include "mongo/platform/basic.h" | ||
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| #include "mongo/db/storage/checkpointer.h" | ||
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| #include "mongo/db/operation_context.h" | ||
| #include "mongo/db/service_context.h" | ||
| #include "mongo/db/storage/kv/kv_engine.h" | ||
| #include "mongo/logv2/log.h" | ||
| #include "mongo/util/concurrency/idle_thread_block.h" | ||
| #include "mongo/util/fail_point.h" | ||
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| namespace mongo { | ||
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| namespace { | ||
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| const auto getCheckpointer = ServiceContext::declareDecoration<std::unique_ptr<Checkpointer>>(); | ||
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| MONGO_FAIL_POINT_DEFINE(pauseCheckpointThread); | ||
|
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| } // namespace | ||
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| Checkpointer* Checkpointer::get(ServiceContext* serviceCtx) { | ||
| return getCheckpointer(serviceCtx).get(); | ||
| } | ||
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| Checkpointer* Checkpointer::get(OperationContext* opCtx) { | ||
| return get(opCtx->getServiceContext()); | ||
| } | ||
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| void Checkpointer::set(ServiceContext* serviceCtx, std::unique_ptr<Checkpointer> newCheckpointer) { | ||
| auto& checkpointer = getCheckpointer(serviceCtx); | ||
| if (checkpointer) { | ||
| invariant(!checkpointer->running(), | ||
| "Tried to reset the Checkpointer without shutting down the original instance."); | ||
| } | ||
| checkpointer = std::move(newCheckpointer); | ||
| } | ||
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| void Checkpointer::run() { | ||
| ThreadClient tc(name(), getGlobalServiceContext()); | ||
| LOGV2_DEBUG(22307, 1, "Starting thread", "threadName"_attr = name()); | ||
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| while (true) { | ||
| auto opCtx = tc->makeOperationContext(); | ||
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| { | ||
| stdx::unique_lock<Latch> lock(_mutex); | ||
| MONGO_IDLE_THREAD_BLOCK; | ||
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| // Wait for 'storageGlobalParams.checkpointDelaySecs' seconds; or until either shutdown | ||
| // is signaled or a checkpoint is triggered. | ||
| _sleepCV.wait_for(lock, | ||
| stdx::chrono::seconds(static_cast<std::int64_t>( | ||
| storageGlobalParams.checkpointDelaySecs)), | ||
| [&] { return _shuttingDown || _triggerCheckpoint; }); | ||
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| // If the checkpointDelaySecs is set to 0, that means we should skip checkpointing. | ||
| // However, checkpointDelaySecs is adjustable by a runtime server parameter, so we | ||
| // need to wake up to check periodically. The wakeup to check period is arbitrary. | ||
| while (storageGlobalParams.checkpointDelaySecs == 0 && !_shuttingDown && | ||
| !_triggerCheckpoint) { | ||
| _sleepCV.wait_for(lock, stdx::chrono::seconds(static_cast<std::int64_t>(3)), [&] { | ||
| return _shuttingDown || _triggerCheckpoint; | ||
| }); | ||
| } | ||
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| if (_shuttingDown) { | ||
| invariant(!_shutdownReason.isOK()); | ||
| LOGV2_DEBUG(22309, | ||
| 1, | ||
| "Stopping thread", | ||
| "threadName"_attr = name(), | ||
| "reason"_attr = _shutdownReason); | ||
| return; | ||
| } | ||
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| // Clear the trigger so we do not immediately checkpoint again after this. | ||
| _triggerCheckpoint = false; | ||
| } | ||
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| pauseCheckpointThread.pauseWhileSet(); | ||
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| const Date_t startTime = Date_t::now(); | ||
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| // TODO SERVER-50861: Access the storage engine via the ServiceContext. | ||
| _kvEngine->checkpoint(); | ||
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| const auto secondsElapsed = durationCount<Seconds>(Date_t::now() - startTime); | ||
| if (secondsElapsed >= 30) { | ||
| LOGV2_DEBUG(22308, | ||
| 1, | ||
| "Checkpoint was slow to complete", | ||
| "secondsElapsed"_attr = secondsElapsed); | ||
| } | ||
| } | ||
| } | ||
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| void Checkpointer::triggerFirstStableCheckpoint(Timestamp prevStable, | ||
| Timestamp initialData, | ||
| Timestamp currStable) { | ||
| stdx::unique_lock<Latch> lock(_mutex); | ||
| invariant(!_hasTriggeredFirstStableCheckpoint); | ||
| if (prevStable < initialData && currStable >= initialData) { | ||
| LOGV2(22310, | ||
| "Triggering the first stable checkpoint", | ||
| "initialDataTimestamp"_attr = initialData, | ||
| "prevStableTimestamp"_attr = prevStable, | ||
| "currStableTimestamp"_attr = currStable); | ||
| _hasTriggeredFirstStableCheckpoint = true; | ||
| _triggerCheckpoint = true; | ||
| _sleepCV.notify_one(); | ||
| } | ||
| } | ||
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| bool Checkpointer::hasTriggeredFirstStableCheckpoint() { | ||
| stdx::unique_lock<Latch> lock(_mutex); | ||
| return _hasTriggeredFirstStableCheckpoint; | ||
| } | ||
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| void Checkpointer::shutdown(const Status& reason) { | ||
| LOGV2(22322, "Shutting down checkpoint thread"); | ||
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| { | ||
| stdx::unique_lock<Latch> lock(_mutex); | ||
| _shuttingDown = true; | ||
| _shutdownReason = reason; | ||
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| // Wake up the checkpoint thread early, to take a final checkpoint before shutting down, if | ||
| // one has not coincidentally just been taken. | ||
| _sleepCV.notify_one(); | ||
| } | ||
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| wait(); | ||
| LOGV2(22323, "Finished shutting down checkpoint thread"); | ||
| } | ||
|
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||
| } // namespace mongo |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,114 @@ | ||
| /** | ||
| * Copyright (C) 2020-present MongoDB, Inc. | ||
| * | ||
| * This program is free software: you can redistribute it and/or modify | ||
| * it under the terms of the Server Side Public License, version 1, | ||
| * as published by MongoDB, Inc. | ||
| * | ||
| * This program is distributed in the hope that it will be useful, | ||
| * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
| * Server Side Public License for more details. | ||
| * | ||
| * You should have received a copy of the Server Side Public License | ||
| * along with this program. If not, see | ||
| * <http://www.mongodb.com/licensing/server-side-public-license>. | ||
| * | ||
| * As a special exception, the copyright holders give permission to link the | ||
| * code of portions of this program with the OpenSSL library under certain | ||
| * conditions as described in each individual source file and distribute | ||
| * linked combinations including the program with the OpenSSL library. You | ||
| * must comply with the Server Side Public License in all respects for | ||
| * all of the code used other than as permitted herein. If you modify file(s) | ||
| * with this exception, you may extend this exception to your version of the | ||
| * file(s), but you are not obligated to do so. If you do not wish to do so, | ||
| * delete this exception statement from your version. If you delete this | ||
| * exception statement from all source files in the program, then also delete | ||
| * it in the license file. | ||
| */ | ||
|
|
||
| #pragma once | ||
|
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| #include "mongo/platform/mutex.h" | ||
| #include "mongo/stdx/condition_variable.h" | ||
| #include "mongo/util/background.h" | ||
|
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| namespace mongo { | ||
|
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| class KVEngine; | ||
| class OperationContext; | ||
| class ServiceContext; | ||
| class Timestamp; | ||
|
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| class Checkpointer : public BackgroundJob { | ||
| public: | ||
| Checkpointer(KVEngine* kvEngine) | ||
| : BackgroundJob(false /* deleteSelf */), | ||
| _kvEngine(kvEngine), | ||
| _shuttingDown(false), | ||
| _shutdownReason(Status::OK()), | ||
| _hasTriggeredFirstStableCheckpoint(false), | ||
| _triggerCheckpoint(false) {} | ||
|
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| static Checkpointer* get(ServiceContext* serviceCtx); | ||
| static Checkpointer* get(OperationContext* opCtx); | ||
| static void set(ServiceContext* serviceCtx, std::unique_ptr<Checkpointer> newCheckpointer); | ||
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| std::string name() const override { | ||
| return "Checkpointer"; | ||
| } | ||
|
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| /** | ||
| * Starts the checkpoint thread that runs every storageGlobalParams.checkpointDelaySecs seconds. | ||
| */ | ||
| void run() override; | ||
|
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| /** | ||
| * Triggers taking the first stable checkpoint if the stable timestamp has advanced past the | ||
| * initial data timestamp. | ||
| * | ||
| * The checkpoint thread runs automatically every storageGlobalParams.checkpointDelaySecs | ||
| * seconds. This function avoids potentially waiting that full duration for a stable checkpoint, | ||
| * initiating one immediately. | ||
| * | ||
| * Do not call this function if hasTriggeredFirstStableCheckpoint() returns true. | ||
| */ | ||
| void triggerFirstStableCheckpoint(Timestamp prevStable, | ||
| Timestamp initialData, | ||
| Timestamp currStable); | ||
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| /** | ||
| * Returns whether the first stable checkpoint has already been triggered. | ||
| */ | ||
| bool hasTriggeredFirstStableCheckpoint(); | ||
|
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| /** | ||
| * Blocks until the checkpoint thread has been fully shutdown. | ||
| */ | ||
| void shutdown(const Status& reason); | ||
|
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| private: | ||
| // A pointer to the KVEngine is maintained only due to unit testing limitations that don't fully | ||
| // setup the ServiceContext. | ||
| // TODO SERVER-50861: Remove this pointer. | ||
| KVEngine* const _kvEngine; | ||
|
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| // Protects the state below. | ||
| Mutex _mutex = MONGO_MAKE_LATCH("Checkpointer::_mutex"); | ||
|
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| // The checkpoint thread idles on this condition variable for a particular time duration between | ||
| // taking checkpoints. It can be triggered early to expedite either: immediate checkpointing if | ||
| // _triggerCheckpoint is set; or shutdown cleanup if _shuttingDown is set. | ||
| stdx::condition_variable _sleepCV; | ||
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| bool _shuttingDown; | ||
| Status _shutdownReason; | ||
|
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| // This flag ensures the first stable checkpoint is only triggered once. | ||
| bool _hasTriggeredFirstStableCheckpoint; | ||
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| // This flag allows the checkpoint thread to wake up early when _sleepCV is signaled. | ||
| bool _triggerCheckpoint; | ||
| }; | ||
|
|
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| } // namespace mongo |
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