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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.
*/
#pragma once
#include "mongo/db/repl/oplog.h"
#include "mongo/db/repl/oplog_entry.h"
#include "mongo/db/s/resharding/donor_oplog_id_gen.h"
#include "mongo/db/s/resharding/resharding_donor_oplog_iterator.h"
#include "mongo/db/s/resharding/resharding_oplog_application.h"
#include "mongo/db/s/resharding/resharding_oplog_applier_progress_gen.h"
#include "mongo/db/s/resharding/resharding_oplog_batch_preparer.h"
#include "mongo/executor/task_executor.h"
#include "mongo/s/chunk_manager.h"
#include "mongo/util/future.h"
namespace mongo {
class ServiceContext;
class ThreadPool;
/**
* Applies oplog entries from a specific donor for resharding.
*
* This is not thread safe.
*/
class ReshardingOplogApplier {
public:
ReshardingOplogApplier(ServiceContext* service,
ReshardingSourceId sourceId,
NamespaceString oplogNs,
NamespaceString nsBeingResharded,
UUID collUUIDBeingResharded,
std::vector<NamespaceString> allStashNss,
size_t myStashIdx,
Timestamp reshardingCloneFinishedTs,
std::unique_ptr<ReshardingDonorOplogIteratorInterface> oplogIterator,
const ChunkManager& sourceChunkMgr,
std::shared_ptr<executor::TaskExecutor> executor,
ThreadPool* writerPool);
/**
* Applies oplog from the iterator until it has at least applied an oplog entry with timestamp
* greater than or equal to reshardingCloneFinishedTs.
* It is undefined to call applyUntilCloneFinishedTs more than once.
*/
ExecutorFuture<void> applyUntilCloneFinishedTs();
/**
* Applies oplog from the iterator until it is exhausted or hits an error. It is an error to
* call this without calling applyUntilCloneFinishedTs first.
*
* It is an error to call this when applyUntilCloneFinishedTs future returns an error.
* It is undefined to call applyUntilDone more than once.
*/
ExecutorFuture<void> applyUntilDone();
static boost::optional<ReshardingOplogApplierProgress> checkStoredProgress(
OperationContext* opCtx, const ReshardingSourceId& id);
static NamespaceString ensureStashCollectionExists(OperationContext* opCtx,
const UUID& existingUUID,
const ShardId& donorShardId,
const CollectionOptions& options);
private:
using OplogBatch = std::vector<repl::OplogEntry>;
enum class Stage { kStarted, kErrorOccurred, kReachedCloningTS, kFinished };
/**
* Returns a future that becomes ready when the next batch of oplog entries have been collected
* and applied.
*/
ExecutorFuture<void> _scheduleNextBatch();
/**
* Setup the worker threads to apply the ops in the current buffer in parallel. Waits for all
* worker threads to finish (even when some of them finished early due to an error).
*/
Future<void> _applyBatch(OperationContext* opCtx, bool isForSessionApplication);
/**
* Apply a slice of oplog entries from the current batch for a worker thread.
*/
Status _applyOplogBatchPerWorker(std::vector<const repl::OplogEntry*>* ops);
/**
* Apply the oplog entries.
*/
Status _applyOplogEntry(OperationContext* opCtx, const repl::OplogEntry& op);
/**
* Record results from a writer vector for the current batch being applied.
*/
void _onWriterVectorDone(Status status);
/**
* Takes note that an error occurred and set the appropriate promise.
*
* Note: currently only supports being called on context where no other thread can modify
* _stage variable.
*/
Status _onError(Status status);
/**
* Records the progress made by this applier to storage. Returns the timestamp of the progress
* recorded.
*/
Timestamp _clearAppliedOpsAndStoreProgress(OperationContext* opCtx);
static constexpr auto kClientName = "ReshardingOplogApplier"_sd;
// Identifier for the oplog source.
const ReshardingSourceId _sourceId;
// Namespace that contains the oplog from a source shard that this is going to apply.
const NamespaceString _oplogNs;
// Namespace of the real collection being resharded.
const NamespaceString _nsBeingResharded;
// UUID of the real collection being resharded.
const UUID _uuidBeingResharded;
// Namespace of collection where operations are going to get applied.
const NamespaceString _outputNs;
// The timestamp of the latest oplog entry on the source shard at the time when resharding
// finished cloning from it.
const Timestamp _reshardingCloneFinishedTs;
const ReshardingOplogBatchPreparer _batchPreparer;
// Actually applies the ops, using special rules that apply only to resharding. Only used when
// the 'useReshardingOplogApplicationRules' server parameter is set to true.
ReshardingOplogApplicationRules _applicationRules;
Mutex _mutex = MONGO_MAKE_LATCH("ReshardingOplogApplier::_mutex");
// Member variable concurrency access rules:
//
// M - Mutex protected. Must hold _mutex when accessing
// R - Read relaxed. Can read freely without holding mutex because there are no case where
// more than one thread will modify it concurrently while being read.
// S - Special case. Manages it's own concurrency. Can access without holding mutex.
// (S)
ServiceContext* _service;
// (S)
std::shared_ptr<executor::TaskExecutor> _executor;
// (S) Thread pool for replication oplog applier;
ThreadPool* _writerPool;
// (R) Buffer for the current batch of oplog entries to apply.
OplogBatch _currentBatchToApply;
// (R) Buffer for internally generated oplog entries that needs to be processed for this batch.
std::list<repl::OplogEntry> _currentDerivedOps;
// (R) A temporary scratch pad that contains pointers to oplog entries in _currentBatchToApply
// that is used by the writer vector when applying oplog in parallel.
std::vector<std::vector<const repl::OplogEntry*>> _currentWriterVectors;
// (S) The promise to signal that a batch has finished applying.
Promise<void> _currentApplyBatchPromise;
// (M) Keeps track of how many writer vectors has been applied.
int _remainingWritersToWait{0};
// (M) Keeps track of the status from writer vectors. Will only keep one error if there are
// multiple occurrances.
Status _currentBatchConsolidatedStatus{Status::OK()};
// (R) The source of the oplog entries to be applied.
std::unique_ptr<ReshardingDonorOplogIteratorInterface> _oplogIter;
// (R) Tracks the current stage of this applier.
Stage _stage{Stage::kStarted};
};
} // namespace mongo
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