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/**
* Copyright (C) 2019-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_buffer.h"
#include "mongo/db/repl/oplog_entry.h"
#include "mongo/db/repl/storage_interface.h"
#include "mongo/stdx/thread.h"
#include "mongo/util/fail_point.h"
#include "mongo/util/invariant.h"
namespace mongo {
namespace repl {
class OplogApplier;
/**
* Stores a batch of oplog entries for oplog application.
*/
class OplogBatch {
public:
explicit OplogBatch(std::size_t batchLimitOps) {
_batch.reserve(batchLimitOps);
}
bool empty() const {
return _batch.empty();
}
const OplogEntry& front() const {
invariant(!_batch.empty());
return _batch.front();
}
const OplogEntry& back() const {
invariant(!_batch.empty());
return _batch.back();
}
const std::vector<OplogEntry>& getBatch() const {
return _batch;
}
void emplace_back(OplogEntry oplog) {
invariant(!_mustShutdown);
_batch.emplace_back(std::move(oplog));
}
void pop_back() {
_batch.pop_back();
}
/**
* A batch with this set indicates that the upstream stages of the pipeline are shutdown and
* no more batches will be coming.
*
* This can only happen with empty batches.
*/
bool mustShutdown() const {
return _mustShutdown;
}
void setMustShutdownFlag() {
invariant(empty());
_mustShutdown = true;
}
/**
* Passes the term when the buffer is exhausted to a higher level in case the node has stepped
* down and then stepped up again. See its caller for more context.
*/
boost::optional<long long> termWhenExhausted() const {
return _termWhenExhausted;
}
void setTermWhenExhausted(long long term) {
invariant(empty());
_termWhenExhausted = term;
}
/**
* Leaves this object in an unspecified state. Only assignment and destruction are valid.
*/
std::vector<OplogEntry> releaseBatch() {
return std::move(_batch);
}
private:
std::vector<OplogEntry> _batch;
bool _mustShutdown = false;
boost::optional<long long> _termWhenExhausted;
};
/**
* Consumes batches of oplog entries from the OplogBuffer to give to the oplog applier, freeing
* up space for more operations to be fetched from a sync source and allocated onto the OplogBuffer.
*/
class OplogBatcher {
OplogBatcher(const OplogBatcher&) = delete;
OplogBatcher& operator=(const OplogBatcher&) = delete;
public:
/**
* Controls what can popped from the oplog buffer into a single batch of operations that can be
* applied using OplogApplier::applyOplogBatch().
*/
class BatchLimits {
public:
size_t bytes = 0;
size_t ops = 0;
// If provided, the batch will not include any operations with timestamps after this point.
// This is intended for implementing slaveDelay, so it should be some number of seconds
// before now.
boost::optional<Date_t> slaveDelayLatestTimestamp = {};
// If non-null, the batch will include operations with timestamps either
// before-and-including this point or after it, not both.
Timestamp forceBatchBoundaryAfter;
};
/**
* Constructs an OplogBatcher
*/
OplogBatcher(OplogApplier* oplogApplier, OplogBuffer* oplogBuffer);
virtual ~OplogBatcher();
/**
* Returns the batch of oplog entries and clears _ops so the batcher can store a new batch.
*/
OplogBatch getNextBatch(Seconds maxWaitTime);
/**
* Starts up a thread to continuously pull from the OplogBuffer into the OplogBatcher's oplog
* batch.
*/
void startup(StorageInterface* storageInterface);
/**
* Shuts down the thread that pulls from the OplogBuffer to the oplog batch.
*/
void shutdown();
/**
* Returns a new batch of ops to apply.
* A batch may consist of:
* at most "BatchLimits::ops" OplogEntries
* at most "BatchLimits::bytes" worth of OplogEntries
* only OplogEntries from before the "BatchLimits::slaveDelayLatestTimestamp" point
* a single command OplogEntry (excluding applyOps, which are grouped with CRUD ops)
*/
StatusWith<std::vector<OplogEntry>> getNextApplierBatch(OperationContext* opCtx,
const BatchLimits& batchLimits);
/**
* Helper method indicating that this oplog entry must be in a batch of its own.
*/
static bool mustProcessIndividually(const OplogEntry& entry);
/**
* Returns the number of logical operations represented by an oplog entry.
* This is usually one but may be greater than one in certain cases, such as in a
* commitTransaction command.
*/
static std::size_t getOpCount(const OplogEntry& entry);
private:
/**
* If slaveDelay is enabled, this function calculates the most recent timestamp of any oplog
* entries that can be be returned in a batch.
*/
boost::optional<Date_t> _calculateSlaveDelayLatestTimestamp();
/**
* Pops the operation at the front of the OplogBuffer.
*/
void _consume(OperationContext* opCtx, OplogBuffer* oplogBuffer);
void _run(StorageInterface* storageInterface);
OplogApplier* _oplogApplier;
OplogBuffer* const _oplogBuffer;
Mutex _mutex = MONGO_MAKE_LATCH("OplogBatcher::_mutex");
stdx::condition_variable _cv;
/**
* The latest batch of oplog entries ready for the applier.
*/
OplogBatch _ops;
std::unique_ptr<stdx::thread> _thread;
};
/**
* Returns maximum number of operations in each batch that can be applied using
* applyOplogBatch().
*/
std::size_t getBatchLimitOplogEntries();
/**
* Calculates batch limit size (in bytes) using the maximum capped collection size of the oplog
* size. Must not be called from within a WriteUnitOfWork.
* Batches are limited to 10% of the oplog.
*/
std::size_t getBatchLimitOplogBytes(OperationContext* opCtx, StorageInterface* storageInterface);
} // namespace repl
} // namespace mongo
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