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/**
* Copyright (C) 2018-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 <cstddef>
#include "mongo/base/status_with.h"
#include "mongo/bson/timestamp.h"
#include "mongo/client/fetcher.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/repl/abstract_oplog_fetcher.h"
#include "mongo/db/repl/data_replicator_external_state.h"
#include "mongo/db/repl/repl_set_config.h"
#include "mongo/stdx/functional.h"
#include "mongo/util/fail_point_service.h"
namespace mongo {
namespace repl {
MONGO_FAIL_POINT_DECLARE(stopReplProducer);
/**
* The oplog fetcher, once started, reads operations from a remote oplog using a tailable cursor.
*
* The initial find command is generated from last fetched optime and may contain the current term
* depending on the replica set config provided.
*
* Forwards metadata in each find/getMore response to the data replicator external state.
*
* Performs additional validation on first batch of operations returned from the query to ensure we
* are able to continue from our last known fetched operation.
*
* Validates each batch of operations.
*
* Pushes operations from each batch of operations onto a buffer using the "enqueueDocumentsFn"
* function.
*
* Issues a getMore command after successfully processing each batch of operations.
*
* When there is an error or when it is not possible to issue another getMore request, calls
* "onShutdownCallbackFn" to signal the end of processing.
*
* This class subclasses AbstractOplogFetcher which takes care of scheduling the Fetcher and
* `getMore` commands, and handles restarting on errors.
*/
class OplogFetcher : public AbstractOplogFetcher {
OplogFetcher(const OplogFetcher&) = delete;
OplogFetcher& operator=(const OplogFetcher&) = delete;
public:
static Seconds kDefaultProtocolZeroAwaitDataTimeout;
/**
* Statistics on current batch of operations returned by the fetcher.
*/
struct DocumentsInfo {
size_t networkDocumentCount = 0;
size_t networkDocumentBytes = 0;
size_t toApplyDocumentCount = 0;
size_t toApplyDocumentBytes = 0;
OpTime lastDocument = OpTime();
};
/**
* An enum that indicates if we want to skip the first document during oplog fetching or not.
* Currently, the only time we don't want to skip the first document is during initial sync
* if the sync source has a valid oldest active transaction optime, as we need to include
* the corresponding oplog entry when applying.
*/
enum class StartingPoint { kSkipFirstDoc, kEnqueueFirstDoc };
/**
* Type of function that accepts a pair of iterators into a range of operations
* within the current batch of results and copies the operations into
* a buffer to be consumed by the next stage of the replication process.
*
* Additional information on the operations is provided in a DocumentsInfo
* struct.
*/
using EnqueueDocumentsFn = stdx::function<Status(Fetcher::Documents::const_iterator begin,
Fetcher::Documents::const_iterator end,
const DocumentsInfo& info)>;
/**
* Validates documents in current batch of results returned from tailing the remote oplog.
* 'first' should be set to true if this set of documents is the first batch returned from the
* query.
* On success, returns statistics on operations.
*/
static StatusWith<DocumentsInfo> validateDocuments(
const Fetcher::Documents& documents,
bool first,
Timestamp lastTS,
StartingPoint startingPoint = StartingPoint::kSkipFirstDoc);
/**
* Invariants if validation fails on any of the provided arguments.
*/
OplogFetcher(executor::TaskExecutor* executor,
OpTime lastFetched,
HostAndPort source,
NamespaceString nss,
ReplSetConfig config,
std::size_t maxFetcherRestarts,
int requiredRBID,
bool requireFresherSyncSource,
DataReplicatorExternalState* dataReplicatorExternalState,
EnqueueDocumentsFn enqueueDocumentsFn,
OnShutdownCallbackFn onShutdownCallbackFn,
const int batchSize,
StartingPoint startingPoint = StartingPoint::kSkipFirstDoc);
virtual ~OplogFetcher();
// ================== Test support API ===================
/**
* Returns metadata object sent in remote commands.
*/
BSONObj getMetadataObject_forTest() const;
/**
* Returns timeout for remote commands to complete.
*/
Milliseconds getRemoteCommandTimeout_forTest() const;
/**
* Returns the await data timeout used for the "maxTimeMS" field in getMore command requests.
*/
Milliseconds getAwaitDataTimeout_forTest() const;
private:
BSONObj _makeFindCommandObject(const NamespaceString& nss,
OpTime lastOpTimeFetched,
Milliseconds findMaxTime) const override;
BSONObj _makeMetadataObject() const override;
Milliseconds _getGetMoreMaxTime() const override;
/**
* This function is run by the AbstractOplogFetcher on a successful batch of oplog entries.
*/
StatusWith<BSONObj> _onSuccessfulBatch(const Fetcher::QueryResponse& queryResponse) override;
// The metadata object sent with the Fetcher queries.
const BSONObj _metadataObject;
// Rollback ID that the sync source is required to have after the first batch.
int _requiredRBID;
// A boolean indicating whether we should error if the sync source is not ahead of our initial
// last fetched OpTime on the first batch. Most of the time this should be set to true,
// but there are certain special cases, namely during initial sync, where it's acceptable for
// our sync source to have no ops newer than _lastFetched.
bool _requireFresherSyncSource;
DataReplicatorExternalState* const _dataReplicatorExternalState;
const EnqueueDocumentsFn _enqueueDocumentsFn;
const Milliseconds _awaitDataTimeout;
const int _batchSize;
// Indicates if we want to skip the first document during oplog fetching or not.
StartingPoint _startingPoint;
};
} // namespace repl
} // namespace mongo
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