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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 <boost/optional.hpp>
#include "mongo/base/status_with.h"
#include "mongo/client/dbclient_base.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/pipeline/expression_context.h"
#include "mongo/db/s/resharding/donor_oplog_id_gen.h"
#include "mongo/db/service_context.h"
#include "mongo/s/shard_id.h"
#include "mongo/util/background.h"
#include "mongo/util/uuid.h"
namespace mongo {
class ReshardingOplogFetcher {
public:
ReshardingOplogFetcher(UUID reshardingUUID,
UUID collUUID,
ReshardingDonorOplogId startAt,
ShardId donorShard,
ShardId recipientShard,
bool doesDonorOwnMinKeyChunk,
NamespaceString toWriteInto);
/**
* Schedules a task that will do the following:
*
* - Find a valid connection to fetch oplog entries from.
* - Send an aggregation request + getMores until either:
* -- The "final resharding" oplog entry is found.
* -- An interruption occurs.
* -- A different error occurs.
*
* In the first two circumstances, the task will return. In the last circumstance, the task will
* be rescheduled in a way that resumes where it had left off from.
*/
void schedule(executor::TaskExecutor* exector);
/**
* Given a connection, fetches and copies oplog entries until reaching an error, or coming
* across a sentinel finish oplog entry. Throws if there's more oplog entries to be copied.
*/
void consume(DBClientBase* conn);
/**
* Kill the underlying client the BackgroundJob is using to expedite cleaning up resources when
* the output is no longer necessary. The underlying `toWriteInto` collection is left intact,
* though likely incomplete.
*/
void setKilled();
/**
* Returns boost::none if the last oplog entry to be copied is found. Otherwise returns the
* ReshardingDonorOplogId to resume querying from.
*
* Issues an aggregation to `DBClientBase`s starting at `startAfter` and copies the entries
* relevant to `recipientShard` into `toWriteInto`. Control is returned when the aggregation
* cursor is exhausted.
*
* Returns an identifier for the last oplog-ish document written to `toWriteInto`.
*
* This method throws.
*
* TODO SERVER-51245 Replace `DBClientBase` with a `Shard`. Right now `Shard` does not do things
* like perform aggregate commands nor does it expose a cursor/stream interface. However, using
* a `Shard` object will provide critical behavior such as advancing logical clock values on a
* response and targetting a node to send the aggregation command to.
*/
boost::optional<ReshardingDonorOplogId> iterate(OperationContext* opCtx,
DBClientBase* conn,
boost::intrusive_ptr<ExpressionContext> expCtx,
ReshardingDonorOplogId startAfter,
UUID collUUID,
const ShardId& recipientShard,
bool doesDonorOwnMinKeyChunk,
NamespaceString toWriteInto);
int getNumOplogEntriesCopied() {
return _numOplogEntriesCopied;
}
private:
/**
* Returns true if there's more work to do and the task should be rescheduled.
*/
bool _runTask();
const UUID _reshardingUUID;
const UUID _collUUID;
ReshardingDonorOplogId _startAt;
const ShardId _donorShard;
const ShardId _recipientShard;
const bool _doesDonorOwnMinKeyChunk;
const NamespaceString _toWriteInto;
ServiceContext::UniqueClient _client;
AtomicWord<bool> _isAlive{true};
int _numOplogEntriesCopied = 0;
};
} // namespace mongo
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