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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 <memory>
#include <string>
#include "mongo/base/status_with.h"
#include "mongo/bson/bsonobj.h"
#include "mongo/db/repl/oplog_entry.h"
#include "mongo/db/s/migration_session_id.h"
#include "mongo/db/shard_id.h"
#include "mongo/platform/mutex.h"
#include "mongo/stdx/condition_variable.h"
#include "mongo/stdx/thread.h"
#include "mongo/util/cancellation.h"
#include "mongo/util/concurrency/with_lock.h"
namespace mongo {
class ConnectionString;
class ServiceContext;
class OperationContext;
/**
* Provides infrastructure for retrieving session information that needs to be migrated from
* the source migration shard.
*/
class SessionCatalogMigrationDestination {
SessionCatalogMigrationDestination(const SessionCatalogMigrationDestination&) = delete;
SessionCatalogMigrationDestination& operator=(const SessionCatalogMigrationDestination&) =
delete;
public:
enum class State {
NotStarted,
Migrating,
ReadyToCommit,
Committing,
ErrorOccurred,
Done,
};
struct ProcessOplogResult {
LogicalSessionId sessionId;
TxnNumber txnNum{kUninitializedTxnNumber};
repl::OpTime oplogTime;
bool isPrePostImage = false;
};
SessionCatalogMigrationDestination(NamespaceString nss,
ShardId fromShard,
MigrationSessionId migrationSessionId,
CancellationToken cancellationToken);
~SessionCatalogMigrationDestination();
/**
* Spawns a separate thread to initiate the session info transfer to this shard.
*/
void start(ServiceContext* service);
/**
* Signals to this object that the source shard will no longer create generate new
* session info to transfer. In other words, once the source shard returns an empty
* result for session info to transfer after this call, it is safe for this to stop.
*/
void finish();
/**
* Joins the spawned thread called by start(). Should only be called after finish()
* was called.
*/
void join();
/**
* Forces this into an error state which will also stop session transfer thread.
*/
void forceFail(StringData errMsg);
/**
* Returns the current state.
*/
State getState();
/**
* Returns the error message stored. This is only valid when getState() == ErrorOccurred.
*/
std::string getErrMsg();
/**
* Returns the number of session oplog entries processed by the _processSessionOplog() method
*/
long long getSessionOplogEntriesMigrated();
private:
void _retrieveSessionStateFromSource(ServiceContext* service);
ProcessOplogResult _processSessionOplog(const BSONObj& oplogBSON,
const ProcessOplogResult& lastResult,
ServiceContext* serviceContext,
CancellationToken cancellationToken);
void _errorOccurred(StringData errMsg);
const NamespaceString _nss;
const ShardId _fromShard;
const MigrationSessionId _migrationSessionId;
const CancellationToken _cancellationToken;
stdx::thread _thread;
// Protects _state and _errMsg.
Mutex _mutex = MONGO_MAKE_LATCH("SessionCatalogMigrationDestination::_mutex");
State _state = State::NotStarted;
std::string _errMsg; // valid only if _state == ErrorOccurred.
// The number of session oplog entries processed. This is not always equal to the number of
// session oplog entries comitted because entries may have been processed but not committed
AtomicWord<long long> _sessionOplogEntriesMigrated{0};
};
} // namespace mongo
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