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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
namespace mongo {
class OperationContext;
class ServiceContext;
/**
* Used to detect when a shard's shardIdentity document has been rolled back. Since rolling back
* the shardIdentity document is illegal (as we can't clear the in-memory state associated with it),
* we force the mongod to shut down if it happens. We detect shardIdentity rollback by checking in
* the OpObserver for that document to be deleted. We can't shut down right at that moment,
* however, as doing so would interrupt the rollback process and leave the document in place for
* when the server is restarted. Instead, when we detect the shardIdentity document being deleted,
* we call recordThatRollbackHappened() on this class, which records the fact that the shardIdentity
* document was deleted as part of the rollback, and then when we exit rollback we check
* didRollbackHappen() and shut down if so.
*
* No concurrency control is needed in this class as recordThatRollbackHappened can only happen in
* an OpObserver detecting that the document was deleted, and didRollbackHappen is only called on
* exiting rollback, and there can only be one of those things happening at any given time.
*/
class ShardIdentityRollbackNotifier {
ShardIdentityRollbackNotifier(const ShardIdentityRollbackNotifier&) = delete;
ShardIdentityRollbackNotifier& operator=(const ShardIdentityRollbackNotifier&) = delete;
public:
ShardIdentityRollbackNotifier();
/**
* Retrieves the ShardIdentityRollbackNotifier associated with the specified service context.
*/
static ShardIdentityRollbackNotifier* get(OperationContext* opCtx);
static ShardIdentityRollbackNotifier* get(ServiceContext* opCtx);
/**
* Records the fact that the shardIdentity document was rolled back.
*/
void recordThatRollbackHappened() {
_rollbackHappened = true;
}
/**
* Checks whether the shardIdentity document was rolled back.
*/
bool didRollbackHappen() {
return _rollbackHappened;
}
private:
// Whether or not a rollback of the shardIdentity document has been detected.
// No concurrency control necessary since this is only consulted during
bool _rollbackHappened = false;
};
} // namespace mongo
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