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/**
* Copyright (C) 2014 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* 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 GNU Affero General 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/base/status.h"
#include "mongo/db/repl/replication_executor.h"
#include "mongo/db/repl/scatter_gather_algorithm.h"
namespace mongo {
namespace repl {
class ReplicaSetConfig;
/**
* Quorum checking state machine.
*
* Usage: Construct a QuorumChecker, pass in a pointer to the configuration for which you're
* checking quorum, and the integer index of the member config representing the "executing"
* node. Use ScatterGatherRunner or otherwise execute a scatter-gather procedure as described
* in the class comment for the ScatterGatherAlgorithm class. After
* hasReceivedSufficientResponses() returns true, you may call getFinalStatus() to get the
* result of the quorum check.
*/
class QuorumChecker : public ScatterGatherAlgorithm {
MONGO_DISALLOW_COPYING(QuorumChecker);
public:
/**
* Constructs a QuorumChecker that is used to confirm that sufficient nodes are up to accept
* "rsConfig". "myIndex" is the index of the local node, which is assumed to be up.
*
* "rsConfig" must stay in scope until QuorumChecker's destructor completes.
*/
QuorumChecker(const ReplicaSetConfig* rsConfig, int myIndex);
virtual ~QuorumChecker();
virtual std::vector<RemoteCommandRequest> getRequests() const;
virtual void processResponse(
const RemoteCommandRequest& request,
const ResponseStatus& response);
virtual bool hasReceivedSufficientResponses() const;
Status getFinalStatus() const { return _finalStatus; }
private:
/**
* Callback that executes after _haveReceivedSufficientReplies() becomes true.
*
* Computes the quorum result based on responses received so far, stores it into
* _finalStatus, and enables QuorumChecker::run() to return.
*/
void _onQuorumCheckComplete();
/**
* Updates the QuorumChecker state based on the data from a single heartbeat response.
*/
void _tabulateHeartbeatResponse(const RemoteCommandRequest& request,
const ResponseStatus& response);
// Pointer to the replica set configuration for which we're checking quorum.
const ReplicaSetConfig* const _rsConfig;
// Index of the local node's member configuration in _rsConfig.
const int _myIndex;
// List of voting nodes that have responded affirmatively.
std::vector<HostAndPort> _voters;
// List of nodes with bad responses and the bad response status they returned.
std::vector<std::pair<HostAndPort, Status> > _badResponses;
// Total number of responses and timeouts processed.
int _numResponses;
// Number of electable nodes that have responded affirmatively.
int _numElectable;
// Set to a non-OK status if a response from a remote node indicates
// that the quorum check should definitely fail, such as because of
// a replica set name mismatch.
Status _vetoStatus;
// Final status of the quorum check, returned by run().
Status _finalStatus;
};
/**
* Performs a quorum call to determine if a sufficient number of nodes are up
* to initiate a replica set with configuration "rsConfig".
*
* "myIndex" is the index of this node's member configuration in "rsConfig".
* "executor" is the event loop in which to schedule network/aysnchronous processing.
*
* For purposes of initiate, a quorum is only met if all of the following conditions
* are met:
* - All nodes respond.
* - No nodes other than the node running the quorum check have data.
* - No nodes are already joined to a replica set.
* - No node reports a replica set name other than the one in "rsConfig".
*/
Status checkQuorumForInitiate(ReplicationExecutor* executor,
const ReplicaSetConfig& rsConfig,
const int myIndex);
/**
* Performs a quorum call to determine if a sufficient number of nodes are up
* to replace the current replica set configuration with "rsConfig".
*
* "myIndex" is the index of this node's member configuration in "rsConfig".
* "executor" is the event loop in which to schedule network/aysnchronous processing.
*
* For purposes of reconfig, a quorum is only met if all of the following conditions
* are met:
* - A majority of voting nodes respond.
* - At least one electable node responds.
* - No responding node reports a replica set name other than the one in "rsConfig".
* - All responding nodes report a config version less than the one in "rsConfig".
*/
Status checkQuorumForReconfig(ReplicationExecutor* executor,
const ReplicaSetConfig& rsConfig,
const int myIndex);
} // namespace repl
} // namespace mongo
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