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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 <boost/scoped_ptr.hpp>
#include <vector>
#include "mongo/base/disallow_copying.h"
#include "mongo/bson/optime.h"
#include "mongo/db/repl/replica_set_config.h"
#include "mongo/db/repl/replication_executor.h"
#include "mongo/db/repl/scatter_gather_algorithm.h"
namespace mongo {
class Status;
namespace repl {
class ReplicaSetConfig;
class ScatterGatherRunner;
class FreshnessChecker {
MONGO_DISALLOW_COPYING(FreshnessChecker);
public:
enum ElectionAbortReason {
None = 0,
FresherNodeFound, // Freshness check found fresher node
FreshnessTie, // Freshness check resulted in one or more nodes with our lastAppliedOpTime
QuorumUnavailable, // Not enough up voters
QuorumUnreachable // Too many failed voter responses
};
class Algorithm : public ScatterGatherAlgorithm {
public:
Algorithm(OpTime lastOpTimeApplied,
const ReplicaSetConfig& rsConfig,
int selfIndex,
const std::vector<HostAndPort>& targets);
virtual ~Algorithm();
virtual std::vector<ReplicationExecutor::RemoteCommandRequest> getRequests() const;
virtual void processResponse(
const ReplicationExecutor::RemoteCommandRequest& request,
const ResponseStatus& response);
virtual bool hasReceivedSufficientResponses() const;
ElectionAbortReason shouldAbortElection() const;
private:
// Returns true if the number of failed votes is over _losableVotes()
bool hadTooManyFailedVoterResponses() const;
// Returns true if the member, by host and port, has a vote.
bool _isVotingMember(const HostAndPort host) const;
// Number of responses received so far.
int _responsesProcessed;
// Number of failed voter responses so far.
int _failedVoterResponses;
// Last OpTime applied by the caller; used in the Fresh command
const OpTime _lastOpTimeApplied;
// Config to use for this check
const ReplicaSetConfig _rsConfig;
// Our index position in _rsConfig
const int _selfIndex;
// The UP members we are checking
const std::vector<HostAndPort> _targets;
// Number of voting targets
int _votingTargets;
// Number of voting nodes which can error
int _losableVoters;
// 1 if I have a vote, otherwise 0
int _myVote;
// Reason to abort, start with None
ElectionAbortReason _abortReason;
};
FreshnessChecker();
virtual ~FreshnessChecker();
/**
* Begins the process of sending replSetFresh commands to all non-DOWN nodes
* in currentConfig, with the intention of determining whether the current node
* is freshest.
* evh can be used to schedule a callback when the process is complete.
* This function must be run in the executor, as it must be synchronous with the command
* callbacks that it schedules.
* If this function returns Status::OK(), evh is then guaranteed to be signaled.
**/
StatusWith<ReplicationExecutor::EventHandle> start(
ReplicationExecutor* executor,
const OpTime& lastOpTimeApplied,
const ReplicaSetConfig& currentConfig,
int selfIndex,
const std::vector<HostAndPort>& targets,
const stdx::function<void ()>& onCompletion = stdx::function<void ()>());
/**
* Informs the freshness checker to cancel further processing. The "executor"
* argument must point to the same executor passed to "start()".
*
* Like start(), this method must run in the executor context.
*/
void cancel(ReplicationExecutor* executor);
/**
* Returns true if cancel() was called on this instance.
*/
bool isCanceled() const { return _isCanceled; }
/**
* 'None' if the election should continue, otherwise the reason to abort
*/
ElectionAbortReason shouldAbortElection() const;
/**
* Returns the config version supplied in the config when start() was called.
* Useful for determining if the the config version has changed.
*/
long long getOriginalConfigVersion() const;
private:
boost::scoped_ptr<Algorithm> _algorithm;
boost::scoped_ptr<ScatterGatherRunner> _runner;
long long _originalConfigVersion;
bool _isCanceled;
};
} // namespace repl
} // namespace mongo
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