/**
* Copyright (C) 2016 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 .
*
* 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
#include "mongo/base/status.h"
#include "mongo/base/status_with.h"
#include "mongo/client/fetcher.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/repl/optime.h"
#include "mongo/executor/task_executor.h"
#include "mongo/stdx/condition_variable.h"
#include "mongo/stdx/functional.h"
#include "mongo/stdx/mutex.h"
#include "mongo/util/net/hostandport.h"
#include "mongo/util/time_support.h"
namespace mongo {
class OperationContext;
class Status;
class OperationContext;
namespace repl {
class SyncSourceSelector;
/**
* SyncSourceResolverResponse contains the result from running SyncSourceResolver. This result will
* indicate one of the following:
* 1. A new sync source was selected. isOK() will return true and getSyncSource() will
* return the HostAndPort of the new sync source.
* 2. No sync source was selected. isOK() will return true and getSyncSource() will return
* an empty HostAndPort.
* 3. All potential sync sources are too fresh. isOK() will return false and
* syncSourceStatus will be ErrorCodes::OplogStartMissing and earliestOpTimeSeen will
* contain a new MinValid boundry. getSyncSource() is not valid to call in this state.
*/
struct SyncSourceResolverResponse {
// Contains the new syncSource if syncSourceStatus is OK and the HostAndPort is not empty.
StatusWith syncSourceStatus = {ErrorCodes::BadValue, "status not populated"};
// Contains the new MinValid boundry if syncSourceStatus is ErrorCodes::OplogStartMissing.
OpTime earliestOpTimeSeen;
// Rollback ID of the selected sync source.
// The rbid is fetched before the required optime so callers can be sure that as long as the
// rbid is the same, the required optime is still present.
int rbid;
bool isOK() {
return syncSourceStatus.isOK();
}
HostAndPort getSyncSource() {
invariant(syncSourceStatus.isOK());
return syncSourceStatus.getValue();
}
};
/**
* Supplies a sync source to Fetcher, Rollback and Reporter.
* Obtains sync source candidates to probe from SyncSourceSelector.
* Each instance is created as needed whenever a new sync source is required and
* is meant to be discarded after the sync source resolution is finished - 'onCompletion'
* callback is invoked with the results contained in SyncSourceResolverResponse.
*/
class SyncSourceResolver {
public:
static const NamespaceString kLocalOplogNss;
static const Seconds kFetcherTimeout;
static const Seconds kFetcherErrorBlacklistDuration;
static const Seconds kOplogEmptyBlacklistDuration;
static const Seconds kFirstOplogEntryEmptyBlacklistDuration;
static const Seconds kFirstOplogEntryNullTimestampBlacklistDuration;
static const Minutes kTooStaleBlacklistDuration;
static const Seconds kNoRequiredOpTimeBlacklistDuration;
/**
* Callback function to report final status of resolving sync source.
*/
typedef stdx::function OnCompletionFn;
SyncSourceResolver(executor::TaskExecutor* taskExecutor,
SyncSourceSelector* syncSourceSelector,
const OpTime& lastOpTimeFetched,
const OpTime& requiredOpTime,
const OnCompletionFn& onCompletion);
virtual ~SyncSourceResolver();
/**
* Returns true if we are currently probing sync source candidates.
*/
bool isActive() const;
/**
* Starts probing sync source candidates returned by the sync source selector.
*/
Status startup();
/**
* Cancels all remote commands.
*/
void shutdown();
/**
* Block until inactive.
*/
void join();
private:
bool _isActive_inlock() const;
bool _isShuttingDown() const;
/**
* Returns new sync source from selector.
*/
StatusWith _chooseNewSyncSource();
/**
* Creates fetcher to read the first oplog entry on sync source.
*/
std::unique_ptr _makeFirstOplogEntryFetcher(HostAndPort candidate,
OpTime earliestOpTimeSeen);
/**
* Creates fetcher to check the remote oplog for '_requiredOpTime'.
*/
std::unique_ptr _makeRequiredOpTimeFetcher(HostAndPort candidate,
OpTime earliestOpTimeSeen);
/**
* Schedules fetcher to read oplog on sync source.
* Saves fetcher in '_fetcher' on success.
*/
Status _scheduleFetcher(std::unique_ptr fetcher);
/**
* Returns optime of first oplog entry from fetcher response.
* Returns null optime on error.
*/
OpTime _parseRemoteEarliestOpTime(const HostAndPort& candidate,
const Fetcher::QueryResponse& queryResponse);
/**
* Callback for fetching first oplog entry on sync source.
*/
void _firstOplogEntryFetcherCallback(const StatusWith& queryResult,
HostAndPort candidate,
OpTime earliestOpTimeSeen);
/**
* Schedules a replSetGetRBID command against the candidate to fetch its current rollback id.
*/
void _scheduleRBIDRequest(HostAndPort candidate, OpTime earliestOpTimeSeen);
void _rbidRequestCallback(HostAndPort candidate,
OpTime earliestOpTimeSeen,
const executor::TaskExecutor::RemoteCommandCallbackArgs& rbidReply);
/**
* Checks query response for required optime.
*/
Status _compareRequiredOpTimeWithQueryResponse(const Fetcher::QueryResponse& queryResponse);
/**
* Callback for checking if the remote oplog contains '_requiredOpTime'.
*/
void _requiredOpTimeFetcherCallback(const StatusWith& queryResult,
HostAndPort candidate,
OpTime earliestOpTimeSeen);
/**
* Obtains new sync source candidate and schedules remote command to fetcher first oplog entry.
* May transition state to Complete.
* Returns status that could be used as result for startup().
*/
Status _chooseAndProbeNextSyncSource(OpTime earliestOpTimeSeen);
/**
* Invokes completion callback and transitions state to State::kComplete.
* Returns result.getStatus().
*/
Status _finishCallback(StatusWith result);
Status _finishCallback(const SyncSourceResolverResponse& response);
// Executor used to send remote commands to sync source candidates.
executor::TaskExecutor* const _taskExecutor;
// Sync source selector used to obtain sync source candidates and for us to blacklist non-viable
// candidates.
SyncSourceSelector* const _syncSourceSelector;
// A viable sync source must contain a starting oplog entry with a timestamp equal or earlier
// than the timestamp in '_lastOpTimeFetched'.
const OpTime _lastOpTimeFetched;
// If '_requiredOpTime' is not null, a viable sync source must contain an oplog entry with an
// optime equal to this value.
const OpTime _requiredOpTime;
// This is invoked exactly once after startup. The caller gets the results of the sync source
// resolver via this callback in a SyncSourceResolverResponse struct when the resolver finishes.
const OnCompletionFn _onCompletion;
// The rbid we will return to our caller.
int _rbid;
// Protects members of this sync source resolver defined below.
mutable stdx::mutex _mutex;
mutable stdx::condition_variable _condition;
// State transitions:
// PreStart --> Running --> ShuttingDown --> Complete
// It is possible to skip intermediate states. For example,
// Calling shutdown() when the resolver has not started will transition from PreStart directly
// to Complete.
enum class State { kPreStart, kRunning, kShuttingDown, kComplete };
State _state = State::kPreStart;
// Fetches first oplog entry on sync source candidate.
std::unique_ptr _fetcher;
// Holds reference to fetcher in the process of shutting down.
std::unique_ptr _shuttingDownFetcher;
executor::TaskExecutor::CallbackHandle _rbidCommandHandle;
};
} // namespace repl
} // namespace mongo