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/**
* Copyright 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 <vector>
#include "mongo/base/disallow_copying.h"
#include "mongo/db/repl/replication_executor.h"
#include "mongo/stdx/functional.h"
namespace mongo {
template <typename T> class StatusWith;
namespace repl {
class ScatterGatherAlgorithm;
/**
* Implementation of a scatter-gather behavior using a ReplicationExecutor.
*/
class ScatterGatherRunner {
MONGO_DISALLOW_COPYING(ScatterGatherRunner);
public:
/**
* Constructs a new runner whose underlying algorithm is "algorithm".
*
* "algorithm" must remain in scope until the runner's destructor completes.
*/
explicit ScatterGatherRunner(ScatterGatherAlgorithm* algorithm);
~ScatterGatherRunner();
/**
* Runs the scatter-gather process using "executor", and blocks until it completes.
*
* Must _not_ be run from inside the executor context.
*
* Returns ErrorCodes::ShutdownInProgress if the executor enters or is already in
* the shutdown state before run() can schedule execution of the scatter-gather
* in the executor. Note that if the executor is shut down after the algorithm
* is scheduled but before it completes, this method will return Status::OK(),
* just as it does when it runs successfully to completion.
*/
Status run(ReplicationExecutor* executor);
/**
* Starts executing the scatter-gather process using "executor".
*
* On success, returns an event handle that will be signaled when the runner has
* finished executing the scatter-gather process. After that event has been
* signaled, it is safe for the caller to examine any state on "algorithm".
*
* This method must be called inside the executor context.
*
* onCompletion is an optional callback that will be executed in executor context
* immediately prior to signaling the event handle returned here. It must never
* throw exceptions. It may examine the state of the algorithm object.
*
* NOTE: If the executor starts to shut down before onCompletion executes, onCompletion may
* never execute, even though the returned event will eventually be signaled.
*/
StatusWith<ReplicationExecutor::EventHandle> start(
ReplicationExecutor* executor,
const stdx::function<void ()>& onCompletion = stdx::function<void ()>());
/**
* Informs the runner to cancel further processing. The "executor" argument
* must point to the same executor passed to "start()".
*
* Like start, this method must be called from within the executor context.
*/
void cancel(ReplicationExecutor* executor);
private:
/**
* Callback invoked once for every response from the network.
*/
static void _processResponse(const ReplicationExecutor::RemoteCommandCallbackArgs& cbData,
ScatterGatherRunner* runner);
/**
* Method that performs all actions required when _algorithm indicates a sufficient
* number of respones have been received.
*/
void _signalSufficientResponsesReceived(ReplicationExecutor* executor);
ScatterGatherAlgorithm* _algorithm;
stdx::function<void ()> _onCompletion;
ReplicationExecutor::EventHandle _sufficientResponsesReceived;
std::vector<ReplicationExecutor::CallbackHandle> _callbacks;
size_t _actualResponses;
bool _started;
};
} // namespace repl
} // namespace mongo
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