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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
#include <functional>
#include <vector>
#include "mongo/executor/task_executor.h"
#include "mongo/platform/mutex.h"
namespace mongo {
template <typename T>
class StatusWith;
namespace repl {
class ScatterGatherAlgorithm;
/**
* Interface of a scatter-gather behavior.
*/
class ScatterGatherRunner {
ScatterGatherRunner(const ScatterGatherRunner&) = delete;
ScatterGatherRunner& operator=(const ScatterGatherRunner&) = delete;
public:
/**
* Constructs a new runner whose underlying algorithm is "algorithm".
*
* "executor" must remain in scope until the runner's destructor completes.
* "algorithm" is shared between the runner and the caller.
* "logMessage" is the process for which this ScatterGatherRunner is used. It will be included
* in log lines written by the ScatterGatherRunner for remote command requests.
*/
explicit ScatterGatherRunner(std::shared_ptr<ScatterGatherAlgorithm> algorithm,
executor::TaskExecutor* executor,
std::string logMessage);
/**
* Runs the scatter-gather process 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();
/**
* 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".
*
* The returned event will eventually be signaled.
*/
StatusWith<executor::TaskExecutor::EventHandle> start();
/**
* Informs the runner to cancel further processing.
*/
void cancel();
private:
/**
* Implementation of a scatter-gather behavior using a TaskExecutor.
*/
class RunnerImpl {
public:
explicit RunnerImpl(std::shared_ptr<ScatterGatherAlgorithm> algorithm,
executor::TaskExecutor* executor,
std::string logMessage);
/**
* 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".
*
* The returned event will eventually be signaled.
*/
StatusWith<executor::TaskExecutor::EventHandle> start(
executor::TaskExecutor::RemoteCommandCallbackFn cb);
/**
* Informs the runner to cancel further processing.
*/
void cancel();
/**
* Callback invoked once for every response from the network.
*/
void processResponse(const executor::TaskExecutor::RemoteCommandCallbackArgs& cbData);
private:
/**
* Method that performs all actions required when _algorithm indicates a sufficient
* number of responses have been received.
*/
void _signalSufficientResponsesReceived();
executor::TaskExecutor* _executor; // Not owned here.
std::shared_ptr<ScatterGatherAlgorithm> _algorithm;
std::string _logMessage;
executor::TaskExecutor::EventHandle _sufficientResponsesReceived;
std::vector<executor::TaskExecutor::CallbackHandle> _callbacks;
bool _started = false;
Mutex _mutex = MONGO_MAKE_LATCH("RunnerImpl::_mutex");
};
executor::TaskExecutor* _executor; // Not owned here.
// This pointer of RunnerImpl will be shared with remote command callbacks to make sure
// callbacks can access the members safely.
std::shared_ptr<RunnerImpl> _impl;
};
} // namespace repl
} // namespace mongo
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