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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 <deque>
#include "mongo/base/status.h"
#include "mongo/platform/atomic_word.h"
#include "mongo/stdx/condition_variable.h"
#include "mongo/stdx/mutex.h"
#include "mongo/transport/service_executor.h"
#include "mongo/transport/service_executor_task_names.h"
namespace mongo {
namespace transport {
/**
* The reserved service executor emulates a thread per connection.
* Each connection has its own worker thread where jobs get scheduled.
*
* The executor will start reservedThreads on start, and create a new thread every time it
* starts a new thread, ensuring there are always reservedThreads available for work - this
* means that even when you hit the NPROC ulimit, there will still be threads ready to
* accept work. When threads exit, they will go back to waiting for work if there are fewer
* than reservedThreads available.
*/
class ServiceExecutorReserved final : public ServiceExecutor {
public:
explicit ServiceExecutorReserved(ServiceContext* ctx, std::string name, size_t reservedThreads);
Status start() override;
Status shutdown(Milliseconds timeout) override;
Status schedule(Task task, ScheduleFlags flags, ServiceExecutorTaskName taskName) override;
Mode transportMode() const override {
return Mode::kSynchronous;
}
void appendStats(BSONObjBuilder* bob) const override;
private:
Status _startWorker();
static thread_local std::deque<Task> _localWorkQueue;
static thread_local int _localRecursionDepth;
static thread_local int64_t _localThreadIdleCounter;
AtomicWord<bool> _stillRunning{false};
mutable stdx::mutex _mutex;
stdx::condition_variable _threadWakeup;
stdx::condition_variable _shutdownCondition;
std::deque<Task> _readyTasks;
AtomicWord<unsigned> _numRunningWorkerThreads{0};
size_t _numReadyThreads{0};
size_t _numStartingThreads{0};
const std::string _name;
const size_t _reservedThreads;
};
} // namespace transport
} // namespace mongo
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