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/**
* Copyright (C) 2020-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 <boost/optional.hpp>
#include <memory>
#include "mongo/base/status.h"
#include "mongo/db/service_context.h"
#include "mongo/platform/atomic_word.h"
#include "mongo/platform/mutex.h"
#include "mongo/stdx/condition_variable.h"
#include "mongo/stdx/thread.h"
#include "mongo/stdx/unordered_map.h"
#include "mongo/transport/service_executor.h"
#include "mongo/util/concurrency/thread_pool.h"
#include "mongo/util/concurrency/with_lock.h"
#include "mongo/util/future.h"
#include "mongo/util/hierarchical_acquisition.h"
namespace mongo {
namespace transport {
/**
* A service executor that uses a fixed (configurable) number of threads to execute tasks.
* This executor always yields before executing scheduled tasks, and never yields before scheduling
* new tasks.
*/
class ServiceExecutorFixed final : public ServiceExecutor,
public std::enable_shared_from_this<ServiceExecutorFixed> {
static constexpr auto kDiagnosticLogLevel = 3;
public:
explicit ServiceExecutorFixed(ServiceContext* ctx, ThreadPool::Limits limits);
explicit ServiceExecutorFixed(ThreadPool::Limits limits)
: ServiceExecutorFixed(nullptr, std::move(limits)) {}
virtual ~ServiceExecutorFixed();
static ServiceExecutorFixed* get(ServiceContext* ctx);
Status start() override;
Status shutdown(Milliseconds timeout) override;
size_t getRunningThreads() const override;
void appendStats(BSONObjBuilder* bob) const override;
/**
* Returns the recursion depth of the active executor thread.
* It is forbidden to invoke this method outside scheduled tasks.
*/
int getRecursionDepthForExecutorThread() const;
std::unique_ptr<TaskRunner> makeTaskRunner() override;
private:
enum class State { kNotStarted, kRunning, kStopping, kStopped };
// Maintains the execution state (e.g., recursion depth) for executor threads
class ExecutorThreadContext;
struct Stats;
struct Waiter {
std::shared_ptr<Session> session;
Task onCompletionCallback;
};
void _schedule(Task task);
void _runOnDataAvailable(const std::shared_ptr<Session>& session, Task onCompletionCallback);
const std::string& _name() const;
/** Requires `_mutex` locked. */
void _checkForShutdown();
/** Requires `_mutex` locked. */
void _beginShutdown();
void _finalize() noexcept;
/** Requires `_mutex` locked by `lk`. */
bool _waitForStop(stdx::unique_lock<Mutex>& lk, boost::optional<Milliseconds> timeout);
/** `_state` transitions: kNotStarted -> kRunning -> kStopping -> kStopped */
State _state = State::kNotStarted;
std::unique_ptr<Stats> _stats;
ServiceContext* const _svcCtx;
mutable Mutex _mutex =
MONGO_MAKE_LATCH(HierarchicalAcquisitionLevel(0), "ServiceExecutorFixed::_mutex");
stdx::condition_variable _shutdownCondition;
SharedPromise<void> _shutdownComplete;
ThreadPool::Options _options;
std::shared_ptr<ThreadPool> _threadPool;
std::list<Waiter> _waiters;
static thread_local std::unique_ptr<ExecutorThreadContext> _executorContext;
};
} // namespace transport
} // namespace mongo
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