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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 <list>
#include <map>
#include <memory>
#include <vector>
#include <poll.h>
#include "mongo/platform/mutex.h"
#include "mongo/stdx/unordered_map.h"
#include "mongo/transport/asio/asio_session.h"
#include "mongo/transport/baton.h"
#include "mongo/util/functional.h"
#include "mongo/util/future.h"
#include "mongo/util/hierarchical_acquisition.h"
namespace mongo {
namespace transport {
/**
* AsioTransportLayer Baton implementation for linux.
*
* We implement our networking reactor on top of poll + eventfd for wakeups
*/
class AsioNetworkingBaton : public NetworkingBaton {
public:
AsioNetworkingBaton(OperationContext* opCtx) : _opCtx(opCtx) {}
~AsioNetworkingBaton() {
invariant(!_opCtx);
invariant(_sessions.empty());
invariant(_scheduled.empty());
invariant(_timers.empty());
}
// Overrides for `OutOfLineExecutor`
void schedule(Task func) noexcept override;
// Overrides for `Waitable` and `Notifyable`
void notify() noexcept override;
Waitable::TimeoutState run_until(ClockSource* clkSource, Date_t deadline) noexcept override;
void run(ClockSource* clkSource) noexcept override;
// Overrides for `Baton`
void markKillOnClientDisconnect() noexcept override;
// Overrides for `NetworkingBaton`
Future<void> addSession(Session& session, Type type) noexcept override;
Future<void> waitUntil(const ReactorTimer& timer, Date_t expiration) noexcept override;
Future<void> waitUntil(Date_t expiration, const CancellationToken&) noexcept override;
bool cancelSession(Session& session) noexcept override;
bool cancelTimer(const ReactorTimer& timer) noexcept override;
bool canWait() noexcept override;
private:
struct Timer {
size_t id; // Stores the unique identifier for the timer, provided by `ReactorTimer`.
Promise<void> promise;
};
struct TransportSession {
int fd;
short events; // Events to consider while polling for this session (e.g., `POLLIN`).
Promise<void> promise;
};
bool _cancelTimer(size_t timerId) noexcept;
/*
* Internally, `AsioNetworkingBaton` thinks in terms of synchronized units of work. This is
* because a baton effectively represents a green thread with the potential to add or remove
* work (i.e., jobs) at any time. Thus, scheduled jobs must release their lock before executing
* any task external to the baton (e.g., `OutOfLineExecutor::Task`, `TransportSession:promise`,
* and `ReactorTimer::promise`).
*/
using Job = unique_function<void(stdx::unique_lock<Mutex>)>;
/**
* Invokes a job with exclusive access to the baton's internals.
*
* If the baton is currently polling (i.e., `_inPoll` is `true`), the polling thread owns the
* baton, so we schedule the job and notify the polling thread to wake up and run the job.
*
* Otherwise, take exclusive access and run the job on the current thread.
*
* Note that `_safeExecute()` will throw if the baton has been detached.
*
* Also note that the job may not run inline, and may get scheduled to run by the baton, so it
* should never throw.
*/
void _safeExecute(stdx::unique_lock<Mutex> lk, Job job);
/**
* Blocks polling on the registered sessions until one of the following happens:
* - `notify()` is called, either directly or through other methods (e.g., `schedule()`).
* - One of the timers scheduled on this baton times out.
* - There is an event for at least one of the registered sessions (e.g., data is available).
* Returns the list of promises that must be fulfilled as the result of polling.
*/
std::list<Promise<void>> _poll(stdx::unique_lock<Mutex>&, ClockSource*);
Future<void> _addSession(Session& session, short events);
void detachImpl() noexcept override;
Mutex _mutex = MONGO_MAKE_LATCH(HierarchicalAcquisitionLevel(0), "AsioNetworkingBaton::_mutex");
OperationContext* _opCtx;
bool _inPoll = false;
// Stores the sessions we need to poll on.
stdx::unordered_map<SessionId, TransportSession> _sessions;
/**
* We use two structures to maintain timers:
* - `_timers` keeps a sorted list of timers according to their expiration date.
* - `_timersById` allows using the unique timer id to find and cancel a timer in constant time.
*/
std::multimap<Date_t, Timer> _timers;
stdx::unordered_map<size_t, std::multimap<Date_t, Timer>::iterator> _timersById;
// Tasks scheduled for deferred execution.
std::vector<Job> _scheduled;
/*
* We hold the following values at the object level to save on allocations when a baton is
* waited on many times over the course of its lifetime:
* `_pollSet`: the poll set for `::poll`.
* `_pollSessions`: maps members of `_pollSet` to their corresponding session in `_sessions`.
*/
std::vector<::pollfd> _pollSet;
std::vector<decltype(_sessions)::iterator> _pollSessions;
};
} // namespace transport
} // namespace mongo
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