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/**
* Copyright (C) 2019-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 <memory>
#include "mongo/db/baton.h"
#include "mongo/util/cancellation.h"
#include "mongo/util/functional.h"
#include "mongo/util/future.h"
#include "mongo/util/out_of_line_executor.h"
#include "mongo/util/time_support.h"
#include "mongo/util/waitable.h"
namespace mongo {
class OperationContext;
namespace transport {
class TransportLayer;
class Session;
class ReactorTimer;
/**
* A NetworkingBaton is basically a networking reactor, with limited functionality and parallel
* forward progress guarantees. Rather than asynchronously running tasks through one, the baton
* records the intent of those tasks and defers waiting and execution to a later call to run();
*
* NetworkingBaton's provide a mechanism to allow consumers of a transport layer to execute IO
* themselves, rather than having this occur on another thread. This can improve performance by
* minimizing context switches, as well as improving the readability of stack traces by grounding
* async execution on top of a regular client call stack.
*/
class NetworkingBaton : public Baton {
public:
/**
* Adds a session, returning a future which activates on read/write-ability of the session.
*/
enum class Type {
In,
Out,
};
virtual Future<void> addSession(Session& session, Type type) noexcept = 0;
/**
* Adds a timer, returning a future which activates after a deadline.
*/
virtual Future<void> waitUntil(const ReactorTimer& timer, Date_t expiration) noexcept = 0;
virtual Future<void> waitUntil(Date_t expiration, const CancellationToken& token) noexcept = 0;
/**
* Cancels waiting on a session.
*
* Returns true if the session was in the baton to be cancelled.
*/
virtual bool cancelSession(Session& session) noexcept = 0;
/**
* Cancels waiting on a timer
*
* Returns true if the timer was in the baton to be cancelled.
*/
virtual bool cancelTimer(const ReactorTimer& timer) noexcept = 0;
NetworkingBaton* networking() noexcept final {
return this;
}
virtual bool canWait() noexcept = 0;
};
} // namespace transport
} // namespace mongo
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