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/**
* Copyright (C) 2016 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* 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 GNU Affero General 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 "mongo/base/status.h"
#include "mongo/stdx/functional.h"
#include "mongo/transport/session.h"
#include "mongo/transport/ticket.h"
#include "mongo/util/net/message.h"
#include "mongo/util/time_support.h"
namespace mongo {
namespace transport {
class TicketImpl;
/**
* The TransportLayer moves Messages between transport::Endpoints and the database.
* This class owns an Acceptor that generates new endpoints from which it can
* source Messages.
*
* The TransportLayer creates Session objects and maps them internally to
* endpoints. New Sessions are passed to the database (via a ServiceEntryPoint)
* to be run. The database must then call additional methods on the TransportLayer
* to manage the Session in a get-Message, handle-Message, return-Message cycle.
* It must do this on its own thread(s).
*
* References to the TransportLayer should be stored on service context objects.
*/
class TransportLayer {
MONGO_DISALLOW_COPYING(TransportLayer);
public:
static const Status SessionUnknownStatus;
static const Status ShutdownStatus;
static const Status TicketSessionUnknownStatus;
static const Status TicketSessionClosedStatus;
friend class Session;
virtual ~TransportLayer() = default;
/**
* Source (receive) a new Message for this Session.
*
* This method returns a work Ticket. The caller must complete the Ticket by
* passing it to either TransportLayer::wait() or TransportLayer::asyncWait().
*
* If an expiration date is given, the returned Ticket will expire at that time.
*
* When run, the returned Ticket will be exchanged for a Status. If the
* TransportLayer is unable to source a Message, this will be a failed status,
* and the passed-in Message buffer may be left in an invalid state.
*/
virtual Ticket sourceMessage(const SessionHandle& session,
Message* message,
Date_t expiration = Ticket::kNoExpirationDate) = 0;
/**
* Sink (send) a new Message for this Session. This method should be used
* to send replies to a given host.
*
* This method returns a work Ticket. The caller must complete the Ticket by
* passing it to either TransportLayer::wait() or TransportLayer::asyncWait().
*
* If an expiration date is given, the returned Ticket will expire at that time.
*
* When run, the returned Ticket will be exchanged for a Status. If the
* TransportLayer is unable to sink the Message, this will be a failed status.
*
* This method does NOT take ownership of the sunk Message, which must be cleaned
* up by the caller.
*/
virtual Ticket sinkMessage(const SessionHandle& session,
const Message& message,
Date_t expiration = Ticket::kNoExpirationDate) = 0;
/**
* Perform a synchronous wait on the given work Ticket. When this call returns,
* the Ticket will have been completed. A call to wait() consumes the Ticket.
*
* This thread may be used by the TransportLayer to run other Tickets that were
* enqueued prior to this call.
*/
virtual Status wait(Ticket&& ticket) = 0;
/**
* Callback for Tickets that are run via asyncWait().
*/
using TicketCallback = stdx::function<void(Status)>;
/**
* Perform an asynchronous wait on the given work Ticket. Once the Ticket has been
* completed, the passed-in callback will be invoked.
*
* This thread will not be used by the TransportLayer to perform work. The callback
* passed to asyncWait() may be run on any thread.
*/
virtual void asyncWait(Ticket&& ticket, TicketCallback callback) = 0;
/**
* End the given Session. Tickets for this Session that have already been
* started via wait() or asyncWait() will complete, but may return a failed Status.
* Future calls to wait() or asyncWait() for this Session will fail. If this
* TransportLayer implementation is networked, any connections for this Session will
* be closed.
*
* ~Session() will automatically call end() with itself.
*
* This method is idempotent and synchronous.
*/
virtual void end(const SessionHandle& session) = 0;
/**
* Start the TransportLayer. After this point, the TransportLayer will begin accepting active
* sessions from new transport::Endpoints.
*/
virtual Status start() = 0;
/**
* Shut the TransportLayer down. After this point, the TransportLayer will
* end all active sessions and won't accept new transport::Endpoints. Any
* future calls to wait() or asyncWait() will fail. This method is synchronous and
* will not return until all sessions have ended and any network connections have been
* closed.
*/
virtual void shutdown() = 0;
/**
* Optional method for subclasses to setup their state before being ready to accept
* connections.
*/
virtual Status setup() = 0;
protected:
TransportLayer() = default;
/**
* Return the implementation of this Ticket.
*/
TicketImpl* getTicketImpl(const Ticket& ticket) {
return ticket.impl();
}
std::unique_ptr<TicketImpl> getOwnedTicketImpl(Ticket&& ticket) {
return std::move(ticket).releaseImpl();
}
/**
* Return the transport layer of this Ticket.
*/
TransportLayer* getTicketTransportLayer(const Ticket& ticket) {
return ticket._tl;
}
};
} // namespace transport
} // namespace mongo
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