src/qpid/ha/QueueGuard.h

#ifndef QPID_HA_QUEUEGUARD_H
#define QPID_HA_QUEUEGUARD_H

/*
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 *
 */

#include "types.h"
#include "hash.h"
#include "LogPrefix.h"
#include "qpid/types/Uuid.h"
#include "qpid/sys/Mutex.h"
#include "qpid/sys/unordered_map.h"
#include <boost/shared_ptr.hpp>
#include <boost/intrusive_ptr.hpp>
#include <deque>
#include <set>

namespace qpid {
namespace broker {
class Queue;
struct QueuedMessage;
class Message;
class AsyncCompletion;
}

namespace ha {
class BrokerInfo;
class ReplicatingSubscription;

/**
 * A queue guard is a QueueObserver that delays completion of new messages
 * arriving on a queue.  It works as part of a ReplicatingSubscription to ensure
 * messages are not acknowledged till they have been replicated.
 *
 * The guard can be created before the ReplicatingSubscription to protect
 * messages arriving before the creation of the subscription.
 *
 * THREAD SAFE: Concurrent calls:
 *  - enqueued() via QueueObserver in arbitrary connection threads.
 *  - cancel(), complete() from ReplicatingSubscription in subscription thread.
 *
 */
class QueueGuard {
  public:
    QueueGuard(broker::Queue& q, const BrokerInfo&, const LogPrefix&);
    ~QueueGuard();

    /** QueueObserver override. Delay completion of the message.
     * NOTE: Called under the queues message lock.
     */
    void enqueued(const broker::Message&);

    /** QueueObserver override: Complete a delayed message.
     * NOTE: Called under the queues message lock.
     */
    void dequeued(const broker::Message&);

    /** Complete a delayed message.
     *@return true if the ID was delayed
     */
    bool complete(ReplicationId);

    /** Complete all delayed messages. */
    void cancel();

    /** Return the first known guarded position on the queue.  It is possible
     * that the guard has seen a few messages before this point.
     */
    QueuePosition getFirst() const { return first; } // Thread safe: Immutable.

  private:
    class QueueObserver;
    typedef qpid::sys::unordered_map<ReplicationId,
                                     boost::intrusive_ptr<broker::AsyncCompletion>,
                                     Hasher<ReplicationId> > Delayed;

    bool complete(ReplicationId, sys::Mutex::ScopedLock &);
    void complete(Delayed::iterator, sys::Mutex::ScopedLock &);

    sys::Mutex lock;
    QueuePosition first;
    bool cancelled;
    LogPrefix2 logPrefix;
    broker::Queue& queue;
    Delayed delayed;
    boost::shared_ptr<QueueObserver> observer;
};
}} // namespace qpid::ha

#endif  /*!QPID_HA_QUEUEGUARD_H*/