src/qpid/ha/QueueGuard.cpp

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 * 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
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 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
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#include "QueueGuard.h"
#include "BrokerInfo.h"
#include "qpid/broker/Queue.h"
#include "qpid/broker/QueuedMessage.h"
#include "qpid/broker/QueueObserver.h"
#include "qpid/log/Statement.h"
#include <boost/bind.hpp>
#include <sstream>

namespace qpid {
namespace ha {

using namespace broker;
using sys::Mutex;

class QueueGuard::QueueObserver : public broker::QueueObserver
{
  public:
    QueueObserver(QueueGuard& g) : guard(g) {}
    void enqueued(const broker::Message& m) { guard.enqueued(m); }
    void dequeued(const broker::Message& m) { guard.dequeued(m); }
    void acquired(const broker::Message&) {}
    void requeued(const broker::Message&) {}
  private:
    QueueGuard& guard;
};



QueueGuard::QueueGuard(broker::Queue& q, const BrokerInfo& info, const LogPrefix& lp)
    : cancelled(false), logPrefix(lp), queue(q)
{
    std::ostringstream os;
    os << "Guard of " << queue.getName() << " at ";
    info.printId(os) << ": ";
    logPrefix = os.str();
    observer.reset(new QueueObserver(*this));
    queue.getObservers().add(observer);
    // Set first after adding the observer so we know that the back of the
    // queue+1 is (or will be) a guarded position.
    QueuePosition front, back;
    q.getRange(front, back, broker::REPLICATOR);
    first = back + 1;
    QPID_LOG(debug, logPrefix << "Guarded: front " << front
             << ", back " << back
             << ", guarded " << first);
}

QueueGuard::~QueueGuard() { cancel(); }

// NOTE: Called with message lock held.
void QueueGuard::enqueued(const Message& m) {
    // Delay completion
    ReplicationId id = m.getReplicationId();
    Mutex::ScopedLock l(lock);
    if (cancelled) return;  // Don't record enqueues after we are cancelled.
    QPID_LOG(trace, logPrefix << "Delayed completion of " << logMessageId(queue, m));
    delayed[id] = m.getIngressCompletion();
    m.getIngressCompletion()->startCompleter();
}

// NOTE: Called with message lock held.
void QueueGuard::dequeued(const Message& m) {
    ReplicationId id = m.getReplicationId();
    QPID_LOG(trace, logPrefix << "Dequeued "  << logMessageId(queue, m));
    Mutex::ScopedLock l(lock);
    complete(id, l);
}

void QueueGuard::cancel() {
    queue.getObservers().remove(observer);
    Mutex::ScopedLock l(lock);
    if (cancelled) return;
    QPID_LOG(debug, logPrefix << "Cancelled");
    cancelled = true;
    while (!delayed.empty()) complete(delayed.begin(), l);
}

bool QueueGuard::complete(ReplicationId id) {
    Mutex::ScopedLock l(lock);
    return complete(id, l);
}

bool QueueGuard::complete(ReplicationId id, Mutex::ScopedLock& l) {
    // The same message can be completed twice, by
    // ReplicatingSubscription::acknowledged and dequeued. Remove it
    // from the map so we only call finishCompleter() once
    Delayed::iterator i = delayed.find(id);
    if (i != delayed.end()) {
        complete(i, l);
        return true;
    }
    return false;
}

void QueueGuard::complete(Delayed::iterator i, Mutex::ScopedLock&) {
    QPID_LOG(trace, logPrefix << "Completed " << queue.getName() << " =" << i->first);
    i->second->finishCompleter();
    delayed.erase(i);
}


}} // namespaces qpid::ha