Package org.apache.activemq.broker.region

Source Code of org.apache.activemq.broker.region.Queue

/**
* 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.
*/
package org.apache.activemq.broker.region;

import org.apache.activemq.broker.BrokerService;
import org.apache.activemq.broker.ConnectionContext;
import org.apache.activemq.broker.ProducerBrokerExchange;
import org.apache.activemq.broker.region.cursors.PendingMessageCursor;
import org.apache.activemq.broker.region.cursors.StoreQueueCursor;
import org.apache.activemq.broker.region.cursors.VMPendingMessageCursor;
import org.apache.activemq.broker.region.group.MessageGroupHashBucketFactory;
import org.apache.activemq.broker.region.group.MessageGroupMap;
import org.apache.activemq.broker.region.group.MessageGroupMapFactory;
import org.apache.activemq.broker.region.policy.DispatchPolicy;
import org.apache.activemq.broker.region.policy.RoundRobinDispatchPolicy;
import org.apache.activemq.command.ActiveMQDestination;
import org.apache.activemq.command.ConsumerId;
import org.apache.activemq.command.ExceptionResponse;
import org.apache.activemq.command.Message;
import org.apache.activemq.command.MessageAck;
import org.apache.activemq.command.MessageDispatchNotification;
import org.apache.activemq.command.MessageId;
import org.apache.activemq.command.ProducerAck;
import org.apache.activemq.command.ProducerInfo;
import org.apache.activemq.command.Response;
import org.apache.activemq.filter.BooleanExpression;
import org.apache.activemq.filter.MessageEvaluationContext;
import org.apache.activemq.filter.NonCachedMessageEvaluationContext;
import org.apache.activemq.selector.SelectorParser;
import org.apache.activemq.store.MessageRecoveryListener;
import org.apache.activemq.store.MessageStore;
import org.apache.activemq.thread.DeterministicTaskRunner;
import org.apache.activemq.thread.Scheduler;
import org.apache.activemq.thread.Task;
import org.apache.activemq.thread.TaskRunner;
import org.apache.activemq.thread.TaskRunnerFactory;
import org.apache.activemq.transaction.Synchronization;
import org.apache.activemq.usage.Usage;
import org.apache.activemq.usage.UsageListener;
import org.apache.activemq.util.BrokerSupport;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import java.io.IOException;
import java.util.AbstractList;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Set;
import java.util.concurrent.CopyOnWriteArraySet;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import javax.jms.InvalidSelectorException;
import javax.jms.JMSException;


/**
* The Queue is a List of MessageEntry objects that are dispatched to matching
* subscriptions.
*
* @version $Revision: 1.28 $
*/
public class Queue extends BaseDestination implements Task, UsageListener {
    protected static final Log LOG = LogFactory.getLog(Queue.class);
    protected TaskRunnerFactory taskFactory;
    protected TaskRunner taskRunner;   
    protected final List<Subscription> consumers = new ArrayList<Subscription>(50);
    protected PendingMessageCursor messages;
    private final LinkedHashMap<MessageId,QueueMessageReference> pagedInMessages = new LinkedHashMap<MessageId,QueueMessageReference>();
    // Messages that are paged in but have not yet been targeted at a subscription
    private List<QueueMessageReference> pagedInPendingDispatch = new ArrayList<QueueMessageReference>(100);
    private MessageGroupMap messageGroupOwners;
    private DispatchPolicy dispatchPolicy = new RoundRobinDispatchPolicy();
    private MessageGroupMapFactory messageGroupMapFactory = new MessageGroupHashBucketFactory();
    private final Object sendLock = new Object();
    private ExecutorService executor;
    protected final LinkedList<Runnable> messagesWaitingForSpace = new LinkedList<Runnable>();
    private final Object dispatchMutex = new Object();
    private boolean useConsumerPriority=true;
    private boolean strictOrderDispatch=false;
    private QueueDispatchSelector dispatchSelector;
    private boolean optimizedDispatch=false;
    private boolean firstConsumer = false;
    private int timeBeforeDispatchStarts = 0;
    private int consumersBeforeDispatchStarts = 0;
    private CountDownLatch consumersBeforeStartsLatch;
    private final Runnable sendMessagesWaitingForSpaceTask = new Runnable() {
        public void run() {
            wakeup();
        }
    };
    private final Runnable expireMessagesTask = new Runnable() {
        public void run() {
            expireMessages();         
        }
    };
    private final Object iteratingMutex = new Object() {};
    private static final Scheduler scheduler = Scheduler.getInstance();
   
    private static final Comparator<Subscription>orderedCompare = new Comparator<Subscription>() {

        public int compare(Subscription s1, Subscription s2) {
            //We want the list sorted in descending order
            return s2.getConsumerInfo().getPriority() - s1.getConsumerInfo().getPriority();
        }       
    };
              
    public Queue(BrokerService brokerService, final ActiveMQDestination destination, MessageStore store,DestinationStatistics parentStats,
                 TaskRunnerFactory taskFactory) throws Exception {
        super(brokerService, store, destination, parentStats);
        this.taskFactory=taskFactory;      
        this.dispatchSelector=new QueueDispatchSelector(destination);
    }

    public List<Subscription> getConsumers() {
        synchronized (consumers) {
            return new ArrayList<Subscription>(consumers);
        }
    }

    // make the queue easily visible in the debugger from its task runner threads
    final class QueueThread extends Thread {
        final Queue queue;
        public QueueThread(Runnable runnable, String name,
                Queue queue) {
            super(runnable, name);
            this.queue = queue;
        }
    }
   
    public void initialize() throws Exception {
        if (this.messages == null) {
            if (destination.isTemporary() || broker == null || store == null) {
                this.messages = new VMPendingMessageCursor();
            } else {
                this.messages = new StoreQueueCursor(broker, this);
            }
        }
        // If a VMPendingMessageCursor don't use the default Producer System Usage
        // since it turns into a shared blocking queue which can lead to a network deadlock. 
        // If we are cursoring to disk..it's not and issue because it does not block due
        // to large disk sizes.
        if( messages instanceof VMPendingMessageCursor ) {
            this.systemUsage = brokerService.getSystemUsage();
            memoryUsage.setParent(systemUsage.getMemoryUsage());
        }
       
        if (isOptimizedDispatch()) {
            this.taskRunner = taskFactory.createTaskRunner(this, "TempQueue:  " + destination.getPhysicalName());
        }else {
            final Queue queue = this;
            this.executor =  Executors.newSingleThreadExecutor(new ThreadFactory() {
                public Thread newThread(Runnable runnable) {
                    Thread thread = new QueueThread(runnable, "QueueThread:"+destination, queue);
                    thread.setDaemon(true);
                    thread.setPriority(Thread.NORM_PRIORITY);
                    return thread;
                }
            });
              
            this.taskRunner = new DeterministicTaskRunner(this.executor,this);
        }
       
        super.initialize();
        if (store != null) {
            // Restore the persistent messages.
            messages.setSystemUsage(systemUsage);
            messages.setEnableAudit(isEnableAudit());
            messages.setMaxAuditDepth(getMaxAuditDepth());
            messages.setMaxProducersToAudit(getMaxProducersToAudit());
            messages.setUseCache(isUseCache());
            messages.setMemoryUsageHighWaterMark(getCursorMemoryHighWaterMark());
            if (messages.isRecoveryRequired()) {
                store.recover(new MessageRecoveryListener() {

                    public boolean recoverMessage(Message message) {
                        // Message could have expired while it was being
                        // loaded..
                        if (broker.isExpired(message)) {
                            messageExpired(createConnectionContext(), createMessageReference(message));
                            // drop message will decrement so counter balance here
                            destinationStatistics.getMessages().increment();
                            return true;
                        }
                        if (hasSpace()) {
                            message.setRegionDestination(Queue.this);
                            synchronized (messages) {
                                try {
                                    messages.addMessageLast(message);
                                } catch (Exception e) {
                                    LOG.fatal("Failed to add message to cursor", e);
                                }
                            }
                            destinationStatistics.getMessages().increment();
                            return true;
                        }
                        return false;
                    }

                    public boolean recoverMessageReference(MessageId messageReference) throws Exception {
                        throw new RuntimeException("Should not be called.");
                    }

                    public boolean hasSpace() {
                        return true;
                    }
                   
                    public boolean isDuplicate(MessageId id) {
                        return false;
                    }
                });
            }else {
                int messageCount = store.getMessageCount();
                destinationStatistics.getMessages().setCount(messageCount);
            }
        }
    }

    /*
     * Holder for subscription and pagedInMessages as a browser
     * needs access to existing messages in the queue that have
     * already been dispatched
     */
    class BrowserDispatch {
        ArrayList<QueueMessageReference> messages;
        QueueBrowserSubscription browser;
       
        public BrowserDispatch(QueueBrowserSubscription browserSubscription,
                Collection<QueueMessageReference> values) {
           
            messages =  new ArrayList<QueueMessageReference>(values);
            browser = browserSubscription;
            browser.incrementQueueRef();
        }
       
        void done() {
            try {
                browser.decrementQueueRef();
            } catch (Exception e) {
                LOG.warn("decrement ref on browser: " + browser, e);
            }
        }

        public QueueBrowserSubscription getBrowser() {
            return browser;
        }
    }
  
    LinkedList<BrowserDispatch> browserDispatches = new LinkedList<BrowserDispatch>();

    public void addSubscription(ConnectionContext context, Subscription sub) throws Exception {
        // synchronize with dispatch method so that no new messages are sent
        // while setting up a subscription. avoid out of order messages,
        // duplicates, etc.
        synchronized(dispatchMutex) {
       
            sub.add(context, this);
            destinationStatistics.getConsumers().increment();

            // needs to be synchronized - so no contention with dispatching
            synchronized (consumers) {
             
              // set a flag if this is a first consumer
              if (consumers.size() == 0) {
                firstConsumer = true;
                if (consumersBeforeDispatchStarts != 0) {
                  consumersBeforeStartsLatch = new CountDownLatch(consumersBeforeDispatchStarts - 1);
                }
              } else {
                  if (consumersBeforeStartsLatch != null) {
                    consumersBeforeStartsLatch.countDown();
                  }
              }
             
                addToConsumerList(sub);
                if (sub.getConsumerInfo().isExclusive()) {
                    Subscription exclusiveConsumer = dispatchSelector.getExclusiveConsumer();
                    if(exclusiveConsumer==null) {
                        exclusiveConsumer=sub;
                    }else if (sub.getConsumerInfo().getPriority() > exclusiveConsumer.getConsumerInfo().getPriority()){
                        exclusiveConsumer=sub;
                    }
                    dispatchSelector.setExclusiveConsumer(exclusiveConsumer);
                }
            }
           
            if (sub instanceof QueueBrowserSubscription ) {
                QueueBrowserSubscription browserSubscription = (QueueBrowserSubscription) sub;
             
                // do again in iterate to ensure new messages are dispatched
                pageInMessages(false);
               
              synchronized (pagedInMessages) {
                  if (!pagedInMessages.isEmpty()) {
                      BrowserDispatch browserDispatch = new BrowserDispatch(browserSubscription, pagedInMessages.values());
                      browserDispatches.addLast(browserDispatch);
                  }
              }
            }
            if (!(this.optimizedDispatch || isSlave())) {
                wakeup();
            }
        }
        if (this.optimizedDispatch || isSlave()) {
            // Outside of dispatchLock() to maintain the lock hierarchy of
            // iteratingMutex -> dispatchLock. - see https://issues.apache.org/activemq/browse/AMQ-1878
            wakeup();
        }
    }

    public void removeSubscription(ConnectionContext context, Subscription sub, long lastDeiveredSequenceId)
            throws Exception {
        destinationStatistics.getConsumers().decrement();
        // synchronize with dispatch method so that no new messages are sent
        // while removing up a subscription.
        synchronized(dispatchMutex) {
            if (LOG.isDebugEnabled()) {
                LOG.debug("remove sub: " + sub + ", lastDeliveredSeqId: " + lastDeiveredSequenceId
                        + ", dequeues: " + getDestinationStatistics().getDequeues().getCount()
                        + ", dispatched: " + getDestinationStatistics().getDispatched().getCount()
                        + ", inflight: " + getDestinationStatistics().getInflight().getCount());
            }
            synchronized (consumers) {
                removeFromConsumerList(sub);
                if (sub.getConsumerInfo().isExclusive()) {
                    Subscription exclusiveConsumer = dispatchSelector
                            .getExclusiveConsumer();
                    if (exclusiveConsumer == sub) {
                        exclusiveConsumer = null;
                        for (Subscription s : consumers) {
                            if (s.getConsumerInfo().isExclusive()
                                    && (exclusiveConsumer == null
                                    || s.getConsumerInfo().getPriority() > exclusiveConsumer
                                            .getConsumerInfo().getPriority())) {
                                exclusiveConsumer = s;

                            }
                        }
                        dispatchSelector.setExclusiveConsumer(exclusiveConsumer);
                    }
                }
                ConsumerId consumerId = sub.getConsumerInfo().getConsumerId();
                getMessageGroupOwners().removeConsumer(consumerId);
               
                // redeliver inflight messages
                List<QueueMessageReference> list = new ArrayList<QueueMessageReference>();
                for (MessageReference ref : sub.remove(context, this)) {
                    QueueMessageReference qmr = (QueueMessageReference)ref;
                    if( qmr.getLockOwner()==sub ) {
                        qmr.unlock();
                        // only increment redelivery if it was delivered or we have no delivery information
                        if (lastDeiveredSequenceId == 0 || qmr.getMessageId().getBrokerSequenceId() <= lastDeiveredSequenceId) {
                            qmr.incrementRedeliveryCounter();
                        }
                    }
                    list.add(qmr);
                }
               
                if (!list.isEmpty()) {
                    doDispatch(list);
                }
            }
            if (!(this.optimizedDispatch || isSlave())) {
                wakeup();
            }
        }
        if (this.optimizedDispatch || isSlave()) {
            // Outside of dispatchLock() to maintain the lock hierarchy of
            // iteratingMutex -> dispatchLock. - see https://issues.apache.org/activemq/browse/AMQ-1878
            wakeup();
        }
    }

    public void send(final ProducerBrokerExchange producerExchange, final Message message) throws Exception {
        final ConnectionContext context = producerExchange.getConnectionContext();
        // There is delay between the client sending it and it arriving at the
        // destination.. it may have expired.
        message.setRegionDestination(this);
        final ProducerInfo producerInfo = producerExchange.getProducerState().getInfo();
        final boolean sendProducerAck = !message.isResponseRequired() && producerInfo.getWindowSize() > 0 && !context.isInRecoveryMode();
        if (message.isExpired()) {
            //message not stored - or added to stats yet - so chuck here
            broker.getRoot().messageExpired(context, message);
            if (sendProducerAck) {
                ProducerAck ack = new ProducerAck(producerInfo.getProducerId(), message.getSize());
                context.getConnection().dispatchAsync(ack);
            }
            return;
        }
        if(memoryUsage.isFull()) {
            isFull(context, memoryUsage);
            fastProducer(context, producerInfo);
            if (isProducerFlowControl() && context.isProducerFlowControl()) {
                if(warnOnProducerFlowControl) {
                    warnOnProducerFlowControl = false;
                    LOG.info("Usage Manager memory limit reached on " +getActiveMQDestination().getQualifiedName() + ". Producers will be throttled to the rate at which messages are removed from this destination to prevent flooding it." +
                            " See http://activemq.apache.org/producer-flow-control.html for more info");
                }
               
                if (systemUsage.isSendFailIfNoSpace()) {
                    throw new javax.jms.ResourceAllocationException("Usage Manager memory limit reached. Stopping producer (" + message.getProducerId() + ") to prevent flooding " +getActiveMQDestination().getQualifiedName() + "." +
                            " See http://activemq.apache.org/producer-flow-control.html for more info");
                }
   
                // We can avoid blocking due to low usage if the producer is sending
                // a sync message or
                // if it is using a producer window
                if (producerInfo.getWindowSize() > 0 || message.isResponseRequired()) {
                    // copy the exchange state since the context will be modified while we are waiting
                    // for space.
                    final ProducerBrokerExchange producerExchangeCopy = producerExchange.copy();
                    synchronized (messagesWaitingForSpace) {
                        messagesWaitingForSpace.add(new Runnable() {
                            public void run() {
   
                                try {
                                    // While waiting for space to free up... the
                                    // message may have expired.
                                    if (message.isExpired()) {
                                        broker.messageExpired(context, message);
                                        destinationStatistics.getExpired().increment();
                                    } else {
                                        doMessageSend(producerExchangeCopy, message);
                                    }
   
                                    if (sendProducerAck) {
                                        ProducerAck ack = new ProducerAck(producerInfo.getProducerId(), message.getSize());
                                        context.getConnection().dispatchAsync(ack);
                                    } else {
                                        Response response = new Response();
                                        response.setCorrelationId(message.getCommandId());
                                        context.getConnection().dispatchAsync(response);
                                    }
   
                                } catch (Exception e) {
                                    if (!sendProducerAck && !context.isInRecoveryMode()) {
                                        ExceptionResponse response = new ExceptionResponse(e);
                                        response.setCorrelationId(message.getCommandId());
                                        context.getConnection().dispatchAsync(response);
                                    }
                                }
                            }
                        });
   
                        // If the user manager is not full, then the task will not
                        // get called..
                        if (!memoryUsage.notifyCallbackWhenNotFull(sendMessagesWaitingForSpaceTask)) {
                            // so call it directly here.
                            sendMessagesWaitingForSpaceTask.run();
                        }
                        context.setDontSendReponse(true);
                        return;
                    }
   
                } else {
   
                    // Producer flow control cannot be used, so we have do the flow
                    // control at the broker
                    // by blocking this thread until there is space available.
                    while (!memoryUsage.waitForSpace(1000)) {
                        if (context.getStopping().get()) {
                            throw new IOException("Connection closed, send aborted.");
                        }
                    }
   
                    // The usage manager could have delayed us by the time
                    // we unblock the message could have expired..
                    if (message.isExpired()) {
                        if (LOG.isDebugEnabled()) {
                            LOG.debug("Expired message: " + message);
                        }
                        broker.getRoot().messageExpired(context, message);
                        return;
                    }
                }
            }
        }
        doMessageSend(producerExchange, message);
        if (sendProducerAck) {
            ProducerAck ack = new ProducerAck(producerInfo.getProducerId(), message.getSize());
            context.getConnection().dispatchAsync(ack);
        }
    }

    void doMessageSend(final ProducerBrokerExchange producerExchange, final Message message) throws IOException, Exception {
        final ConnectionContext context = producerExchange.getConnectionContext();
        synchronized (sendLock) {
            if (store != null && message.isPersistent()) {
                if (systemUsage.getStoreUsage().isFull()) {
                    final String logMessage = "Usage Manager Store is Full. Stopping producer (" + message.getProducerId() + ") to prevent flooding " + getActiveMQDestination().getQualifiedName() + "." +
                            " See http://activemq.apache.org/producer-flow-control.html for more info";
                    LOG.info(logMessage);
                    if (systemUsage.isSendFailIfNoSpace()) {
                        throw new javax.jms.ResourceAllocationException(logMessage);
                    }
                }
                while (!systemUsage.getStoreUsage().waitForSpace(1000)) {
                    if (context.getStopping().get()) {
                        throw new IOException(
                                "Connection closed, send aborted.");
                    }
                    LOG.debug(this  + ", waiting for store space... msg: " + message);
                }
                message.getMessageId().setBrokerSequenceId(getDestinationSequenceId());
                store.addMessage(context, message);

            }
        }
        if (context.isInTransaction()) {
            // If this is a transacted message.. increase the usage now so that
            // a big TX does not blow up
            // our memory. This increment is decremented once the tx finishes..
            message.incrementReferenceCount();
            context.getTransaction().addSynchronization(new Synchronization() {
                public void afterCommit() throws Exception {
                    try {
                        // It could take while before we receive the commit
                        // op, by that time the message could have expired..
                        if (broker.isExpired(message)) {
                            broker.messageExpired(context, message);
                            destinationStatistics.getExpired().increment();
                            return;
                        }
                        sendMessage(context, message);
                    } finally {
                        message.decrementReferenceCount();
                    }
                }

                @Override
                public void afterRollback() throws Exception {
                    message.decrementReferenceCount();
                }
            });
        } else {
            // Add to the pending list, this takes care of incrementing the
            // usage manager.
            sendMessage(context, message);
        }
    }
   
    private void expireMessages() {
        if (LOG.isDebugEnabled()) {
            LOG.debug("Expiring messages ..");
        }
       
        // just track the insertion count
        List<Message> browsedMessages = new AbstractList<Message>() {
            int size = 0;

            @Override
            public void add(int index, Message element) {
                size++;
            }

            @Override
            public int size() {
                return size;
            }

            @Override
            public Message get(int index) {
                return null;
            }
        };
        doBrowse(true, browsedMessages, this.getMaxExpirePageSize());
    }

    public void gc(){
    }
   
    public void acknowledge(ConnectionContext context, Subscription sub, MessageAck ack, MessageReference node) throws IOException {
        messageConsumed(context, node);
        if (store != null && node.isPersistent()) {
            // the original ack may be a ranged ack, but we are trying to delete a specific
            // message store here so we need to convert to a non ranged ack.
            if (ack.getMessageCount() > 0) {
                // Dup the ack
                MessageAck a = new MessageAck();
                ack.copy(a);
                ack = a;
                // Convert to non-ranged.
                ack.setFirstMessageId(node.getMessageId());
                ack.setLastMessageId(node.getMessageId());
                ack.setMessageCount(1);
            }
            store.removeMessage(context, ack);
        }
    }

    Message loadMessage(MessageId messageId) throws IOException {
        Message msg = store.getMessage(messageId);
        if (msg != null) {
            msg.setRegionDestination(this);
        }
        return msg;
    }

    public String toString() {
        int size = 0;
        synchronized (messages) {
            size = messages.size();
        }
        return "Queue: destination=" + destination.getPhysicalName() + ", subscriptions=" + consumers.size() + ", memory=" + memoryUsage.getPercentUsage() + "%, size=" + size
               + ", in flight groups=" + messageGroupOwners;
    }

    public void start() throws Exception {
        if (memoryUsage != null) {
            memoryUsage.start();
        }
        systemUsage.getMemoryUsage().addUsageListener(this);
        messages.start();
        if (getExpireMessagesPeriod() > 0) {
            scheduler.schedualPeriodically(expireMessagesTask, getExpireMessagesPeriod());
        }
        doPageIn(false);
    }

    public void stop() throws Exception{
        if (taskRunner != null) {
            taskRunner.shutdown();
        }
        if (this.executor != null) {
            this.executor.shutdownNow();
        }
       
        scheduler.cancel(expireMessagesTask);
       
        if (messages != null) {
            messages.stop();
        }
       
        systemUsage.getMemoryUsage().removeUsageListener(this);
        if (memoryUsage != null) {
            memoryUsage.stop();
        }
        if (store!=null) {
            store.stop();
        }
    }

    // Properties
    // -------------------------------------------------------------------------
    public ActiveMQDestination getActiveMQDestination() {
        return destination;
    }

   
    public MessageGroupMap getMessageGroupOwners() {
        if (messageGroupOwners == null) {
            messageGroupOwners = getMessageGroupMapFactory().createMessageGroupMap();
        }
        return messageGroupOwners;
    }

    public DispatchPolicy getDispatchPolicy() {
        return dispatchPolicy;
    }

    public void setDispatchPolicy(DispatchPolicy dispatchPolicy) {
        this.dispatchPolicy = dispatchPolicy;
    }

    public MessageGroupMapFactory getMessageGroupMapFactory() {
        return messageGroupMapFactory;
    }

    public void setMessageGroupMapFactory(MessageGroupMapFactory messageGroupMapFactory) {
        this.messageGroupMapFactory = messageGroupMapFactory;
    }

    public PendingMessageCursor getMessages() {
        return this.messages;
    }

    public void setMessages(PendingMessageCursor messages) {
        this.messages = messages;
    }
   
    public boolean isUseConsumerPriority() {
        return useConsumerPriority;
    }

    public void setUseConsumerPriority(boolean useConsumerPriority) {
        this.useConsumerPriority = useConsumerPriority;
    }

    public boolean isStrictOrderDispatch() {
        return strictOrderDispatch;
    }

    public void setStrictOrderDispatch(boolean strictOrderDispatch) {
        this.strictOrderDispatch = strictOrderDispatch;
    }
   

    public boolean isOptimizedDispatch() {
        return optimizedDispatch;
    }

    public void setOptimizedDispatch(boolean optimizedDispatch) {
        this.optimizedDispatch = optimizedDispatch;
    }
  public int getTimeBeforeDispatchStarts() {
    return timeBeforeDispatchStarts;
  }

  public void setTimeBeforeDispatchStarts(int timeBeforeDispatchStarts) {
    this.timeBeforeDispatchStarts = timeBeforeDispatchStarts;
  }

  public int getConsumersBeforeDispatchStarts() {
    return consumersBeforeDispatchStarts;
  }

  public void setConsumersBeforeDispatchStarts(int consumersBeforeDispatchStarts) {
    this.consumersBeforeDispatchStarts = consumersBeforeDispatchStarts;
  }

    // Implementation methods
    // -------------------------------------------------------------------------
    private QueueMessageReference createMessageReference(Message message) {
        QueueMessageReference result = new IndirectMessageReference(message);
        return result;
    }

    public Message[] browse() {   
        List<Message> l = new ArrayList<Message>();
        doBrowse(false, l, getMaxBrowsePageSize());
        return l.toArray(new Message[l.size()]);
    }
   
    public void doBrowse(boolean forcePageIn, List<Message> l, int max) {
        final ConnectionContext connectionContext = createConnectionContext();
        try {
            pageInMessages(forcePageIn);
            List<MessageReference> toExpire = new ArrayList<MessageReference>();
            synchronized(dispatchMutex) {
                synchronized (pagedInPendingDispatch) {
                    addAll(pagedInPendingDispatch, l, max, toExpire);
                    for (MessageReference ref : toExpire) {
                        pagedInPendingDispatch.remove(ref);
                        if (broker.isExpired(ref)) {
                            messageExpired(connectionContext, ref);
                        }
                    }
                }
                toExpire.clear();
                synchronized (pagedInMessages) {
                    addAll(pagedInMessages.values(), l, max, toExpire);  
                }
                for (MessageReference ref : toExpire) {
                    if (broker.isExpired(ref)) {
                        messageExpired(connectionContext, ref);
                    } else {
                        synchronized (pagedInMessages) {
                            pagedInMessages.remove(ref.getMessageId());
                        }
                    }
                }
               
                if (l.size() < getMaxBrowsePageSize()) {
                    synchronized (messages) {
                        try {
                            messages.reset();
                            while (messages.hasNext() && l.size() < max) {
                                MessageReference node = messages.next();
                                messages.rollback(node.getMessageId());
                                if (node != null) {
                                    if (broker.isExpired(node)) {
                                        messageExpired(connectionContext,
                                                createMessageReference(node.getMessage()));
                                    } else if (l.contains(node.getMessage()) == false) {
                                        l.add(node.getMessage());
                                    }
                                }
                            }
                        } finally {
                            messages.release();
                        }
                    }
                }
            }
        } catch (Exception e) {
            LOG.error("Problem retrieving message for browse", e);
        }
    }

    private void addAll(Collection<QueueMessageReference> refs,
            List<Message> l, int maxBrowsePageSize, List<MessageReference> toExpire) throws Exception {
        for (Iterator<QueueMessageReference> i = refs.iterator(); i.hasNext()
                && l.size() < getMaxBrowsePageSize();) {
            QueueMessageReference ref = i.next();
            if (ref.isExpired()) {
                toExpire.add(ref);
            } else if (l.contains(ref.getMessage()) == false) {
                l.add(ref.getMessage());
            }
        }
    }

    public Message getMessage(String id) {
        MessageId msgId = new MessageId(id);
        try {
            synchronized (pagedInMessages) {
                QueueMessageReference r = this.pagedInMessages.get(msgId);
                if (r != null) {
                    return r.getMessage();
                }
            }
            synchronized (messages) {
                try {
                    messages.reset();
                    while (messages.hasNext()) {
                        try {
                            MessageReference r = messages.next();
                            messages.rollback(r.getMessageId());
                            if (msgId.equals(r.getMessageId())) {
                                Message m = r.getMessage();
                                if (m != null) {
                                    return m;
                                }
                                break;
                            }
                        } catch (IOException e) {
                            LOG.error("got an exception retrieving message "
                                    + id);
                        }
                    }
                } finally {
                    messages.release();
                }
            }
        } catch (IOException e) {
            LOG.error("got an exception retrieving message " + id);
        }
        return null;
    }

    public void purge() throws Exception {  
        ConnectionContext c = createConnectionContext();
        List<MessageReference> list = null;
        do {
            pageInMessages();
            synchronized (pagedInMessages) {
                list = new ArrayList<MessageReference>(pagedInMessages.values());
            }

            for (MessageReference ref : list) {
                try {
                    QueueMessageReference r = (QueueMessageReference) ref;
                        removeMessage(c,(IndirectMessageReference) r);
                } catch (IOException e) {
                }
            }
        } while (!pagedInMessages.isEmpty() || this.destinationStatistics.getMessages().getCount() > 0);
        gc();
        this.destinationStatistics.getMessages().setCount(0);
        getMessages().clear();
    }

    /**
     * Removes the message matching the given messageId
     */
    public boolean removeMessage(String messageId) throws Exception {
        return removeMatchingMessages(createMessageIdFilter(messageId), 1) > 0;
    }

    /**
     * Removes the messages matching the given selector
     *
     * @return the number of messages removed
     */
    public int removeMatchingMessages(String selector) throws Exception {
        return removeMatchingMessages(selector, -1);
    }

    /**
     * Removes the messages matching the given selector up to the maximum number
     * of matched messages
     *
     * @return the number of messages removed
     */
    public int removeMatchingMessages(String selector, int maximumMessages) throws Exception {
        return removeMatchingMessages(createSelectorFilter(selector), maximumMessages);
    }

    /**
     * Removes the messages matching the given filter up to the maximum number
     * of matched messages
     *
     * @return the number of messages removed
     */
    public int removeMatchingMessages(MessageReferenceFilter filter, int maximumMessages) throws Exception {
        int movedCounter = 0;
        Set<MessageReference> set = new CopyOnWriteArraySet<MessageReference>();
        ConnectionContext context = createConnectionContext();
        do {
            pageInMessages();
            synchronized (pagedInMessages) {
                set.addAll(pagedInMessages.values());
            }
            List <MessageReference>list = new ArrayList<MessageReference>(set);
            for (MessageReference ref : list) {
                IndirectMessageReference r = (IndirectMessageReference) ref;
                if (filter.evaluate(context, r)) {

                    removeMessage(context, r);
                    set.remove(r);
                    if (++movedCounter >= maximumMessages
                            && maximumMessages > 0) {
                        return movedCounter;
                    }
                }
            }
        } while (set.size() < this.destinationStatistics.getMessages().getCount());
        return movedCounter;
    }

    /**
     * Copies the message matching the given messageId
     */
    public boolean copyMessageTo(ConnectionContext context, String messageId, ActiveMQDestination dest) throws Exception {
        return copyMatchingMessages(context, createMessageIdFilter(messageId), dest, 1) > 0;
    }

    /**
     * Copies the messages matching the given selector
     *
     * @return the number of messages copied
     */
    public int copyMatchingMessagesTo(ConnectionContext context, String selector, ActiveMQDestination dest) throws Exception {
        return copyMatchingMessagesTo(context, selector, dest, -1);
    }

    /**
     * Copies the messages matching the given selector up to the maximum number
     * of matched messages
     *
     * @return the number of messages copied
     */
    public int copyMatchingMessagesTo(ConnectionContext context, String selector, ActiveMQDestination dest, int maximumMessages) throws Exception {
        return copyMatchingMessages(context, createSelectorFilter(selector), dest, maximumMessages);
    }

    /**
     * Copies the messages matching the given filter up to the maximum number of
     * matched messages
     *
     * @return the number of messages copied
     */
    public int copyMatchingMessages(ConnectionContext context, MessageReferenceFilter filter, ActiveMQDestination dest, int maximumMessages) throws Exception {
        int movedCounter = 0;
        int count = 0;
        Set<MessageReference> set = new CopyOnWriteArraySet<MessageReference>();
        do {
            int oldMaxSize=getMaxPageSize();
            setMaxPageSize((int) this.destinationStatistics.getMessages().getCount());
            pageInMessages();
            setMaxPageSize(oldMaxSize);
            synchronized (pagedInMessages) {
                set.addAll(pagedInMessages.values());
            }
            List <MessageReference>list = new ArrayList<MessageReference>(set);
            for (MessageReference ref : list) {
                IndirectMessageReference r = (IndirectMessageReference) ref;
                if (filter.evaluate(context, r)) {
                   
                    r.incrementReferenceCount();                   
                    try {
                        Message m = r.getMessage();
                        BrokerSupport.resend(context, m, dest);
                        if (++movedCounter >= maximumMessages
                                && maximumMessages > 0) {
                            return movedCounter;
                        }
                    } finally {
                        r.decrementReferenceCount();
                    }
                }
                count++;
            }
        } while (count < this.destinationStatistics.getMessages().getCount());
        return movedCounter;
    }
   
    /**
     * Move a message
     * @param context connection context
     * @param m message
     * @param dest ActiveMQDestination
     * @throws Exception
     */
    public boolean moveMessageTo(ConnectionContext context,Message m,ActiveMQDestination dest) throws Exception {
        QueueMessageReference r = createMessageReference(m);
        BrokerSupport.resend(context, m, dest);
        removeMessage(context, r);
        synchronized (messages) {
            messages.rollback(r.getMessageId());
        }
        return true;
    }

    /**
     * Moves the message matching the given messageId
     */
    public boolean moveMessageTo(ConnectionContext context, String messageId, ActiveMQDestination dest) throws Exception {
        return moveMatchingMessagesTo(context, createMessageIdFilter(messageId), dest, 1) > 0;
    }

    /**
     * Moves the messages matching the given selector
     *
     * @return the number of messages removed
     */
    public int moveMatchingMessagesTo(ConnectionContext context, String selector, ActiveMQDestination dest) throws Exception {
        return moveMatchingMessagesTo(context, selector, dest,Integer.MAX_VALUE);
    }

    /**
     * Moves the messages matching the given selector up to the maximum number
     * of matched messages
     */
    public int moveMatchingMessagesTo(ConnectionContext context, String selector, ActiveMQDestination dest, int maximumMessages) throws Exception {
        return moveMatchingMessagesTo(context, createSelectorFilter(selector), dest, maximumMessages);
    }

    /**
     * Moves the messages matching the given filter up to the maximum number of
     * matched messages
     */
    public int moveMatchingMessagesTo(ConnectionContext context,
            MessageReferenceFilter filter, ActiveMQDestination dest,
            int maximumMessages) throws Exception {
        int movedCounter = 0;
        Set<MessageReference> set = new CopyOnWriteArraySet<MessageReference>();
        do {
            doPageIn(true);
            synchronized (pagedInMessages) {
                set.addAll(pagedInMessages.values());
            }
            List<MessageReference> list = new ArrayList<MessageReference>(set);
            for (MessageReference ref : list) {
                IndirectMessageReference r = (IndirectMessageReference) ref;
                if (filter.evaluate(context, r)) {
                    // We should only move messages that can be locked.
                    moveMessageTo(context, ref.getMessage(), dest);
                    set.remove(r);
                    if (++movedCounter >= maximumMessages
                            && maximumMessages > 0) {
                        return movedCounter;
                    }
                }
            }
        } while (set.size() < this.destinationStatistics.getMessages().getCount()
                && set.size() < maximumMessages);
        return movedCounter;
    }
   
    BrowserDispatch getNextBrowserDispatch() {
        synchronized (pagedInMessages) {
            if( browserDispatches.isEmpty() ) {
                return null;
            }
            return browserDispatches.removeFirst();
        }

    }

    /**
     * @return true if we would like to iterate again
     * @see org.apache.activemq.thread.Task#iterate()
     */
    public boolean iterate() {
        boolean pageInMoreMessages = false;  
        synchronized(iteratingMutex) {
           
            // do early to allow dispatch of these waiting messages
            synchronized(messagesWaitingForSpace) {
                while (!messagesWaitingForSpace.isEmpty() && !memoryUsage.isFull()) {
                    Runnable op = messagesWaitingForSpace.removeFirst();
                    op.run();
                }
            }
           
            BrowserDispatch rd;
          while ((rd = getNextBrowserDispatch()) != null) {
              pageInMoreMessages = true;
             
              try {
                  MessageEvaluationContext msgContext = new NonCachedMessageEvaluationContext();
                  msgContext.setDestination(destination);
     
                  QueueBrowserSubscription browser = rd.getBrowser();
                  for (QueueMessageReference node : rd.messages) {
                      if (!node.isAcked()) {
                          msgContext.setMessageReference(node);
                          if (browser.matches(node, msgContext)) {
                              browser.add(node);
                          }
                      }
                  }
                                     
                    rd.done();

              } catch (Exception e) {
                  LOG.warn("exception on dispatch to browser: " + rd.getBrowser(), e);
              }
          }
         
          if (firstConsumer) {
            firstConsumer = false;
            try {
              if (consumersBeforeDispatchStarts > 0) {
                int timeout = 1000; // wait one second by default if consumer count isn't reached 
                if (timeBeforeDispatchStarts > 0) {
                  timeout = timeBeforeDispatchStarts;
                }
                if (consumersBeforeStartsLatch.await(timeout, TimeUnit.MILLISECONDS)) {
                  if (LOG.isDebugEnabled()) {
                    LOG.debug(consumers.size() + " consumers subscribed. Starting dispatch.");
                  }
                } else {
                  if (LOG.isDebugEnabled()) {
                    LOG.debug(timeout + " ms elapsed and " +  consumers.size() + " consumers subscribed. Starting dispatch.");
                  }
                }
              }             
              if (timeBeforeDispatchStarts > 0 && consumersBeforeDispatchStarts <= 0) {
                iteratingMutex.wait(timeBeforeDispatchStarts);
                if (LOG.isDebugEnabled()) {
                  LOG.debug(timeBeforeDispatchStarts + " ms elapsed. Starting dispatch.");
                }
              }
            } catch (Exception e) {
              LOG.error(e);
            }
          }
         
          synchronized (messages) {
              pageInMoreMessages |= !messages.isEmpty();
          }              
         
          // Kinda ugly.. but I think dispatchLock is the only mutex protecting the
          // pagedInPendingDispatch variable.          
          synchronized(dispatchMutex) {
              pageInMoreMessages |= !pagedInPendingDispatch.isEmpty();
          }
         
          // Perhaps we should page always into the pagedInPendingDispatch list is
          // !messages.isEmpty(), and then if !pagedInPendingDispatch.isEmpty()
          // then we do a dispatch.
          if (pageInMoreMessages) {
              try {
                 pageInMessages(false);
                
              } catch (Throwable e) {
                  LOG.error("Failed to page in more queue messages ", e);
                }
          }
          return !messagesWaitingForSpace.isEmpty();
        }
    }

    protected MessageReferenceFilter createMessageIdFilter(final String messageId) {
        return new MessageReferenceFilter() {
            public boolean evaluate(ConnectionContext context, MessageReference r) {
                return messageId.equals(r.getMessageId().toString());
            }
            public String toString() {
                return "MessageIdFilter: "+messageId;
            }
        };
    }

    protected MessageReferenceFilter createSelectorFilter(String selector) throws InvalidSelectorException {
        final BooleanExpression selectorExpression = SelectorParser.parse(selector);

        return new MessageReferenceFilter() {
            public boolean evaluate(ConnectionContext context, MessageReference r) throws JMSException {
                MessageEvaluationContext messageEvaluationContext = context.getMessageEvaluationContext();

                messageEvaluationContext.setMessageReference(r);
                if (messageEvaluationContext.getDestination() == null) {
                    messageEvaluationContext.setDestination(getActiveMQDestination());
                }

                return selectorExpression.matches(messageEvaluationContext);
            }
        };
    }

    protected void removeMessage(ConnectionContext c, QueueMessageReference r) throws IOException {
        removeMessage(c, null, r);
    }
   
    protected void removeMessage(ConnectionContext c, Subscription subs,QueueMessageReference r) throws IOException {
        MessageAck ack = new MessageAck();
        ack.setAckType(MessageAck.STANDARD_ACK_TYPE);
        ack.setDestination(destination);
        ack.setMessageID(r.getMessageId());
        removeMessage(c, subs, r, ack);
    }
   
    protected void removeMessage(ConnectionContext context,Subscription sub,final QueueMessageReference reference,MessageAck ack) throws IOException {
        reference.setAcked(true);
        // This sends the ack the the journal..
        if (!ack.isInTransaction()) {
            acknowledge(context, sub, ack, reference);
            getDestinationStatistics().getDequeues().increment();
            dropMessage(reference);
        } else {
            try {
                acknowledge(context, sub, ack, reference);
            } finally {
                context.getTransaction().addSynchronization(new Synchronization() {
               
                    public void afterCommit() throws Exception {
                        getDestinationStatistics().getDequeues().increment();
                        dropMessage(reference);
                        wakeup();
                    }
               
                    public void afterRollback() throws Exception {
                        reference.setAcked(false);
                    }
                });
            }
        }
        if (ack.isPoisonAck()) {
            // message gone to DLQ, is ok to allow redelivery
            synchronized(messages) {
                messages.rollback(reference.getMessageId());
            }
        }

    }
   
    private void dropMessage(QueueMessageReference reference) {
        reference.drop();
        destinationStatistics.getMessages().decrement();
        synchronized(pagedInMessages) {
            pagedInMessages.remove(reference.getMessageId());
        }
    }
   
    public void messageExpired(ConnectionContext context,MessageReference reference) {
        messageExpired(context,null,reference);
    }
   
    public void messageExpired(ConnectionContext context,Subscription subs, MessageReference reference) {
        if (LOG.isDebugEnabled()) {     
            LOG.debug("message expired: " + reference);
        }
        broker.messageExpired(context, reference);
        destinationStatistics.getExpired().increment();
        try {
            removeMessage(context,subs,(QueueMessageReference)reference);
        } catch (IOException e) {
            LOG.error("Failed to remove expired Message from the store ",e);
        }
        asyncWakeup();
    }
   
    protected ConnectionContext createConnectionContext() {
        ConnectionContext answer = new ConnectionContext(new NonCachedMessageEvaluationContext());
        answer.setBroker(this.broker);
        answer.getMessageEvaluationContext().setDestination(getActiveMQDestination());
        return answer;
    }

    final void sendMessage(final ConnectionContext context, Message msg) throws Exception {
        if (!msg.isPersistent() && messages.getSystemUsage() != null) {
          if (systemUsage.getTempUsage().isFull()) {
                final String logMessage = "Usage Manager Temp Store is Full. Stopping producer (" + msg.getProducerId() + ") to prevent flooding " + getActiveMQDestination().getQualifiedName() + "." +
                        " See http://activemq.apache.org/producer-flow-control.html for more info";
                LOG.info(logMessage);
                if (systemUsage.isSendFailIfNoSpace()) {
                    throw new javax.jms.ResourceAllocationException(logMessage);
                }
            }
            messages.getSystemUsage().getTempUsage().waitForSpace();
        }
        synchronized(messages) {
            messages.addMessageLast(msg);
        }
        destinationStatistics.getEnqueues().increment();
        destinationStatistics.getMessages().increment();
        messageDelivered(context, msg);
        synchronized (consumers) {
            if (consumers.isEmpty()) {
                onMessageWithNoConsumers(context, msg);
            }
        }
        wakeup();
    }
   
    public void wakeup() {
        if (optimizedDispatch || isSlave()) {
            iterate();
        } else {
            asyncWakeup();
        }
    }
   
    public void asyncWakeup() {
        try {
            this.taskRunner.wakeup();
        } catch (InterruptedException e) {
            LOG.warn("Async task tunner failed to wakeup ", e);
        }
    }
 
    private boolean isSlave() {
        return broker.getBrokerService().isSlave();
    }

    private List<QueueMessageReference> doPageIn(boolean force) throws Exception {
        List<QueueMessageReference> result = null;
        List<QueueMessageReference> resultList = null;
        synchronized(dispatchMutex) {
            int toPageIn = Math.min(getMaxPageSize(), messages.size());
            if (LOG.isDebugEnabled()) {
                LOG.debug(destination.getPhysicalName() + " toPageIn: "  + toPageIn + ", Inflight: "
                        + destinationStatistics.getInflight().getCount()
                        + ", pagedInMessages.size " + pagedInMessages.size());
            }
          
            if (isLazyDispatch()&& !force) {
                // Only page in the minimum number of messages which can be dispatched immediately.
                toPageIn = Math.min(getConsumerMessageCountBeforeFull(), toPageIn);
            }
           
            if ((force || !consumers.isEmpty()) && toPageIn > 0) {
                int count = 0;
                result = new ArrayList<QueueMessageReference>(toPageIn);
                synchronized (messages) {
                    try {
                        messages.setMaxBatchSize(toPageIn);
                        messages.reset();
                        while (messages.hasNext() && count < toPageIn) {
                            MessageReference node = messages.next();
                            node.incrementReferenceCount();
                            messages.remove();
                            QueueMessageReference ref = createMessageReference(node.getMessage());
                            if (!broker.isExpired(node)) {
                                result.add(ref);
                                count++;
                            } else {
                                messageExpired(createConnectionContext(), ref);
                            }
                        }
                    } finally {
                        messages.release();
                    }
                }
                // Only add new messages, not already pagedIn to avoid multiple dispatch attempts
                synchronized (pagedInMessages) {
                    resultList = new ArrayList<QueueMessageReference>(result.size());
                    for(QueueMessageReference ref : result) {
                        if (!pagedInMessages.containsKey(ref.getMessageId())) {
                            pagedInMessages.put(ref.getMessageId(), ref);
                            resultList.add(ref);
                        }
                    }
                }
            } else {
                // Avoid return null list, if condition is not validated
                resultList = new ArrayList<QueueMessageReference>();
            }
        }
        return resultList;
    }

    private void doDispatch(List<QueueMessageReference> list) throws Exception {
        boolean doWakeUp = false;
        synchronized(dispatchMutex) {
      
            synchronized (pagedInPendingDispatch) {
                if (!pagedInPendingDispatch.isEmpty()) {
                    // Try to first dispatch anything that had not been
                    // dispatched before.
                    pagedInPendingDispatch = doActualDispatch(pagedInPendingDispatch);
                }
                // and now see if we can dispatch the new stuff.. and append to
                // the pending
                // list anything that does not actually get dispatched.
                if (list != null && !list.isEmpty()) {
                    if (pagedInPendingDispatch.isEmpty()) {
                        pagedInPendingDispatch.addAll(doActualDispatch(list));
                    } else {
                        for (QueueMessageReference qmr : list) {
                            if (!pagedInPendingDispatch.contains(qmr)) {
                                pagedInPendingDispatch.add(qmr);
                            }
                        }
                        doWakeUp  = true;
                    }
                }
            }
        }
        if (doWakeUp) {
            wakeup();
        }
    }
   
    /**
     * @return list of messages that could get dispatched to consumers if they
     *         were not full.
     */
    private List<QueueMessageReference> doActualDispatch(List<QueueMessageReference> list) throws Exception {
        List<Subscription> consumers;
       
        synchronized (this.consumers) {
            if (this.consumers.isEmpty() || isSlave()) {
                // slave dispatch happens in processDispatchNotification
                return list;
            }
            consumers = new ArrayList<Subscription>(this.consumers);
        }

        List<QueueMessageReference> rc = new ArrayList<QueueMessageReference>(list.size());
        Set<Subscription> fullConsumers = new HashSet<Subscription>(this.consumers.size());
       
        for (MessageReference node : list) {
            Subscription target = null;
            int interestCount=0;
            for (Subscription s : consumers) {
              if (s instanceof QueueBrowserSubscription) {
                interestCount++;
                continue;
              }
                if (dispatchSelector.canSelect(s, node)) {
                    if (!fullConsumers.contains(s)) {
                        if (!s.isFull()) {
                            // Dispatch it.
                            s.add(node);
                            target = s;
                            break;
                        } else {
                            // no further dispatch of list to a full consumer to avoid out of order message receipt
                            fullConsumers.add(s);
                        }
                    }
                    interestCount++;
                } else {
                  // makes sure it gets dispatched again
                  if (!node.isDropped() && !((QueueMessageReference)node).isAcked() && (!node.isDropped() || s.getConsumerInfo().isBrowser())) {
                    interestCount++;
                  }
                }
            }
           
            if ((target == null && interestCount>0) || consumers.size() == 0) {
                // This means all subs were full or that there are no consumers...
                rc.add((QueueMessageReference)node);
            }

            // If it got dispatched, rotate the consumer list to get round robin distribution.
            if (target != null && !strictOrderDispatch && consumers.size() > 1 &&
                    !dispatchSelector.isExclusiveConsumer(target)) {
                synchronized (this.consumers) {
                    if( removeFromConsumerList(target) ) {
                        addToConsumerList(target);
                        consumers = new ArrayList<Subscription>(this.consumers);
                    }
                }
            }
        }

       
        return rc;
    }

    private void pageInMessages() throws Exception {
        pageInMessages(true);
    }

    protected void pageInMessages(boolean force) throws Exception {
            doDispatch(doPageIn(force));
    }
   
    private void addToConsumerList(Subscription sub) {
        if (useConsumerPriority) {
            consumers.add(sub);
            Collections.sort(consumers, orderedCompare);
        } else {
            consumers.add(sub);
        }
    }
   
    private boolean removeFromConsumerList(Subscription sub) {
        return consumers.remove(sub);
    }
   
    private int getConsumerMessageCountBeforeFull() throws Exception {
        int total = 0;
        boolean zeroPrefetch = false;
        synchronized (consumers) {
            for (Subscription s : consumers) {
              zeroPrefetch |= s.getPrefetchSize() == 0;
              int countBeforeFull = s.countBeforeFull();
                total += countBeforeFull;
            }
        }
        if (total==0 && zeroPrefetch){
          total=1;
        }
        return total;
    }

    /*
     * In slave mode, dispatch is ignored till we get this notification as the dispatch
     * process is non deterministic between master and slave.
     * On a notification, the actual dispatch to the subscription (as chosen by the master)
     * is completed.
     * (non-Javadoc)
     * @see org.apache.activemq.broker.region.BaseDestination#processDispatchNotification(org.apache.activemq.command.MessageDispatchNotification)
     */
    public void processDispatchNotification(
            MessageDispatchNotification messageDispatchNotification) throws Exception {
        // do dispatch
        Subscription sub = getMatchingSubscription(messageDispatchNotification);
        if (sub != null) {
            MessageReference message = getMatchingMessage(messageDispatchNotification);
            sub.add(message);  
            sub.processMessageDispatchNotification(messageDispatchNotification);
        }
    }

    private QueueMessageReference getMatchingMessage(MessageDispatchNotification messageDispatchNotification) throws Exception {
        QueueMessageReference message = null;
        MessageId messageId = messageDispatchNotification.getMessageId();
       
       synchronized(dispatchMutex) {
            synchronized (pagedInPendingDispatch) {
               for(QueueMessageReference ref : pagedInPendingDispatch) {
                   if (messageId.equals(ref.getMessageId())) {
                       message = ref;
                       pagedInPendingDispatch.remove(ref);
                       break;
                   }
               }
            }
   
            if (message == null) {
                synchronized (pagedInMessages) {
                    message = pagedInMessages.get(messageId);
                }
            }
           
            if (message == null) {           
                synchronized (messages) {
                    try {
                        messages.setMaxBatchSize(getMaxPageSize());
                        messages.reset();
                        while (messages.hasNext()) {
                            MessageReference node = messages.next();
                            node.incrementReferenceCount();
                            messages.remove();
                            if (messageId.equals(node.getMessageId())) {
                                message = this.createMessageReference(node.getMessage());
                                break;
                            }
                        }
                    } finally {
                        messages.release();
                    }
                }
            }
           
            if (message == null) {
                Message msg = loadMessage(messageId);
                if (msg != null) {
                    message = this.createMessageReference(msg);
                }
            }         
           
        }
        if (message == null) {
            throw new JMSException(
                    "Slave broker out of sync with master - Message: "
                    + messageDispatchNotification.getMessageId()
                    + " on " + messageDispatchNotification.getDestination()
                    + " does not exist among pending(" + pagedInPendingDispatch.size() + ") for subscription: "
                    + messageDispatchNotification.getConsumerId());
        }
        return message;
    }

    /**
     * Find a consumer that matches the id in the message dispatch notification
     * @param messageDispatchNotification
     * @return sub or null if the subscription has been removed before dispatch
     * @throws JMSException
     */
    private Subscription getMatchingSubscription(MessageDispatchNotification messageDispatchNotification) throws JMSException {
        Subscription sub = null;
        synchronized (consumers) {
            for (Subscription s : consumers) {
                if (messageDispatchNotification.getConsumerId().equals(s.getConsumerInfo().getConsumerId())) {
                    sub = s;
                    break;
                }
            }
        }
        return sub;
    }

    public void onUsageChanged(Usage usage, int oldPercentUsage, int newPercentUsage) {
        if (oldPercentUsage > newPercentUsage) {
            asyncWakeup();
        }
    }
}
TOP

Related Classes of org.apache.activemq.broker.region.Queue

TOP
Copyright © 2018 www.massapi.com. All rights reserved.
All source code are property of their respective owners. Java is a trademark of Sun Microsystems, Inc and owned by ORACLE Inc. Contact coftware#gmail.com.