001/**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.activemq.broker.region;
018
019import java.io.IOException;
020import java.util.ArrayList;
021import java.util.LinkedList;
022import java.util.List;
023import java.util.concurrent.atomic.AtomicLong;
024
025import javax.jms.JMSException;
026
027import org.apache.activemq.ActiveMQMessageAudit;
028import org.apache.activemq.broker.Broker;
029import org.apache.activemq.broker.ConnectionContext;
030import org.apache.activemq.broker.region.cursors.FilePendingMessageCursor;
031import org.apache.activemq.broker.region.cursors.PendingMessageCursor;
032import org.apache.activemq.broker.region.cursors.VMPendingMessageCursor;
033import org.apache.activemq.broker.region.policy.MessageEvictionStrategy;
034import org.apache.activemq.broker.region.policy.OldestMessageEvictionStrategy;
035import org.apache.activemq.command.ConsumerControl;
036import org.apache.activemq.command.ConsumerInfo;
037import org.apache.activemq.command.Message;
038import org.apache.activemq.command.MessageAck;
039import org.apache.activemq.command.MessageDispatch;
040import org.apache.activemq.command.MessageDispatchNotification;
041import org.apache.activemq.command.MessageId;
042import org.apache.activemq.command.MessagePull;
043import org.apache.activemq.command.Response;
044import org.apache.activemq.thread.Scheduler;
045import org.apache.activemq.transaction.Synchronization;
046import org.apache.activemq.transport.TransmitCallback;
047import org.apache.activemq.usage.SystemUsage;
048import org.slf4j.Logger;
049import org.slf4j.LoggerFactory;
050
051public class TopicSubscription extends AbstractSubscription {
052
053    private static final Logger LOG = LoggerFactory.getLogger(TopicSubscription.class);
054    private static final AtomicLong CURSOR_NAME_COUNTER = new AtomicLong(0);
055
056    protected PendingMessageCursor matched;
057    protected final SystemUsage usageManager;
058    boolean singleDestination = true;
059    Destination destination;
060    private final Scheduler scheduler;
061
062    private int maximumPendingMessages = -1;
063    private MessageEvictionStrategy messageEvictionStrategy = new OldestMessageEvictionStrategy();
064    private int discarded;
065    private final Object matchedListMutex = new Object();
066    private int memoryUsageHighWaterMark = 95;
067    // allow duplicate suppression in a ring network of brokers
068    protected int maxProducersToAudit = 1024;
069    protected int maxAuditDepth = 1000;
070    protected boolean enableAudit = false;
071    protected ActiveMQMessageAudit audit;
072    protected boolean active = false;
073    protected boolean discarding = false;
074
075    //Used for inflight message size calculations
076    protected final Object dispatchLock = new Object();
077    protected final List<MessageReference> dispatched = new ArrayList<MessageReference>();
078
079    public TopicSubscription(Broker broker,ConnectionContext context, ConsumerInfo info, SystemUsage usageManager) throws Exception {
080        super(broker, context, info);
081        this.usageManager = usageManager;
082        String matchedName = "TopicSubscription:" + CURSOR_NAME_COUNTER.getAndIncrement() + "[" + info.getConsumerId().toString() + "]";
083        if (info.getDestination().isTemporary() || broker.getTempDataStore()==null ) {
084            this.matched = new VMPendingMessageCursor(false);
085        } else {
086            this.matched = new FilePendingMessageCursor(broker,matchedName,false);
087        }
088
089        this.scheduler = broker.getScheduler();
090    }
091
092    public void init() throws Exception {
093        this.matched.setSystemUsage(usageManager);
094        this.matched.setMemoryUsageHighWaterMark(getCursorMemoryHighWaterMark());
095        this.matched.start();
096        if (enableAudit) {
097            audit= new ActiveMQMessageAudit(maxAuditDepth, maxProducersToAudit);
098        }
099        this.active=true;
100    }
101
102    @Override
103    public void add(MessageReference node) throws Exception {
104        if (isDuplicate(node)) {
105            return;
106        }
107        // Lets use an indirect reference so that we can associate a unique
108        // locator /w the message.
109        node = new IndirectMessageReference(node.getMessage());
110        getSubscriptionStatistics().getEnqueues().increment();
111        synchronized (matchedListMutex) {
112            // if this subscriber is already discarding a message, we don't want to add
113            // any more messages to it as those messages can only be advisories generated in the process,
114            // which can trigger the recursive call loop
115            if (discarding) return;
116
117            if (!isFull() && matched.isEmpty()) {
118                // if maximumPendingMessages is set we will only discard messages which
119                // have not been dispatched (i.e. we allow the prefetch buffer to be filled)
120                dispatch(node);
121                setSlowConsumer(false);
122            } else {
123                if (info.getPrefetchSize() > 1 && matched.size() > info.getPrefetchSize()) {
124                    // Slow consumers should log and set their state as such.
125                    if (!isSlowConsumer()) {
126                        LOG.warn("{}: has twice its prefetch limit pending, without an ack; it appears to be slow", toString());
127                        setSlowConsumer(true);
128                        for (Destination dest: destinations) {
129                            dest.slowConsumer(getContext(), this);
130                        }
131                    }
132                }
133                if (maximumPendingMessages != 0) {
134                    boolean warnedAboutWait = false;
135                    while (active) {
136                        while (matched.isFull()) {
137                            if (getContext().getStopping().get()) {
138                                LOG.warn("{}: stopped waiting for space in pendingMessage cursor for: {}", toString(), node.getMessageId());
139                                getSubscriptionStatistics().getEnqueues().decrement();
140                                return;
141                            }
142                            if (!warnedAboutWait) {
143                                LOG.info("{}: Pending message cursor [{}] is full, temp usag ({}%) or memory usage ({}%) limit reached, blocking message add() pending the release of resources.",
144                                        new Object[]{
145                                                toString(),
146                                                matched,
147                                                matched.getSystemUsage().getTempUsage().getPercentUsage(),
148                                                matched.getSystemUsage().getMemoryUsage().getPercentUsage()
149                                        });
150                                warnedAboutWait = true;
151                            }
152                            matchedListMutex.wait(20);
153                        }
154                        // Temporary storage could be full - so just try to add the message
155                        // see https://issues.apache.org/activemq/browse/AMQ-2475
156                        if (matched.tryAddMessageLast(node, 10)) {
157                            break;
158                        }
159                    }
160                    if (maximumPendingMessages > 0) {
161                        // calculate the high water mark from which point we
162                        // will eagerly evict expired messages
163                        int max = messageEvictionStrategy.getEvictExpiredMessagesHighWatermark();
164                        if (maximumPendingMessages > 0 && maximumPendingMessages < max) {
165                            max = maximumPendingMessages;
166                        }
167                        if (!matched.isEmpty() && matched.size() > max) {
168                            removeExpiredMessages();
169                        }
170                        // lets discard old messages as we are a slow consumer
171                        while (!matched.isEmpty() && matched.size() > maximumPendingMessages) {
172                            int pageInSize = matched.size() - maximumPendingMessages;
173                            // only page in a 1000 at a time - else we could blow the memory
174                            pageInSize = Math.max(1000, pageInSize);
175                            LinkedList<MessageReference> list = null;
176                            MessageReference[] oldMessages=null;
177                            synchronized(matched){
178                                list = matched.pageInList(pageInSize);
179                                oldMessages = messageEvictionStrategy.evictMessages(list);
180                                for (MessageReference ref : list) {
181                                    ref.decrementReferenceCount();
182                                }
183                            }
184                            int messagesToEvict = 0;
185                            if (oldMessages != null){
186                                messagesToEvict = oldMessages.length;
187                                for (int i = 0; i < messagesToEvict; i++) {
188                                    MessageReference oldMessage = oldMessages[i];
189                                    discard(oldMessage);
190                                }
191                            }
192                            // lets avoid an infinite loop if we are given a bad eviction strategy
193                            // for a bad strategy lets just not evict
194                            if (messagesToEvict == 0) {
195                                LOG.warn("No messages to evict returned for {} from eviction strategy: {} out of {} candidates", new Object[]{
196                                        destination, messageEvictionStrategy, list.size()
197                                });
198                                break;
199                            }
200                        }
201                    }
202                    dispatchMatched();
203                }
204            }
205        }
206    }
207
208    private boolean isDuplicate(MessageReference node) {
209        boolean duplicate = false;
210        if (enableAudit && audit != null) {
211            duplicate = audit.isDuplicate(node);
212            if (LOG.isDebugEnabled()) {
213                if (duplicate) {
214                    LOG.debug("{}, ignoring duplicate add: {}", this, node.getMessageId());
215                }
216            }
217        }
218        return duplicate;
219    }
220
221    /**
222     * Discard any expired messages from the matched list. Called from a
223     * synchronized block.
224     *
225     * @throws IOException
226     */
227    protected void removeExpiredMessages() throws IOException {
228        try {
229            matched.reset();
230            while (matched.hasNext()) {
231                MessageReference node = matched.next();
232                node.decrementReferenceCount();
233                if (node.isExpired()) {
234                    matched.remove();
235                    getSubscriptionStatistics().getDispatched().increment();
236                    node.decrementReferenceCount();
237                    if (broker.isExpired(node)) {
238                        ((Destination) node.getRegionDestination()).getDestinationStatistics().getExpired().increment();
239                        broker.messageExpired(getContext(), node, this);
240                    }
241                    break;
242                }
243            }
244        } finally {
245            matched.release();
246        }
247    }
248
249    @Override
250    public void processMessageDispatchNotification(MessageDispatchNotification mdn) {
251        synchronized (matchedListMutex) {
252            try {
253                matched.reset();
254                while (matched.hasNext()) {
255                    MessageReference node = matched.next();
256                    node.decrementReferenceCount();
257                    if (node.getMessageId().equals(mdn.getMessageId())) {
258                        synchronized(dispatchLock) {
259                            matched.remove();
260                            getSubscriptionStatistics().getDispatched().increment();
261                            dispatched.add(node);
262                            getSubscriptionStatistics().getInflightMessageSize().addSize(node.getSize());
263                            node.decrementReferenceCount();
264                        }
265                        break;
266                    }
267                }
268            } finally {
269                matched.release();
270            }
271        }
272    }
273
274    @Override
275    public synchronized void acknowledge(final ConnectionContext context, final MessageAck ack) throws Exception {
276        super.acknowledge(context, ack);
277
278        if (ack.isStandardAck()) {
279            updateStatsOnAck(context, ack);
280        } else if (ack.isPoisonAck()) {
281            if (ack.isInTransaction()) {
282                throw new JMSException("Poison ack cannot be transacted: " + ack);
283            }
284            updateStatsOnAck(context, ack);
285            contractPrefetchExtension(ack.getMessageCount());
286        } else if (ack.isIndividualAck()) {
287            updateStatsOnAck(context, ack);
288            if (ack.isInTransaction()) {
289                expandPrefetchExtension(1);
290            }
291        } else if (ack.isExpiredAck()) {
292            updateStatsOnAck(ack);
293            contractPrefetchExtension(ack.getMessageCount());
294        } else if (ack.isDeliveredAck()) {
295            // Message was delivered but not acknowledged: update pre-fetch counters.
296           expandPrefetchExtension(ack.getMessageCount());
297        } else if (ack.isRedeliveredAck()) {
298            // No processing for redelivered needed
299            return;
300        } else {
301            throw new JMSException("Invalid acknowledgment: " + ack);
302        }
303
304        dispatchMatched();
305    }
306
307    private void updateStatsOnAck(final ConnectionContext context, final MessageAck ack) {
308        if (context.isInTransaction()) {
309            context.getTransaction().addSynchronization(new Synchronization() {
310
311                @Override
312                public void afterRollback() {
313                    contractPrefetchExtension(ack.getMessageCount());
314                }
315
316                @Override
317                public void afterCommit() throws Exception {
318                    contractPrefetchExtension(ack.getMessageCount());
319                    updateStatsOnAck(ack);
320                    dispatchMatched();
321                }
322            });
323        } else {
324            updateStatsOnAck(ack);
325        }
326    }
327
328    @Override
329    public Response pullMessage(ConnectionContext context, final MessagePull pull) throws Exception {
330
331        // The slave should not deliver pull messages.
332        if (getPrefetchSize() == 0) {
333
334            final long currentDispatchedCount = getSubscriptionStatistics().getDispatched().getCount();
335            prefetchExtension.set(pull.getQuantity());
336            dispatchMatched();
337
338            // If there was nothing dispatched.. we may need to setup a timeout.
339            if (currentDispatchedCount == getSubscriptionStatistics().getDispatched().getCount() || pull.isAlwaysSignalDone()) {
340
341                // immediate timeout used by receiveNoWait()
342                if (pull.getTimeout() == -1) {
343                    // Send a NULL message to signal nothing pending.
344                    dispatch(null);
345                    prefetchExtension.set(0);
346                }
347
348                if (pull.getTimeout() > 0) {
349                    scheduler.executeAfterDelay(new Runnable() {
350
351                        @Override
352                        public void run() {
353                            pullTimeout(currentDispatchedCount, pull.isAlwaysSignalDone());
354                        }
355                    }, pull.getTimeout());
356                }
357            }
358        }
359        return null;
360    }
361
362    /**
363     * Occurs when a pull times out. If nothing has been dispatched since the
364     * timeout was setup, then send the NULL message.
365     */
366    private final void pullTimeout(long currentDispatchedCount, boolean alwaysSendDone) {
367        synchronized (matchedListMutex) {
368            if (currentDispatchedCount == getSubscriptionStatistics().getDispatched().getCount() || alwaysSendDone) {
369                try {
370                    dispatch(null);
371                } catch (Exception e) {
372                    context.getConnection().serviceException(e);
373                } finally {
374                    prefetchExtension.set(0);
375                }
376            }
377        }
378    }
379
380    /**
381     * Update the statistics on message ack.
382     * @param ack
383     */
384    private void updateStatsOnAck(final MessageAck ack) {
385        synchronized(dispatchLock) {
386            boolean inAckRange = false;
387            List<MessageReference> removeList = new ArrayList<MessageReference>();
388            for (final MessageReference node : dispatched) {
389                MessageId messageId = node.getMessageId();
390                if (ack.getFirstMessageId() == null
391                        || ack.getFirstMessageId().equals(messageId)) {
392                    inAckRange = true;
393                }
394                if (inAckRange) {
395                    removeList.add(node);
396                    if (ack.getLastMessageId().equals(messageId)) {
397                        break;
398                    }
399                }
400            }
401
402            for (final MessageReference node : removeList) {
403                dispatched.remove(node);
404                getSubscriptionStatistics().getInflightMessageSize().addSize(-node.getSize());
405                getSubscriptionStatistics().getDequeues().increment();
406                ((Destination)node.getRegionDestination()).getDestinationStatistics().getDequeues().increment();
407                ((Destination)node.getRegionDestination()).getDestinationStatistics().getInflight().decrement();
408                if (info.isNetworkSubscription()) {
409                    ((Destination)node.getRegionDestination()).getDestinationStatistics().getForwards().add(ack.getMessageCount());
410                }
411                if (ack.isExpiredAck()) {
412                    destination.getDestinationStatistics().getExpired().add(ack.getMessageCount());
413                }
414                if (!ack.isInTransaction()) {
415                    contractPrefetchExtension(1);
416                }
417            }
418        }
419    }
420
421    @Override
422    public int getPendingQueueSize() {
423        return matched();
424    }
425
426    @Override
427    public int getDispatchedQueueSize() {
428        return (int)(getSubscriptionStatistics().getDispatched().getCount() -
429                     getSubscriptionStatistics().getDequeues().getCount());
430    }
431
432    public int getMaximumPendingMessages() {
433        return maximumPendingMessages;
434    }
435
436    @Override
437    public long getDispatchedCounter() {
438        return getSubscriptionStatistics().getDispatched().getCount();
439    }
440
441    @Override
442    public long getEnqueueCounter() {
443        return getSubscriptionStatistics().getEnqueues().getCount();
444    }
445
446    @Override
447    public long getDequeueCounter() {
448        return getSubscriptionStatistics().getDequeues().getCount();
449    }
450
451    /**
452     * @return the number of messages discarded due to being a slow consumer
453     */
454    public int discarded() {
455        synchronized (matchedListMutex) {
456            return discarded;
457        }
458    }
459
460    /**
461     * @return the number of matched messages (messages targeted for the
462     *         subscription but not yet able to be dispatched due to the
463     *         prefetch buffer being full).
464     */
465    public int matched() {
466        synchronized (matchedListMutex) {
467            return matched.size();
468        }
469    }
470
471    /**
472     * Sets the maximum number of pending messages that can be matched against
473     * this consumer before old messages are discarded.
474     */
475    public void setMaximumPendingMessages(int maximumPendingMessages) {
476        this.maximumPendingMessages = maximumPendingMessages;
477    }
478
479    public MessageEvictionStrategy getMessageEvictionStrategy() {
480        return messageEvictionStrategy;
481    }
482
483    /**
484     * Sets the eviction strategy used to decide which message to evict when the
485     * slow consumer needs to discard messages
486     */
487    public void setMessageEvictionStrategy(MessageEvictionStrategy messageEvictionStrategy) {
488        this.messageEvictionStrategy = messageEvictionStrategy;
489    }
490
491    public int getMaxProducersToAudit() {
492        return maxProducersToAudit;
493    }
494
495    public synchronized void setMaxProducersToAudit(int maxProducersToAudit) {
496        this.maxProducersToAudit = maxProducersToAudit;
497        if (audit != null) {
498            audit.setMaximumNumberOfProducersToTrack(maxProducersToAudit);
499        }
500    }
501
502    public int getMaxAuditDepth() {
503        return maxAuditDepth;
504    }
505
506    public synchronized void setMaxAuditDepth(int maxAuditDepth) {
507        this.maxAuditDepth = maxAuditDepth;
508        if (audit != null) {
509            audit.setAuditDepth(maxAuditDepth);
510        }
511    }
512
513    public boolean isEnableAudit() {
514        return enableAudit;
515    }
516
517    public synchronized void setEnableAudit(boolean enableAudit) {
518        this.enableAudit = enableAudit;
519        if (enableAudit && audit == null) {
520            audit = new ActiveMQMessageAudit(maxAuditDepth,maxProducersToAudit);
521        }
522    }
523
524    // Implementation methods
525    // -------------------------------------------------------------------------
526    @Override
527    public boolean isFull() {
528        return getPrefetchSize() == 0 ? prefetchExtension.get() == 0 : getDispatchedQueueSize() - prefetchExtension.get() >= info.getPrefetchSize();
529    }
530
531    @Override
532    public int getInFlightSize() {
533        return getDispatchedQueueSize();
534    }
535
536    /**
537     * @return true when 60% or more room is left for dispatching messages
538     */
539    @Override
540    public boolean isLowWaterMark() {
541        return (getDispatchedQueueSize() - prefetchExtension.get()) <= (info.getPrefetchSize() * .4);
542    }
543
544    /**
545     * @return true when 10% or less room is left for dispatching messages
546     */
547    @Override
548    public boolean isHighWaterMark() {
549        return (getDispatchedQueueSize() - prefetchExtension.get()) >= (info.getPrefetchSize() * .9);
550    }
551
552    /**
553     * @param memoryUsageHighWaterMark the memoryUsageHighWaterMark to set
554     */
555    public void setMemoryUsageHighWaterMark(int memoryUsageHighWaterMark) {
556        this.memoryUsageHighWaterMark = memoryUsageHighWaterMark;
557    }
558
559    /**
560     * @return the memoryUsageHighWaterMark
561     */
562    public int getMemoryUsageHighWaterMark() {
563        return this.memoryUsageHighWaterMark;
564    }
565
566    /**
567     * @return the usageManager
568     */
569    public SystemUsage getUsageManager() {
570        return this.usageManager;
571    }
572
573    /**
574     * @return the matched
575     */
576    public PendingMessageCursor getMatched() {
577        return this.matched;
578    }
579
580    /**
581     * @param matched the matched to set
582     */
583    public void setMatched(PendingMessageCursor matched) {
584        this.matched = matched;
585    }
586
587    /**
588     * inform the MessageConsumer on the client to change it's prefetch
589     *
590     * @param newPrefetch
591     */
592    @Override
593    public void updateConsumerPrefetch(int newPrefetch) {
594        if (context != null && context.getConnection() != null && context.getConnection().isManageable()) {
595            ConsumerControl cc = new ConsumerControl();
596            cc.setConsumerId(info.getConsumerId());
597            cc.setPrefetch(newPrefetch);
598            context.getConnection().dispatchAsync(cc);
599        }
600    }
601
602    private void dispatchMatched() throws IOException {
603        synchronized (matchedListMutex) {
604            if (!matched.isEmpty() && !isFull()) {
605                try {
606                    matched.reset();
607
608                    while (matched.hasNext() && !isFull()) {
609                        MessageReference message = matched.next();
610                        message.decrementReferenceCount();
611                        matched.remove();
612                        // Message may have been sitting in the matched list a while
613                        // waiting for the consumer to ak the message.
614                        if (message.isExpired()) {
615                            discard(message);
616                            continue; // just drop it.
617                        }
618                        dispatch(message);
619                    }
620                } finally {
621                    matched.release();
622                }
623            }
624        }
625    }
626
627    private void dispatch(final MessageReference node) throws IOException {
628        Message message = node != null ? node.getMessage() : null;
629        if (node != null) {
630            node.incrementReferenceCount();
631        }
632        // Make sure we can dispatch a message.
633        MessageDispatch md = new MessageDispatch();
634        md.setMessage(message);
635        md.setConsumerId(info.getConsumerId());
636        if (node != null) {
637            md.setDestination(((Destination)node.getRegionDestination()).getActiveMQDestination());
638            synchronized(dispatchLock) {
639                getSubscriptionStatistics().getDispatched().increment();
640                dispatched.add(node);
641                getSubscriptionStatistics().getInflightMessageSize().addSize(node.getSize());
642            }
643
644            // Keep track if this subscription is receiving messages from a single destination.
645            if (singleDestination) {
646                if (destination == null) {
647                    destination = (Destination)node.getRegionDestination();
648                } else {
649                    if (destination != node.getRegionDestination()) {
650                        singleDestination = false;
651                    }
652                }
653            }
654
655            if (getPrefetchSize() == 0) {
656                decrementPrefetchExtension(1);
657            }
658        }
659
660        if (info.isDispatchAsync()) {
661            if (node != null) {
662                md.setTransmitCallback(new TransmitCallback() {
663
664                    @Override
665                    public void onSuccess() {
666                        Destination regionDestination = (Destination) node.getRegionDestination();
667                        regionDestination.getDestinationStatistics().getDispatched().increment();
668                        regionDestination.getDestinationStatistics().getInflight().increment();
669                        node.decrementReferenceCount();
670                    }
671
672                    @Override
673                    public void onFailure() {
674                        Destination regionDestination = (Destination) node.getRegionDestination();
675                        regionDestination.getDestinationStatistics().getDispatched().increment();
676                        regionDestination.getDestinationStatistics().getInflight().increment();
677                        node.decrementReferenceCount();
678                    }
679                });
680            }
681            context.getConnection().dispatchAsync(md);
682        } else {
683            context.getConnection().dispatchSync(md);
684            if (node != null) {
685                Destination regionDestination = (Destination) node.getRegionDestination();
686                regionDestination.getDestinationStatistics().getDispatched().increment();
687                regionDestination.getDestinationStatistics().getInflight().increment();
688                node.decrementReferenceCount();
689            }
690        }
691    }
692
693    private void discard(MessageReference message) {
694        discarding = true;
695        try {
696            message.decrementReferenceCount();
697            matched.remove(message);
698            discarded++;
699            if (destination != null) {
700                destination.getDestinationStatistics().getDequeues().increment();
701            }
702            LOG.debug("{}, discarding message {}", this, message);
703            Destination dest = (Destination) message.getRegionDestination();
704            if (dest != null) {
705                dest.messageDiscarded(getContext(), this, message);
706            }
707            broker.getRoot().sendToDeadLetterQueue(getContext(), message, this, new Throwable("TopicSubDiscard. ID:" + info.getConsumerId()));
708        } finally {
709            discarding = false;
710        }
711    }
712
713    @Override
714    public String toString() {
715        return "TopicSubscription:" + " consumer=" + info.getConsumerId() + ", destinations=" + destinations.size() + ", dispatched=" + getDispatchedQueueSize() + ", delivered="
716                + getDequeueCounter() + ", matched=" + matched() + ", discarded=" + discarded() + ", prefetchExtension=" + prefetchExtension.get()
717                + ", usePrefetchExtension=" + isUsePrefetchExtension();
718    }
719
720    @Override
721    public void destroy() {
722        this.active=false;
723        synchronized (matchedListMutex) {
724            try {
725                matched.destroy();
726            } catch (Exception e) {
727                LOG.warn("Failed to destroy cursor", e);
728            }
729        }
730        setSlowConsumer(false);
731        synchronized(dispatchLock) {
732            dispatched.clear();
733        }
734    }
735
736    @Override
737    public int getPrefetchSize() {
738        return info.getPrefetchSize();
739    }
740
741    @Override
742    public void setPrefetchSize(int newSize) {
743        info.setPrefetchSize(newSize);
744        try {
745            dispatchMatched();
746        } catch(Exception e) {
747            LOG.trace("Caught exception on dispatch after prefetch size change.");
748        }
749    }
750
751}