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                    node.decrementReferenceCount();
236                    if (broker.isExpired(node)) {
237                        ((Destination) node.getRegionDestination()).getDestinationStatistics().getExpired().increment();
238                        broker.messageExpired(getContext(), node, this);
239                    }
240                    break;
241                }
242            }
243        } finally {
244            matched.release();
245        }
246    }
247
248    @Override
249    public void processMessageDispatchNotification(MessageDispatchNotification mdn) {
250        synchronized (matchedListMutex) {
251            try {
252                matched.reset();
253                while (matched.hasNext()) {
254                    MessageReference node = matched.next();
255                    node.decrementReferenceCount();
256                    if (node.getMessageId().equals(mdn.getMessageId())) {
257                        synchronized(dispatchLock) {
258                            matched.remove();
259                            getSubscriptionStatistics().getDispatched().increment();
260                            dispatched.add(node);
261                            getSubscriptionStatistics().getInflightMessageSize().addSize(node.getSize());
262                            node.decrementReferenceCount();
263                        }
264                        break;
265                    }
266                }
267            } finally {
268                matched.release();
269            }
270        }
271    }
272
273    @Override
274    public synchronized void acknowledge(final ConnectionContext context, final MessageAck ack) throws Exception {
275        super.acknowledge(context, ack);
276
277        if (ack.isStandardAck()) {
278            updateStatsOnAck(context, ack);
279        } else if (ack.isPoisonAck()) {
280            if (ack.isInTransaction()) {
281                throw new JMSException("Poison ack cannot be transacted: " + ack);
282            }
283            updateStatsOnAck(context, ack);
284            contractPrefetchExtension(ack.getMessageCount());
285        } else if (ack.isIndividualAck()) {
286            updateStatsOnAck(context, ack);
287            if (ack.isInTransaction()) {
288                expandPrefetchExtension(1);
289            }
290        } else if (ack.isExpiredAck()) {
291            updateStatsOnAck(ack);
292            contractPrefetchExtension(ack.getMessageCount());
293        } else if (ack.isDeliveredAck()) {
294            // Message was delivered but not acknowledged: update pre-fetch counters.
295           expandPrefetchExtension(ack.getMessageCount());
296        } else if (ack.isRedeliveredAck()) {
297            // No processing for redelivered needed
298            return;
299        } else {
300            throw new JMSException("Invalid acknowledgment: " + ack);
301        }
302
303        dispatchMatched();
304    }
305
306    private void updateStatsOnAck(final ConnectionContext context, final MessageAck ack) {
307        if (context.isInTransaction()) {
308            context.getTransaction().addSynchronization(new Synchronization() {
309
310                @Override
311                public void afterRollback() {
312                    contractPrefetchExtension(ack.getMessageCount());
313                }
314
315                @Override
316                public void afterCommit() throws Exception {
317                    contractPrefetchExtension(ack.getMessageCount());
318                    updateStatsOnAck(ack);
319                    dispatchMatched();
320                }
321            });
322        } else {
323            updateStatsOnAck(ack);
324        }
325    }
326
327    @Override
328    public Response pullMessage(ConnectionContext context, final MessagePull pull) throws Exception {
329
330        // The slave should not deliver pull messages.
331        if (getPrefetchSize() == 0) {
332
333            final long currentDispatchedCount = getSubscriptionStatistics().getDispatched().getCount();
334            prefetchExtension.set(pull.getQuantity());
335            dispatchMatched();
336
337            // If there was nothing dispatched.. we may need to setup a timeout.
338            if (currentDispatchedCount == getSubscriptionStatistics().getDispatched().getCount() || pull.isAlwaysSignalDone()) {
339
340                // immediate timeout used by receiveNoWait()
341                if (pull.getTimeout() == -1) {
342                    // Send a NULL message to signal nothing pending.
343                    dispatch(null);
344                    prefetchExtension.set(0);
345                }
346
347                if (pull.getTimeout() > 0) {
348                    scheduler.executeAfterDelay(new Runnable() {
349
350                        @Override
351                        public void run() {
352                            pullTimeout(currentDispatchedCount, pull.isAlwaysSignalDone());
353                        }
354                    }, pull.getTimeout());
355                }
356            }
357        }
358        return null;
359    }
360
361    /**
362     * Occurs when a pull times out. If nothing has been dispatched since the
363     * timeout was setup, then send the NULL message.
364     */
365    private final void pullTimeout(long currentDispatchedCount, boolean alwaysSendDone) {
366        synchronized (matchedListMutex) {
367            if (currentDispatchedCount == getSubscriptionStatistics().getDispatched().getCount() || alwaysSendDone) {
368                try {
369                    dispatch(null);
370                } catch (Exception e) {
371                    context.getConnection().serviceException(e);
372                } finally {
373                    prefetchExtension.set(0);
374                }
375            }
376        }
377    }
378
379    /**
380     * Update the statistics on message ack.
381     * @param ack
382     */
383    private void updateStatsOnAck(final MessageAck ack) {
384        synchronized(dispatchLock) {
385            boolean inAckRange = false;
386            List<MessageReference> removeList = new ArrayList<MessageReference>();
387            for (final MessageReference node : dispatched) {
388                MessageId messageId = node.getMessageId();
389                if (ack.getFirstMessageId() == null
390                        || ack.getFirstMessageId().equals(messageId)) {
391                    inAckRange = true;
392                }
393                if (inAckRange) {
394                    removeList.add(node);
395                    if (ack.getLastMessageId().equals(messageId)) {
396                        break;
397                    }
398                }
399            }
400
401            for (final MessageReference node : removeList) {
402                dispatched.remove(node);
403                getSubscriptionStatistics().getInflightMessageSize().addSize(-node.getSize());
404                getSubscriptionStatistics().getDequeues().increment();
405                ((Destination)node.getRegionDestination()).getDestinationStatistics().getDequeues().increment();
406                ((Destination)node.getRegionDestination()).getDestinationStatistics().getInflight().decrement();
407                if (info.isNetworkSubscription()) {
408                    ((Destination)node.getRegionDestination()).getDestinationStatistics().getForwards().add(ack.getMessageCount());
409                }
410                if (ack.isExpiredAck()) {
411                    destination.getDestinationStatistics().getExpired().add(ack.getMessageCount());
412                }
413                if (!ack.isInTransaction()) {
414                    contractPrefetchExtension(1);
415                }
416            }
417        }
418    }
419
420    @Override
421    public int countBeforeFull() {
422        return getPrefetchSize() == 0 ? prefetchExtension.get() : info.getPrefetchSize() + prefetchExtension.get() - getDispatchedQueueSize();
423    }
424
425    @Override
426    public int getPendingQueueSize() {
427        return matched();
428    }
429
430    @Override
431    public long getPendingMessageSize() {
432        synchronized (matchedListMutex) {
433            return matched.messageSize();
434        }
435    }
436
437    @Override
438    public int getDispatchedQueueSize() {
439        return (int)(getSubscriptionStatistics().getDispatched().getCount() -
440                     getSubscriptionStatistics().getDequeues().getCount());
441    }
442
443    public int getMaximumPendingMessages() {
444        return maximumPendingMessages;
445    }
446
447    @Override
448    public long getDispatchedCounter() {
449        return getSubscriptionStatistics().getDispatched().getCount();
450    }
451
452    @Override
453    public long getEnqueueCounter() {
454        return getSubscriptionStatistics().getEnqueues().getCount();
455    }
456
457    @Override
458    public long getDequeueCounter() {
459        return getSubscriptionStatistics().getDequeues().getCount();
460    }
461
462    /**
463     * @return the number of messages discarded due to being a slow consumer
464     */
465    public int discarded() {
466        synchronized (matchedListMutex) {
467            return discarded;
468        }
469    }
470
471    /**
472     * @return the number of matched messages (messages targeted for the
473     *         subscription but not yet able to be dispatched due to the
474     *         prefetch buffer being full).
475     */
476    public int matched() {
477        synchronized (matchedListMutex) {
478            return matched.size();
479        }
480    }
481
482    /**
483     * Sets the maximum number of pending messages that can be matched against
484     * this consumer before old messages are discarded.
485     */
486    public void setMaximumPendingMessages(int maximumPendingMessages) {
487        this.maximumPendingMessages = maximumPendingMessages;
488    }
489
490    public MessageEvictionStrategy getMessageEvictionStrategy() {
491        return messageEvictionStrategy;
492    }
493
494    /**
495     * Sets the eviction strategy used to decide which message to evict when the
496     * slow consumer needs to discard messages
497     */
498    public void setMessageEvictionStrategy(MessageEvictionStrategy messageEvictionStrategy) {
499        this.messageEvictionStrategy = messageEvictionStrategy;
500    }
501
502    public int getMaxProducersToAudit() {
503        return maxProducersToAudit;
504    }
505
506    public synchronized void setMaxProducersToAudit(int maxProducersToAudit) {
507        this.maxProducersToAudit = maxProducersToAudit;
508        if (audit != null) {
509            audit.setMaximumNumberOfProducersToTrack(maxProducersToAudit);
510        }
511    }
512
513    public int getMaxAuditDepth() {
514        return maxAuditDepth;
515    }
516
517    public synchronized void setMaxAuditDepth(int maxAuditDepth) {
518        this.maxAuditDepth = maxAuditDepth;
519        if (audit != null) {
520            audit.setAuditDepth(maxAuditDepth);
521        }
522    }
523
524    public boolean isEnableAudit() {
525        return enableAudit;
526    }
527
528    public synchronized void setEnableAudit(boolean enableAudit) {
529        this.enableAudit = enableAudit;
530        if (enableAudit && audit == null) {
531            audit = new ActiveMQMessageAudit(maxAuditDepth,maxProducersToAudit);
532        }
533    }
534
535    // Implementation methods
536    // -------------------------------------------------------------------------
537    @Override
538    public boolean isFull() {
539        return getPrefetchSize() == 0 ? prefetchExtension.get() == 0 : getDispatchedQueueSize() - prefetchExtension.get() >= info.getPrefetchSize();
540    }
541
542    @Override
543    public int getInFlightSize() {
544        return getDispatchedQueueSize();
545    }
546
547    /**
548     * @return true when 60% or more room is left for dispatching messages
549     */
550    @Override
551    public boolean isLowWaterMark() {
552        return (getDispatchedQueueSize() - prefetchExtension.get()) <= (info.getPrefetchSize() * .4);
553    }
554
555    /**
556     * @return true when 10% or less room is left for dispatching messages
557     */
558    @Override
559    public boolean isHighWaterMark() {
560        return (getDispatchedQueueSize() - prefetchExtension.get()) >= (info.getPrefetchSize() * .9);
561    }
562
563    /**
564     * @param memoryUsageHighWaterMark the memoryUsageHighWaterMark to set
565     */
566    public void setMemoryUsageHighWaterMark(int memoryUsageHighWaterMark) {
567        this.memoryUsageHighWaterMark = memoryUsageHighWaterMark;
568    }
569
570    /**
571     * @return the memoryUsageHighWaterMark
572     */
573    public int getMemoryUsageHighWaterMark() {
574        return this.memoryUsageHighWaterMark;
575    }
576
577    /**
578     * @return the usageManager
579     */
580    public SystemUsage getUsageManager() {
581        return this.usageManager;
582    }
583
584    /**
585     * @return the matched
586     */
587    public PendingMessageCursor getMatched() {
588        return this.matched;
589    }
590
591    /**
592     * @param matched the matched to set
593     */
594    public void setMatched(PendingMessageCursor matched) {
595        this.matched = matched;
596    }
597
598    /**
599     * inform the MessageConsumer on the client to change it's prefetch
600     *
601     * @param newPrefetch
602     */
603    @Override
604    public void updateConsumerPrefetch(int newPrefetch) {
605        if (context != null && context.getConnection() != null && context.getConnection().isManageable()) {
606            ConsumerControl cc = new ConsumerControl();
607            cc.setConsumerId(info.getConsumerId());
608            cc.setPrefetch(newPrefetch);
609            context.getConnection().dispatchAsync(cc);
610        }
611    }
612
613    private void dispatchMatched() throws IOException {
614        synchronized (matchedListMutex) {
615            if (!matched.isEmpty() && !isFull()) {
616                try {
617                    matched.reset();
618
619                    while (matched.hasNext() && !isFull()) {
620                        MessageReference message = matched.next();
621                        message.decrementReferenceCount();
622                        matched.remove();
623                        // Message may have been sitting in the matched list a while
624                        // waiting for the consumer to ak the message.
625                        if (message.isExpired()) {
626                            discard(message);
627                            continue; // just drop it.
628                        }
629                        dispatch(message);
630                    }
631                } finally {
632                    matched.release();
633                }
634            }
635        }
636    }
637
638    private void dispatch(final MessageReference node) throws IOException {
639        Message message = node != null ? node.getMessage() : null;
640        if (node != null) {
641            node.incrementReferenceCount();
642        }
643        // Make sure we can dispatch a message.
644        MessageDispatch md = new MessageDispatch();
645        md.setMessage(message);
646        md.setConsumerId(info.getConsumerId());
647        if (node != null) {
648            md.setDestination(((Destination)node.getRegionDestination()).getActiveMQDestination());
649            synchronized(dispatchLock) {
650                getSubscriptionStatistics().getDispatched().increment();
651                dispatched.add(node);
652                getSubscriptionStatistics().getInflightMessageSize().addSize(node.getSize());
653            }
654
655            // Keep track if this subscription is receiving messages from a single destination.
656            if (singleDestination) {
657                if (destination == null) {
658                    destination = (Destination)node.getRegionDestination();
659                } else {
660                    if (destination != node.getRegionDestination()) {
661                        singleDestination = false;
662                    }
663                }
664            }
665
666            if (getPrefetchSize() == 0) {
667                decrementPrefetchExtension(1);
668            }
669        }
670
671        if (info.isDispatchAsync()) {
672            if (node != null) {
673                md.setTransmitCallback(new TransmitCallback() {
674
675                    @Override
676                    public void onSuccess() {
677                        Destination regionDestination = (Destination) node.getRegionDestination();
678                        regionDestination.getDestinationStatistics().getDispatched().increment();
679                        regionDestination.getDestinationStatistics().getInflight().increment();
680                        node.decrementReferenceCount();
681                    }
682
683                    @Override
684                    public void onFailure() {
685                        Destination regionDestination = (Destination) node.getRegionDestination();
686                        regionDestination.getDestinationStatistics().getDispatched().increment();
687                        regionDestination.getDestinationStatistics().getInflight().increment();
688                        node.decrementReferenceCount();
689                    }
690                });
691            }
692            context.getConnection().dispatchAsync(md);
693        } else {
694            context.getConnection().dispatchSync(md);
695            if (node != null) {
696                Destination regionDestination = (Destination) node.getRegionDestination();
697                regionDestination.getDestinationStatistics().getDispatched().increment();
698                regionDestination.getDestinationStatistics().getInflight().increment();
699                node.decrementReferenceCount();
700            }
701        }
702    }
703
704    private void discard(MessageReference message) {
705        discarding = true;
706        try {
707            message.decrementReferenceCount();
708            matched.remove(message);
709            discarded++;
710            if (destination != null) {
711                destination.getDestinationStatistics().getDequeues().increment();
712            }
713            LOG.debug("{}, discarding message {}", this, message);
714            Destination dest = (Destination) message.getRegionDestination();
715            if (dest != null) {
716                dest.messageDiscarded(getContext(), this, message);
717            }
718            broker.getRoot().sendToDeadLetterQueue(getContext(), message, this, new Throwable("TopicSubDiscard. ID:" + info.getConsumerId()));
719        } finally {
720            discarding = false;
721        }
722    }
723
724    @Override
725    public String toString() {
726        return "TopicSubscription:" + " consumer=" + info.getConsumerId() + ", destinations=" + destinations.size() + ", dispatched=" + getDispatchedQueueSize() + ", delivered="
727                + getDequeueCounter() + ", matched=" + matched() + ", discarded=" + discarded() + ", prefetchExtension=" + prefetchExtension.get()
728                + ", usePrefetchExtension=" + isUsePrefetchExtension();
729    }
730
731    @Override
732    public void destroy() {
733        this.active=false;
734        synchronized (matchedListMutex) {
735            try {
736                matched.destroy();
737            } catch (Exception e) {
738                LOG.warn("Failed to destroy cursor", e);
739            }
740        }
741        setSlowConsumer(false);
742        synchronized(dispatchLock) {
743            dispatched.clear();
744        }
745    }
746
747    @Override
748    public int getPrefetchSize() {
749        return info.getPrefetchSize();
750    }
751
752    @Override
753    public void setPrefetchSize(int newSize) {
754        info.setPrefetchSize(newSize);
755        try {
756            dispatchMatched();
757        } catch(Exception e) {
758            LOG.trace("Caught exception on dispatch after prefetch size change.");
759        }
760    }
761
762}