https://issues.apache.org/jira/browse/AMQ-6264

Fire advisory for slow consumer outside the pending lock.

activemq-broker/src/main/java/org/apache/activemq/broker/region/PrefetchSubscription.java

@@ -678,6 +678,8 @@ public abstract class PrefetchSubscription extends AbstractSubscription {
 
     // made public so it can be used in MQTTProtocolConverter
     public void dispatchPending() throws IOException {
+        List<Destination> slowConsumerTargets = null;
+
         synchronized(pendingLock) {
             try {
                 int numberToDispatch = countBeforeFull();
@@ -721,14 +723,18 @@ public abstract class PrefetchSubscription extends AbstractSubscription {
                     }
                 } else if (!isSlowConsumer()) {
                     setSlowConsumer(true);
-                    for (Destination dest :destinations) {
-                        dest.slowConsumer(context, this);
-                    }
+                    slowConsumerTargets = destinations;
                 }
             } finally {
                 pending.release();
             }
         }
+
+        if (slowConsumerTargets != null) {
+            for (Destination dest : slowConsumerTargets) {
+                dest.slowConsumer(context, this);
+            }
+        }
     }
 
     protected void setPendingBatchSize(PendingMessageCursor pending, int numberToDispatch) {

activemq-unit-tests/src/test/java/org/apache/activemq/bugs/AMQ6264Test.java

@@ -0,0 +1,135 @@
+/*
+ * 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.bugs;
+
+import static org.junit.Assert.assertNotNull;
+
+import java.util.UUID;
+
+import javax.jms.BytesMessage;
+import javax.jms.Connection;
+import javax.jms.Message;
+import javax.jms.MessageConsumer;
+import javax.jms.MessageProducer;
+import javax.jms.Session;
+import javax.jms.Topic;
+
+import org.apache.activemq.ActiveMQConnectionFactory;
+import org.apache.activemq.advisory.AdvisorySupport;
+import org.apache.activemq.broker.BrokerService;
+import org.apache.activemq.broker.region.policy.PolicyEntry;
+import org.apache.activemq.broker.region.policy.PolicyMap;
+import org.apache.activemq.command.ActiveMQDestination;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TestName;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class AMQ6264Test {
+
+    private static final Logger LOG = LoggerFactory.getLogger(AMQ6264Test.class);
+
+    @Rule
+    public final TestName testName = new TestName();
+
+    protected final int MESSAGE_COUNT = 2000;
+
+    private final String topicPrefix = "topic.";
+    private final String topicFilter = topicPrefix + ">";
+    private final String topicA = "topic.A";
+
+    private BrokerService broker;
+    private Connection connection;
+    private String connectionURI;
+
+    @Test(timeout = 60000)
+    public void testSlowConsumerAdvisory() throws Exception {
+        Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
+        Topic topic = session.createTopic(topicFilter);
+        MessageConsumer consumer = session.createDurableSubscriber(topic, testName.getMethodName());
+        assertNotNull(consumer);
+
+        Topic advisoryTopic = AdvisorySupport.getSlowConsumerAdvisoryTopic(
+            ActiveMQDestination.createDestination(topicA, ActiveMQDestination.TOPIC_TYPE));
+        session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
+        MessageConsumer advisoryConsumer = session.createConsumer(advisoryTopic);
+
+        // start throwing messages at the consumer one for an ongoing series of
+        // matching topics for the subscription's filter.
+        MessageProducer producer = session.createProducer(null);
+
+        // Send one to the destination where we want a matching advisory
+        producer.send(session.createTopic(topicA), session.createMessage());
+
+        for (int i = 0; i < MESSAGE_COUNT; i++) {
+            BytesMessage m = session.createBytesMessage();
+            m.writeBytes(new byte[1024]);
+            Topic newTopic = session.createTopic(topicPrefix + UUID.randomUUID().toString());
+            LOG.debug("Sending message to next topic: {}", newTopic);
+            producer.send(newTopic, m);
+        }
+
+        Message msg = advisoryConsumer.receive(1000);
+        assertNotNull(msg);
+    }
+
+    @Before
+    public void setUp() throws Exception {
+        broker = createBroker();
+
+        connectionURI = broker.getTransportConnectors().get(0).getPublishableConnectString();
+
+        ActiveMQConnectionFactory factory = createConnectionFactory();
+        connection = factory.createConnection();
+        connection.setClientID(getClass().getSimpleName());
+        connection.start();
+    }
+
+    @After
+    public void tearDown() throws Exception {
+        connection.close();
+        if (broker != null) {
+            broker.stop();
+        }
+    }
+
+    protected ActiveMQConnectionFactory createConnectionFactory() throws Exception {
+        return new ActiveMQConnectionFactory(connectionURI);
+    }
+
+    protected BrokerService createBroker() throws Exception {
+        BrokerService answer = new BrokerService();
+
+        answer.setPersistent(false);
+        PolicyEntry policy = new PolicyEntry();
+        policy.setAdvisoryForSlowConsumers(true);
+        policy.setProducerFlowControl(false);
+        PolicyMap pMap = new PolicyMap();
+        pMap.setDefaultEntry(policy);
+
+        answer.setUseJmx(true);
+        answer.setDestinationPolicy(pMap);
+        answer.addConnector("tcp://0.0.0.0:0");
+        answer.setDeleteAllMessagesOnStartup(true);
+        answer.start();
+
+        return answer;
+    }
+}