AMQ-7193 - resolve intermittent NPE on duplex network connector start…

…; wait for start completion before dispatching inbound messages, fix and test

activemq-broker/src/main/java/org/apache/activemq/network/DemandForwardingBridgeSupport.java

@@ -808,6 +808,7 @@ public void run() {
                                 if (!isPermissableDestination(message.getDestination(), true)) {
                                     return;
                                 }
+                                safeWaitUntilStarted();
                                 // message being forwarded - we need to
                                 // propagate the response to our local send
                                 if (canDuplexDispatch(message)) {

activemq-unit-tests/src/test/java/org/apache/activemq/network/DuplexStartNpeTest.java

@@ -0,0 +1,155 @@
+/**
+ * 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
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * 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.network;
+
+import org.apache.activemq.ActiveMQConnectionFactory;
+import org.apache.activemq.broker.BrokerPlugin;
+import org.apache.activemq.broker.BrokerPluginSupport;
+import org.apache.activemq.broker.BrokerService;
+import org.apache.activemq.broker.ConnectionContext;
+import org.apache.activemq.command.ActiveMQDestination;
+import org.apache.activemq.command.ActiveMQQueue;
+import org.apache.activemq.command.ActiveMQTextMessage;
+import org.apache.activemq.command.ConnectionInfo;
+import org.apache.activemq.util.TestUtils;
+import org.junit.After;
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.jms.Connection;
+import javax.jms.JMSException;
+import javax.jms.MessageConsumer;
+import javax.jms.MessageProducer;
+import javax.jms.Session;
+import java.net.URI;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+
+import static junit.framework.TestCase.assertNotNull;
+
+public class DuplexStartNpeTest {
+    private static final Logger LOG = LoggerFactory.getLogger(DuplexStartNpeTest.class);
+    final ActiveMQQueue dest = new ActiveMQQueue("QQ");
+    final List<BrokerService> brokerServices = new ArrayList<>();
+    final List<Connection> connections = new ArrayList();
+    final static String urlString = "tcp://localhost:" + TestUtils.findOpenPort();
+    final static int NUM_MESSAGES = 10;
+
+    @Test
+    public void reproduceNpe() throws Exception {
+        BrokerService broker0 = createBroker();
+
+        NetworkConnector networkConnector = broker0.addNetworkConnector("masterslave:(" + urlString + "," + urlString + ")");
+        networkConnector.setDuplex(true);
+        networkConnector.setStaticBridge(true);
+
+        // ensure there is demand on start
+        networkConnector.setStaticallyIncludedDestinations(Arrays.<ActiveMQDestination>asList(new ActiveMQQueue[]{dest}));
+
+
+        broker0.start();
+
+        publish(broker0.getVmConnectorURI());
+
+
+        BrokerService broker1 = createBroker();
+        broker1.addConnector(urlString);
+
+        broker1.setPlugins(new BrokerPlugin[] {
+                new BrokerPluginSupport() {
+                    @Override
+                    public void addConnection(ConnectionContext context, ConnectionInfo info) throws Exception {
+                        super.addConnection(context, info);
+
+                        if (info.getClientId() != null  && info.getClientId().contains("_duplex_")) {
+                            LOG.info("New connection for broker1: " + info);
+                            // snooz on return to simulate stall
+                            TimeUnit.MILLISECONDS.sleep(500);
+                        }
+                    }
+                }
+        });
+
+        broker1.start();
+
+        // get the message over the bridge
+        consume(new URI(urlString));
+    }
+
+    private void consume(URI uri) throws Exception {
+        MessageConsumer messageConsumer = connectionFactory(uri).createConnection().createSession(false, Session.AUTO_ACKNOWLEDGE).createConsumer(dest);
+        for (int i=0; i<NUM_MESSAGES; i++) {
+            assertNotNull("got message: " + i, messageConsumer.receive(5000));
+        }
+    }
+
+    private void publish(URI uri) throws Exception {
+        MessageProducer messageProducer = connectionFactory(uri).createConnection().createSession(false, Session.AUTO_ACKNOWLEDGE).createProducer(dest);
+        for (int i=0; i<NUM_MESSAGES; i++) {
+            messageProducer.send(new ActiveMQTextMessage());
+        }
+    }
+
+
+    private ActiveMQConnectionFactory connectionFactory(URI uri) {
+        ActiveMQConnectionFactory connectionFactory = new ActiveMQConnectionFactory(uri) {
+            @Override
+            public Connection createConnection() throws JMSException {
+                Connection connection = super.createConnection();
+                connections.add(connection);
+                // auto start!
+                connection.start();
+                return connection;
+            }
+        };
+        connectionFactory.setWatchTopicAdvisories(false);
+        return connectionFactory;
+    }
+
+    private BrokerService createBroker() {
+        BrokerService brokerService = new BrokerService();
+        brokerService.setBrokerName("B" + brokerServices.size());
+        brokerService.setBrokerId(brokerService.getBrokerName());
+        brokerService.setPersistent(false);
+        brokerService.setUseJmx(false);
+        brokerService.setAdvisorySupport(false);
+        brokerServices.add(brokerService);
+        return  brokerService;
+    }
+
+    @After
+    public void tearDown() throws Exception {
+        for (Connection connection : connections) {
+            try {
+                connection.close();
+            } catch (Exception ignored) {}
+        }
+        connections.clear();
+
+        for (BrokerService brokerService : brokerServices) {
+            try {
+                brokerService.stop();
+            } catch (Exception ignored) {}
+        }
+        brokerServices.clear();
+    }
+
+}