GH-1034: DMLC: Detect target channel changed

Fixes #1034

If the connection factory refreshed the target connection, the DMLC
is not made aware of it and so we never consume from the new channel.

**cherry-pick to all 2.x**

Author: garyrussell

spring-rabbit/src/main/java/org/springframework/amqp/rabbit/listener/DirectMessageListenerContainer.java

@@ -47,6 +47,7 @@
 import org.springframework.amqp.core.Message;
 import org.springframework.amqp.core.MessageProperties;
 import org.springframework.amqp.core.Queue;
+import org.springframework.amqp.rabbit.connection.ChannelProxy;
 import org.springframework.amqp.rabbit.connection.Connection;
 import org.springframework.amqp.rabbit.connection.ConnectionFactory;
 import org.springframework.amqp.rabbit.connection.ConnectionFactoryUtils;
@@ -473,7 +474,8 @@ private void checkConsumers(long now) {
 		synchronized (this.consumersMonitor) {
 			consumersToCancel = this.consumers.stream()
 					.filter(consumer -> {
-						boolean open = consumer.getChannel().isOpen() && !consumer.isAckFailed();
+						boolean open = consumer.getChannel().isOpen() && !consumer.isAckFailed()
+								&& !consumer.targetChanged();
 						if (open && this.messagesPerAck > 1) {
 							try {
 								consumer.ackIfNecessary(now);
@@ -871,6 +873,8 @@ final class SimpleConsumer extends DefaultConsumer {
 
 		private final long ackTimeout = DirectMessageListenerContainer.this.ackTimeout;
 
+		private final Channel targetChannel;
+
 		private int pendingAcks;
 
 		private long lastAck = System.currentTimeMillis();
@@ -889,11 +893,17 @@ final class SimpleConsumer extends DefaultConsumer {
 
 		private volatile boolean ackFailed;
 
-		private SimpleConsumer(Connection connection, Channel channel, String queue) {
+		SimpleConsumer(Connection connection, Channel channel, String queue) {
 			super(channel);
 			this.connection = connection;
 			this.queue = queue;
 			this.ackRequired = !getAcknowledgeMode().isAutoAck() && !getAcknowledgeMode().isManual();
+			if (channel instanceof ChannelProxy) {
+				this.targetChannel = ((ChannelProxy) channel).getTargetChannel();
+			}
+			else {
+				this.targetChannel = null;
+			}
 		}
 
 		private String getQueue() {
@@ -930,6 +940,15 @@ boolean isAckFailed() {
 			return this.ackFailed;
 		}
 
+		/**
+		 * True if the channel is a proxy and the underlying channel has changed.
+		 * @return true if the condition exists.
+		 */
+		boolean targetChanged() {
+			return this.targetChannel != null
+					&& !((ChannelProxy) getChannel()).getTargetChannel().equals(this.targetChannel);
+		}
+
 		/**
 		 * Increment and return the current epoch for this consumer; consumersMonitor must
 		 * be held.

spring-rabbit/src/test/java/org/springframework/amqp/rabbit/listener/DirectMessageListenerContainerMockTests.java

@@ -41,6 +41,7 @@
 import org.junit.Test;
 import org.mockito.Mockito;
 
+import org.springframework.amqp.core.AcknowledgeMode;
 import org.springframework.amqp.core.MessageListener;
 import org.springframework.amqp.rabbit.connection.ChannelProxy;
 import org.springframework.amqp.rabbit.connection.Connection;
@@ -175,7 +176,7 @@ else if (i.getArgument(0).equals(17L)) {
 		}
 		Thread.sleep(200);
 		consumer.get().handleDelivery("consumerTag", envelope(16), props, body);
-		// should get 2 acks #10 and #6 (timeout)
+		// should get 2 acks #10 and #16 (timeout)
 		assertThat(latch2.await(10, TimeUnit.SECONDS)).isTrue();
 		consumer.get().handleDelivery("consumerTag", envelope(17), props, body);
 		verify(channel).basicAck(10L, true);
@@ -309,6 +310,56 @@ public void testMonitorCancelsAfterBadAckEvenIfChannelReportsOpen() throws Excep
 		container.stop();
 	}
 
+	@Test
+	public void testMonitorCancelsAfterTargetChannelChanges() throws Exception {
+		ConnectionFactory connectionFactory = mock(ConnectionFactory.class);
+		Connection connection = mock(Connection.class);
+		ChannelProxy channel = mock(ChannelProxy.class);
+		Channel rabbitChannel1 = mock(Channel.class);
+		Channel rabbitChannel2 = mock(Channel.class);
+		AtomicReference<Channel> target = new AtomicReference<>(rabbitChannel1);
+		willAnswer(inv -> {
+			return target.get();
+		}).given(channel).getTargetChannel();
+
+		given(connectionFactory.createConnection()).willReturn(connection);
+		given(connection.createChannel(anyBoolean())).willReturn(channel);
+		given(channel.isOpen()).willReturn(true);
+		given(channel.queueDeclarePassive(Mockito.anyString()))
+				.willAnswer(invocation -> mock(AMQP.Queue.DeclareOk.class));
+		AtomicReference<Consumer> consumer = new AtomicReference<>();
+		final CountDownLatch latch1 = new CountDownLatch(1);
+		final CountDownLatch latch2 = new CountDownLatch(1);
+		willAnswer(inv -> {
+			consumer.set(inv.getArgument(6));
+			latch1.countDown();
+			return "consumerTag";
+		}).given(channel).basicConsume(anyString(), anyBoolean(), anyString(), anyBoolean(), anyBoolean(),
+						anyMap(), any(Consumer.class));
+
+		willAnswer(inv -> {
+			consumer.get().handleCancelOk("consumerTag");
+			latch2.countDown();
+			return null;
+		}).given(channel).basicCancel("consumerTag");
+
+		DirectMessageListenerContainer container = new DirectMessageListenerContainer(connectionFactory);
+		container.setQueueNames("test");
+		container.setPrefetchCount(2);
+		container.setMonitorInterval(100);
+		container.setMessageListener(msg -> {
+			target.set(rabbitChannel2);
+		});
+		container.setAcknowledgeMode(AcknowledgeMode.MANUAL);
+		container.afterPropertiesSet();
+		container.start();
+
+		assertThat(latch1.await(10, TimeUnit.SECONDS)).isTrue();
+		consumer.get().handleDelivery("consumerTag", envelope(1L), new BasicProperties(), new byte[1]);
+		assertThat(latch2.await(10, TimeUnit.SECONDS)).isTrue();
+		container.stop();
+	}
+
 	private Envelope envelope(long tag) {
 		return new Envelope(tag, false, "", "");
 	}