Log warning when calling Channel#basicCancel with unknown tag

Fixes rabbitmq#528

Author: acogoluegnes

src/main/java/com/rabbitmq/client/Channel.java

@@ -15,18 +15,14 @@
 
 package com.rabbitmq.client;
 
+import com.rabbitmq.client.AMQP.BasicProperties;
+import com.rabbitmq.client.AMQP.*;
+
 import java.io.IOException;
 import java.util.Map;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.TimeoutException;
 
-import com.rabbitmq.client.AMQP.BasicProperties;
-import com.rabbitmq.client.AMQP.Exchange;
-import com.rabbitmq.client.AMQP.Queue;
-import com.rabbitmq.client.AMQP.Tx;
-import com.rabbitmq.client.AMQP.Basic;
-import com.rabbitmq.client.AMQP.Confirm;
-
 /**
  * Interface to a channel. All non-deprecated methods of
  * this interface are part of the public API.
@@ -1220,8 +1216,11 @@ void basicNack(long deliveryTag, boolean multiple, boolean requeue)
  /**
  * Cancel a consumer. Calls the consumer's {@link Consumer#handleCancelOk}
  * method.
+ * <p>
+ * A consumer tag that does not match any consumer is ignored.
+ *
  * @param consumerTag a client- or server-generated consumer tag to establish context
- * @throws IOException if an error is encountered, or if the consumerTag is unknown
+ * @throws IOException if an error is encountered
  * @see com.rabbitmq.client.AMQP.Basic.Cancel
  * @see com.rabbitmq.client.AMQP.Basic.CancelOk
  */

src/main/java/com/rabbitmq/client/impl/ChannelN.java

@@ -1468,8 +1468,10 @@ public void basicCancel(final String consumerTag)
  throws IOException
  {
  final Consumer originalConsumer = _consumers.get(consumerTag);
- if (originalConsumer == null)
- throw new IOException("Unknown consumerTag");
+ if (originalConsumer == null) {
+ LOGGER.warn("Tried to cancel consumer with unknown tag {}", consumerTag);
+ return;
+ }
 
  final Method m = new Basic.Cancel(consumerTag, false);
  BlockingRpcContinuation<Consumer> k = new BlockingRpcContinuation<Consumer>(m) {

src/test/java/com/rabbitmq/client/test/ChannelNTest.java

@@ -22,7 +22,6 @@
 import org.junit.Test;
 import org.mockito.Mockito;
 
-import java.io.IOException;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 
@@ -51,8 +50,8 @@ public void serverBasicCancelForUnknownConsumerDoesNotThrowException() throws Ex
  channel.processAsync(new AMQCommand(method));
  }
 
- @Test(expected = IOException.class)
- public void callingBasicCancelForUnknownConsumerThrowsException() throws Exception {
+ @Test
+ public void callingBasicCancelForUnknownConsumerDoesNotThrowException() throws Exception {
  AMQConnection connection = Mockito.mock(AMQConnection.class);
  ChannelN channel = new ChannelN(connection, 1, consumerWorkService);
  channel.basicCancel("does-not-exist");