Adding sanity check to ChannelManager.disconnectChannel...

... which leads to a testfailure that indicates that there is a race (or
similar problem) in Channel.close:

java.lang.IllegalStateException: We have attempted to create a disconnect a channel that's no longer in use. This should never happen. Please report this as a bug.
	at com.rabbitmq.client.impl.ChannelManager.disconnectChannel(ChannelManager.java:130)
	at com.rabbitmq.client.impl.AMQConnection.disconnectChannel(AMQConnection.java:117)
	at com.rabbitmq.client.impl.ChannelN.releaseChannelNumber(ChannelN.java:169)
	at com.rabbitmq.client.impl.ChannelN.close(ChannelN.java:365)
	at com.rabbitmq.client.impl.ChannelN.abort(ChannelN.java:307)
	at com.rabbitmq.client.impl.ChannelN.abort(ChannelN.java:300)
	at com.rabbitmq.client.test.BrokerTestCase.closeChannel(BrokerTestCase.java:124)
	at com.rabbitmq.client.test.BrokerTestCase.tearDown(BrokerTestCase.java:67)

Author: aschmolck

src/com/rabbitmq/client/impl/ChannelManager.java

@@ -66,12 +66,12 @@ public ChannelManager(int channelMax){
       channelNumberAllocator = new IntAllocator(1, channelMax);
     }
 
-    
+
     /**
      * Public API - Looks up an existing channel associated with this connection.
      * @param channelNumber the number of the required channel
      * @return the relevant channel descriptor
-     * @throws UnknownChannelException if there is no Channel associated with the 
+     * @throws UnknownChannelException if there is no Channel associated with the
      *         required channel number.
      */
     public ChannelN getChannel(int channelNumber) {
@@ -100,7 +100,7 @@ public synchronized ChannelN createChannel(AMQConnection connection) throws IOEx
     }
 
     public synchronized ChannelN createChannel(AMQConnection connection, int channelNumber) throws IOException {
-        if(channelNumberAllocator.reserve(channelNumber)) 
+        if(channelNumberAllocator.reserve(channelNumber))
             return createChannelInternal(connection, channelNumber);
         else
             return null;
@@ -110,10 +110,10 @@ private synchronized ChannelN createChannelInternal(AMQConnection connection, in
         if (_channelMap.containsKey(channelNumber)) {
             // That number's already allocated! Can't do it
             // This should never happen unless something has gone
-            // badly wrong with our implementation. 
+            // badly wrong with our implementation.
             throw new IllegalStateException("We have attempted to"
               + "create a channel with a number that is already in"
-              + "use. This should never happen. Please report this as a bug."); 
+              + "use. This should never happen. Please report this as a bug.");
         }
         ChannelN ch = new ChannelN(connection, channelNumber);
         addChannel(ch);
@@ -126,7 +126,12 @@ private void addChannel(ChannelN chan) {
     }
 
     public synchronized void disconnectChannel(int channelNumber) {
-        _channelMap.remove(channelNumber);
+        if (_channelMap.remove(channelNumber) == null)
+            throw new IllegalStateException(
+                "We have attempted to "
+                + "create a disconnect a channel that's no longer in "
+                + "use. This should never happen. Please report this as a bug.");
+        System.err.println("DISCONN CH" + channelNumber);
         channelNumberAllocator.free(channelNumber);
     }
 }