Stop all producer tasks and close connections

Stopping all the tasks and then close connections (instead of stop a
task and then close the corresponding connection) at least stop
publishing as soon as possible in case a connection takes some time to
close.

Publisher connections can take some time to close because of flow
control. In this case, even though all publishing tasks are terminated,
a significant amount of messages can still seem to be sent probably because of
TCP buffers flushing. So this commit can help mitigate this phenomenon,
but not completely prevent it. Using Connection#close(int timeout) should not
help either TCP buffer flushing would also occur.

[#157183370]

Fixes #96

Author: acogoluegnes

src/main/java/com/rabbitmq/perf/MulticastSet.java

@@ -182,20 +182,17 @@ public void run(boolean announceStartup)
 
         this.completionHandler.waitForCompletion();
 
-        int count = 1; // counting the threads
-        for (int i = 0; i < producerStates.length; i++) {
-            producerStates[i].task.cancel(true);
-            if(count % params.getProducerChannelCount() == 0) {
-                // this is the end of a group of threads on the same connection,
-                // closing the connection
-                try {
-                    producerConnections[count / params.getProducerChannelCount() - 1].close();
-                } catch (Exception e) {
-                    // don't do anything, we need to close the other connections
-                }
+        for (AgentState producerState : producerStates) {
+            producerState.task.cancel(true);
+        }
 
+        for (Connection producerConnection : producerConnections) {
+            try {
+                producerConnection.close();
+            } catch (Exception e) {
+                // don't do anything, we need to close the other connections
             }
-            count++;
+
         }
 
         for (Connection consumerConnection : consumerConnections) {