[issue #670]change the way to create newGroupChannelTable (#1412)

* change the way to create newGroupChannelTable

broker/src/main/java/org/apache/rocketmq/broker/client/ProducerManager.java

@@ -53,7 +53,15 @@ public class ProducerManager {
         try {
             if (this.groupChannelLock.tryLock(LOCK_TIMEOUT_MILLIS, TimeUnit.MILLISECONDS)) {
                 try {
-                    newGroupChannelTable.putAll(groupChannelTable);
+                    Iterator<Map.Entry<String, HashMap<Channel, ClientChannelInfo>>> iter = groupChannelTable.entrySet().iterator();
+                    while (iter.hasNext()) {
+                        Map.Entry<String, HashMap<Channel, ClientChannelInfo>> entry = iter.next();
+                        String key = entry.getKey();
+                        HashMap<Channel, ClientChannelInfo> val = entry.getValue();
+                        HashMap<Channel, ClientChannelInfo> tmp = new HashMap<Channel, ClientChannelInfo>();
+                        tmp.putAll(val);
+                        newGroupChannelTable.put(key, tmp);
+                    }
                 } finally {
                     groupChannelLock.unlock();
                 }

broker/src/test/java/org/apache/rocketmq/broker/client/ProducerManagerTest.java

@@ -87,4 +87,12 @@ public class ProducerManagerTest {
         assertThat(channelMap).isNull();
     }
 
+    @Test
+    public void testGetGroupChannelTable() throws Exception {
+        producerManager.registerProducer(group, clientInfo);
+        HashMap<Channel, ClientChannelInfo> oldMap = producerManager.getGroupChannelTable().get(group);
+        
+        producerManager.unregisterProducer(group, clientInfo);
+        assertThat(oldMap.size()).isNotEqualTo(0);
+    }
 }
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