HBASE-8539 Double(or tripple ...) ZooKeeper listeners of the same type when Master recovers from ZK SessionExpiredException (Jeffrey Zhong)

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1482574 13f79535-47bb-0310-9956-ffa450edef68

hbase-client/src/main/java/org/apache/hadoop/hbase/zookeeper/ZooKeeperWatcher.java

@@ -250,6 +250,20 @@ public class ZooKeeperWatcher implements Watcher, Abortable, Closeable {
     listeners.remove(listener);
   }
 
+  /**
+   * Clean all existing listeners
+   */
+  public void unregisterAllListeners() {
+    listeners.clear();
+  }
+
+  /**
+   * @return The number of currently registered listeners
+   */
+  public int getNumberOfListeners() {
+    return listeners.size();
+  }
+
   /**
    * Get the connection to ZooKeeper.
    * @return connection reference to zookeeper

hbase-server/src/main/java/org/apache/hadoop/hbase/master/HMaster.java

@@ -2017,6 +2017,7 @@ MasterServices, Server {
   private boolean tryRecoveringExpiredZKSession() throws InterruptedException,
       IOException, KeeperException, ExecutionException {
 
+    this.zooKeeper.unregisterAllListeners();
     this.zooKeeper.reconnectAfterExpiration();
 
     Callable<Boolean> callable = new Callable<Boolean> () {

hbase-server/src/test/java/org/apache/hadoop/hbase/TestZooKeeper.java

@@ -473,6 +473,8 @@ public class TestZooKeeper {
     MiniHBaseCluster cluster = TEST_UTIL.getHBaseCluster();
     cluster.startRegionServer();
     HMaster m = cluster.getMaster();
+    ZooKeeperWatcher zkw = m.getZooKeeperWatcher();
+    int expectedNumOfListeners = zkw.getNumberOfListeners();
     // now the cluster is up. So assign some regions.
     HBaseAdmin admin = new HBaseAdmin(TEST_UTIL.getConfiguration());
     byte[][] SPLIT_KEYS = new byte[][] { Bytes.toBytes("a"), Bytes.toBytes("b"),
@@ -490,6 +492,8 @@ public class TestZooKeeper {
     // The recovered master should not call retainAssignment, as it is not a
     // clean startup.
     assertFalse("Retain assignment should not be called", MockLoadBalancer.retainAssignCalled);
+    // number of listeners should be same as the value before master aborted
+    assertEquals(expectedNumOfListeners, zkw.getNumberOfListeners());
   }
 
   /**