synchronized boolean timedOut(int maxIdleTime) {
      long timeoutTime = lastAccessTime + maxIdleTime;
      if (EnvironmentEdgeManager.currentTime() > timeoutTime) {
        connections.remove(userName);
        closed = true;
        return true;
      }
      return false;
    }
Returns Cluster ID for the HBase cluster or null if there is an err making the connection.
hbase-server/src/main/java/org/apache/hadoop/hbase/util/ConnectionCache.java