@Override public void start() { LOG.info("QueryMaster start"); queryHeartbeatThread = new QueryHeartbeatThread(); queryHeartbeatThread.start(); clientSessionTimeoutCheckThread = new ClientSessionTimeoutCheckThread(); clientSessionTimeoutCheckThread.start(); finishedQueryMasterTaskCleanThread = new FinishedQueryMasterTaskCleanThread(); finishedQueryMasterTaskCleanThread.start(); super.start(); }