// metrics system init is really init & start.
// It's more test friendly to put it here.
DefaultMetricsSystem.initialize("DAGAppMaster");
this.appsStartTime = clock.getTime();
AMStartedEvent startEvent = new AMStartedEvent(appAttemptID,
startTime, appsStartTime, appSubmitTime);
dispatcher.getEventHandler().handle(
new DAGHistoryEvent(startEvent));
this.lastDAGCompletionTime = clock.getTime();