code: public void prepareFailover() {
      if (!RemoteJTProxy.isJTRestartingEnabled(conf)) {
        return;
      }
      
      LOG.info("prepareFailover done");
      
      this.isPurgingJob = false;
      
      if (this.parentHeartbeat != null) {
        // Because our failover mechanism based on remotJTProxy can't 
        // reach remote job tracker, we stop the interTrackerServer to
        // trigger the failover
        this.interTrackerServer.stop();
      }
    }
docs: Some perparation job needed by remote job tracker for
  failover