void start() throws InterruptedException {
   if (dependencies.size() > 0) {
     synchronized (this) {
       while (!canStart) {
         this.wait(1000 * 60 * 3L);
         if (dependenciesFailed) {
           throw new TezUncheckedException(
               "Skipping service start for "
                   + service.getName()
                   + " as dependencies failed to start");
         }
       }
     }
   }
   if (LOG.isDebugEnabled()) {
     LOG.debug("Service: " + service.getName() + " trying to start");
   }
   for (Service dependency : dependencies) {
     if (!dependency.isInState(Service.STATE.STARTED)) {
       LOG.info(
           "Service: "
               + service.getName()
               + " not started because "
               + " service: "
               + dependency.getName()
               + " is in state: "
               + dependency.getServiceState());
       return;
     }
   }
   service.start();
 }
 @Override
 public void stateChanged(Service dependency) {
   if (LOG.isDebugEnabled()) {
     LOG.debug(
         "Service dependency: "
             + dependency.getName()
             + " notify"
             + " for service: "
             + service.getName());
   }
   if (dependency.isInState(Service.STATE.STARTED)) {
     if (dependenciesStarted.incrementAndGet() == dependencies.size()) {
       synchronized (this) {
         if (LOG.isDebugEnabled()) {
           LOG.debug("Service: " + service.getName() + " notified to start");
         }
         canStart = true;
         this.notifyAll();
       }
     }
   } else if (!service.isInState(Service.STATE.STARTED)
       && dependency.getFailureState() != null) {
     synchronized (this) {
       dependenciesFailed = true;
       if (LOG.isDebugEnabled()) {
         LOG.debug(
             "Service: "
                 + service.getName()
                 + " will fail to start"
                 + " as dependent service "
                 + dependency.getName()
                 + " failed to start");
       }
       this.notifyAll();
     }
   }
 }