@Override
  public void setStateChangeListener(SchedulerStateChangeListener listener) {
    this.listener = listener;
  }
Scheduler class invoked by each processor to check if the leader is alive.
Checks every 30 seconds.
If a processor row hasn't been updated since 30 seconds, the system assumes that the processor has died.
All time units are in SECONDS.
samza-azure/src/main/java/org/apache/samza/coordinator/scheduler/LeaderLivenessCheckScheduler.java