@Override
  public void shutdown() {
    LOG.info("Shutting down LivenessCheckScheduler Scheduler.");
    scheduler.shutdownNow();
  }
Scheduler class invoked by the leader to check for changes in the list of live processors.
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/LivenessCheckScheduler.java