docs: @LifecycleStart
    @Override
    public void start() throws Exception
    {
      super.start();
  
      synchronized (lifecycleLock) {
        Preconditions.checkState(!started, "already started");
        started = true;
  
        try {
          cleanupStaleAnnouncements();
          registerRunListener();
          pathChildrenCache.start();
  
          log.info("Started WorkerTaskMonitor.");
          started = true;
        }
        catch (InterruptedException e) {
          throw e;
        }
        catch (Exception e) {
          log.makeAlert(e, "Exception starting WorkerTaskMonitor")
             .emit();
          throw e;
        }
      }
    }