code: @Override
    public synchronized void handleEvent(final Event event) {
      if (event.getType() == EventType.FLOW_FINISHED) {
        final FlowRunner runner = (FlowRunner) event.getRunner();
        if (runner != null && runner.getExecutableFlow().getStatus().equals(Status.FAILED)) {
          this.value = this.value + 1;
        }
      }
    }
docs: Listen for events to maintain correct value of number of failed flows {@inheritDoc}
  
  @see azkaban.event.EventListener#handleEvent(azkaban.event.Event)