private void onEventComplete(Event event) {
    synchronized (listeners) {
      for (EventListener listener : listeners) {
        try {
          listener.onEventComplete(this, event);
        } catch (Exception ee) {
          // too bad.
        }
      }
    }
  }
Notify listeners of events.
<p/>
Please *do not* write tests that check for events *not* arriving. Events will not arrive if there was an exception
in the function that triggers the event or inside this function.
@param event the {@link Event} that just occurred.
ambry-test-utils/src/main/java/com/github/ambry/rest/MockRestRequest.java