@Override
  public void init(MetricsConfiguration configuration, MetricsSink sink) {
    super.init(configuration, sink);
    for (STOMPEvent.Type type : STOMPEvent.Type.values()) {
      events.put(type, 0L);
    }

  }
Collects metrics about number of events by types and publishes to configured Metric Sink.
ambari-server/src/main/java/org/apache/ambari/server/metrics/system/impl/StompEventsMetricsSource.java