@Override
  public boolean equals(Object o) {
    if (this == o) return true;
    if (o == null || getClass() != o.getClass()) return false;

    TopologyUpdateEvent that = (TopologyUpdateEvent) o;

    return Objects.equals(eventType, that.eventType) &&
      Objects.equals(clusters, that.clusters);
  }
Type of update, is used to differ full current topology (CREATE), adding new or update existing topology
elements (UPDATE) and removing existing topology elements (DELETE).
ambari-server/src/main/java/org/apache/ambari/server/events/TopologyUpdateEvent.java