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

    AlertDefinitionsAgentUpdateEvent other = (AlertDefinitionsAgentUpdateEvent) o;

    return Objects.equals(eventType, other.eventType) &&
      Objects.equals(clusters, other.clusters);
  }
Contains info about alert definitions update. This update is specific to a single host.
ambari-server/src/main/java/org/apache/ambari/server/events/AlertDefinitionsAgentUpdateEvent.java