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

    ExecutionCommandEvent that = (ExecutionCommandEvent) o;

    if (hostId != null ? !hostId.equals(that.hostId) : that.hostId != null) return false;
    return clusters != null ? clusters.equals(that.clusters) : that.clusters == null;
  }
Execution commands grouped by cluster id.
ambari-server/src/main/java/org/apache/ambari/server/events/ExecutionCommandEvent.java