@Override
  public int hashCode() {
    int result = hostId != null ? hostId.hashCode() : 0;
    result = 31 * result + (clusters != null ? clusters.hashCode() : 0);
    return result;
  }
Execution commands grouped by cluster id.
ambari-server/src/main/java/org/apache/ambari/server/events/ExecutionCommandEvent.java