public void addAlertExecutionCommand(AlertExecutionCommand command) {
    // commands are added here when they are taken off the queue; there should
    // be no thread contention and thus no worry about locks for the null check
    if (null == alertExecutionCommands) {
      alertExecutionCommands = new ArrayList<>();
    }

    alertExecutionCommands.add(command);
  }
Sets the alert definition commands that contain the alert definitions for
each cluster that the host is a member of.

@param commands
         the commands, or {@code null} for none.
ambari-server/src/main/java/org/apache/ambari/server/agent/HeartBeatResponse.java