public ServiceComponentHostEventWrapper getFsmEvent(String hostname, String roleStr) {
    return hostRoleCommands.get(getSafeHost(hostname)).get(roleStr).getEvent();
  }
@param hostname    the hostname; {@code null} for a server-side stage
@param roleStr     the role name
@return the wrapper event
ambari-server/src/main/java/org/apache/ambari/server/actionmanager/Stage.java