public AlertDefinitionEntity getAlertDefinition() {
    return alertDefinition;
  }
Gets the associated alert definition for this alert instance. The alert
definition can be used to retrieve global information about an alert such
as the interval and the name.

@return the alert definition (never {@code null}).
ambari-server/src/main/java/org/apache/ambari/server/orm/entities/AlertHistoryEntity.java