public boolean putServiceMapping(String service, String component) {
    if (containsMapping(service, component)) {
      return false;
    } else {
      serviceMapping.add(new KerberosKeytabServiceMappingEntity(this, service, component));
      return true;
    }
  }
Service mappings must be fetched {@link FetchType#EAGER} since they are
required when processing {@link KerberosKeytabPrincipalEntity} instances
and turning them into {@link ResolvedKerberosPrincipal}.
ambari-server/src/main/java/org/apache/ambari/server/orm/entities/KerberosKeytabPrincipalEntity.java