private GroupEntity getCachedGroupByPrincipal(PrincipalEntity principalEntity) {
    GroupEntity entity = groupsCache.get().getIfPresent(principalEntity);
    if (entity == null) {
      for (GroupEntity groupEntity : groupDAO.findAll()) {
        groupsCache.get().put(groupEntity.getPrincipal(), groupEntity);
      }
      entity = groupsCache.get().getUnchecked(principalEntity);
    }
    return entity;
  }
The key property ids for a privilege resource.
ambari-server/src/main/java/org/apache/ambari/server/controller/internal/UserPrivilegeResourceProvider.java