@GET @ApiIgnore // until documented
  @Produces("text/plain")
  public Response getHistories(@Context HttpHeaders headers,
      @Context UriInfo ui) {
    return handleRequest(headers, null, ui, Request.Type.GET,
        createResourceInstance(clusterName, null));
  }
Constructor.

@param clusterName
         the cluster name (not {@code null}).
@param serviceName
         the service name, or {@code null} to return history across all
         services.
@param hostName
         the host name, or {@code null} to return history across all hosts.
ambari-server/src/main/java/org/apache/ambari/server/api/services/AlertHistoryService.java