@PUT @ApiIgnore // until documented
  @Path("{upgradeItemId}")
  @Produces("text/plain")
  public Response updateUpgradeItem(String body,
                                    @Context HttpHeaders headers,
                                    @Context UriInfo ui, @PathParam("upgradeItemId") Long id) {
    return handleRequest(headers, body, ui, Request.Type.PUT, createResourceInstance(id));
  }
Handles:
PUT /clusters/{clusterId}/upgrades/{upgradeId}/upgrade_groups/{upgradeGroupId}/upgrade_items/{upgradeItemId}

Change state of existing upgrade item.

@param body     http body
@param headers  http headers
@param ui       uri info
@param id       the upgrade item id

@return information regarding the created services
ambari-server/src/main/java/org/apache/ambari/server/api/services/UpgradeItemService.java