@PUT
  @Path("{requestId}")
  @Produces(MediaType.TEXT_PLAIN)
  @ApiOperation(value = "Updates a request, usually used to cancel running requests.",
      notes = "Changes the state of an existing request. Usually used to cancel running requests.",
      nickname = "RequestService#updateRequests"
  )
  @ApiImplicitParams({
      @ApiImplicitParam(dataType = REQUEST_PUT_REQUEST_TYPE, paramType = PARAM_TYPE_BODY)
  })
  @ApiResponses({
      @ApiResponse(code = HttpStatus.SC_OK, message = MSG_SUCCESSFUL_OPERATION),
      @ApiResponse(code = HttpStatus.SC_ACCEPTED, message = MSG_REQUEST_ACCEPTED),
      @ApiResponse(code = HttpStatus.SC_BAD_REQUEST, message = MSG_INVALID_ARGUMENTS),
      @ApiResponse(code = HttpStatus.SC_NOT_FOUND, message = MSG_RESOURCE_NOT_FOUND),
      @ApiResponse(code = HttpStatus.SC_UNAUTHORIZED, message = MSG_NOT_AUTHENTICATED),
      @ApiResponse(code = HttpStatus.SC_FORBIDDEN, message = MSG_PERMISSION_DENIED),
      @ApiResponse(code = HttpStatus.SC_INTERNAL_SERVER_ERROR, message = MSG_SERVER_ERROR),
  })
  public Response updateRequests(String body, @Context HttpHeaders headers, @Context UriInfo ui,
                                 @ApiParam @PathParam("requestId") String requestId) {
    return handleRequest(headers, body, ui, Request.Type.PUT, createRequestResource(m_clusterName, requestId));
  }
Handles: PUT /clusters/{clusterId}/requests/{requestId} or /requests/{requestId}
Change state of existing requests. Usually used to cancel running requests

@param body        http body
@param headers     http headers
@param ui          uri info
@return information regarding the updated requests
ambari-server/src/main/java/org/apache/ambari/server/api/services/RequestService.java