1/* Part of SWI-Prolog 2 3 Author: Jan Wielemaker 4 E-mail: J.Wielemaker@vu.nl 5 WWW: http://www.swi-prolog.org 6 Copyright (c) 2006-2016, University of Amsterdam 7 VU University Amsterdam 8 All rights reserved. 9 10 Redistribution and use in source and binary forms, with or without 11 modification, are permitted provided that the following conditions 12 are met: 13 14 1. Redistributions of source code must retain the above copyright 15 notice, this list of conditions and the following disclaimer. 16 17 2. Redistributions in binary form must reproduce the above copyright 18 notice, this list of conditions and the following disclaimer in 19 the documentation and/or other materials provided with the 20 distribution. 21 22 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 23 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 24 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 25 FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 26 COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 27 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 28 BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 29 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 30 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 32 ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 33 POSSIBILITY OF SUCH DAMAGE. 34*/ 35 36:- module(http_error, 37 [ 38 ]). 39:- use_module(library(prolog_stack)). 40:- use_module(library(settings)). 41:- use_module(library(broadcast)). 42:- use_module(library(debug)).

Decorate uncaught HTTP exceptions with stack-trace

This module decorates uncaught exceptions of the user code with a full stack-trace and sends error reports to the Prolog console. The behaviour can be controlled by

nodebug(http(error)): After disabling the http(error) debug channal, errors are only sent to the client. See nodebug/1 and debug/1.
set_setting(http:client_backtrace, false): Stop sending stack traces to the client. Note that sending the stack trace to the client simplifies debugging, it also provides clues to hackers on how to compromise your site. The more information you give them, the easier it is to break into your server! See set_setting/2 and set_setting_default/2. */

61:- setting(http:client_backtrace, boolean, true, 62 'Make backtrace visible to the client'). 63 64 65 /******************************* 66 * LOG ERRORS TO STDERR * 67 *******************************/ 68 69:- debug(http(error)). 70 71:- listen(http(Message), 72 http_listen(Message)). 73 74:- dynamic 75 saved_request/2. 76 77http_listen(_) :- 78 \+ debugging(http(error)), 79 !. 80http_listen(request_start(Id, Request)) :- 81 !, 82 asserta(saved_request(Id, Request)). 83http_listen(request_finished(Id, Code, Status, _CPU, _Bytes)) :- 84 retract(saved_request(Id, Request)), 85 !, 86 Code >= 400, 87 memberchk(path(Path), Request), 88 memberchk(method(Method), Request), 89 upcase_atom(Method, UMethod), 90 reply_status(Status, Reply), 91 debug(http(error), 92 '~w ~w: [~w] ~w', [UMethod, Path, Code, Reply]). 93 94reply_status(Status, Reply) :- 95 map_exception(Status, Reply), 96 !. 97reply_status(Status, Message) :- 98 message_to_string(Status, Message). 99 100map_exception(http_reply(bytes(ContentType,Bytes),_), bytes(ContentType,L)) :- 101 string_length(Bytes, L). % also does lists 102map_exception(http_reply(Reply), Reply). 103map_exception(http_reply(Reply, _), Reply). 104map_exception(error(existence_error(http_location, Location), _Stack), 105 error(404, Location)). 106 107 108 /******************************* 109 * DECORATE STACK TRACES * 110 *******************************/ 111 112:- dynamic prolog_stack:stack_guard/1. 113:- multifile prolog_stack:stack_guard/1. 114 115prolog_stack:stack_guard(httpd_wrapper:wrapper/5). 116prolog_stack:stack_guard(httpd_wrapper:handler_with_output_to/5)