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Rework the timeout of the CGI script.

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The previous implementation was fine to catch timeout of third-party
tools (like dot), but to good to catch timeout in Spot itself, because
Python will not deliver a SIGALRM while a native function (e.g. Spot's
translation) is running.  So we fork() the Python process, with a
parent that does nothing but wait for the termination of the child or
for an alarm.  On SIGALRM, the parent kills all children.

* wrap/python/ajax/spot.in: Adjust to fork.
* wrap/python/tests/alarm.py: New test file to test this
scenario in a more controled environment.
* wrap/python/tests/Makefile.am: Add it.
This commit is contained in:
Alexandre Duret-Lutz 2012-06-04 16:38:42 +02:00
parent 75862a3284
commit 7b7a946485
4 changed files with 86 additions and 7 deletions
Download patch file Download diff file Expand all files Collapse all files

4
NEWS
View file

@ -1,6 +1,8 @@
New in spot 0.9.1a:
Nothing yet.
* Bug fixes:
- The CGI script running for ltl2tgba.html will correctly timeout
after 30s when Spot's translation takes more time.
New in spot 0.9.1 (2012-05-23):

18
wrap/python/ajax/spot.in
View file

@ -220,16 +220,12 @@ If you want to benchmark big formulae it is
better to install Spot on your own computer.</p>\n""")
finish(kill = True)
def reset_alarm():
signal.alarm(30)
def run_dot(basename, ext):
outname = basename + '.' + ext
# Do not call "dot" to generate a file that already exists.
if not os.access(outname, os.F_OK):
os.spawnlp(os.P_WAIT, dot, dot, dot_bgcolor, '-T' + ext,
'-Gsize=8.2,8.2', '-o', outname, basename + '.txt')
reset_alarm()
# Create a unused hardlink that points to the output picture
# just to remember how many cache entries are sharing it.
os.link(outname, tmpdir + "/" + ext)
@ -344,8 +340,20 @@ if output_type == 'v':
spot.unblock_signal(signal.SIGALRM)
spot.unblock_signal(signal.SIGTERM)
os.setpgrp()
child = os.fork()
if child != 0:
# In parent. We are just waiting for the termination of the
# child, or for the timeout alarm. On SIGALRM, we will kill the
# child.
#
# We cannot avoid forking, because Python will not deliver a
# signal when a C function is running. So if Spot takes too long
# to translate some formula, it would not get interrupted.
signal.signal(signal.SIGALRM, alarm_handler)
reset_alarm()
signal.alarm(30)
os.waitpid(child, 0)
exit(0)
# Global options
utf8 = False

1
wrap/python/tests/Makefile.am
View file

@ -30,6 +30,7 @@ TESTS_ENVIRONMENT = ./run
check_SCRIPTS = run
TESTS = \
alarm.py \
ltlsimple.py \
ltlparse.py \
bddnqueen.py \

68
wrap/python/tests/alarm.py Executable file
View file

@ -0,0 +1,68 @@
# -*- mode: python; coding: utf-8 -*-
# Copyright (C) 2012 Laboratoire de Recherche et Développement
# de l'Epita
#
# This file is part of Spot, a model checking library.
#
# Spot is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# Spot is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
# License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Spot; see the file COPYING. If not, write to the Free
# Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
# 02111-1307, USA.
import spot
import time
import signal
import sys
import os
def alarm_handler(signum, frame):
sys.stdout.write("signaled\n")
os.kill(child, signal.SIGTERM)
exit(0)
f = """!(G(F(P_Rbt2.observe)&& F(P_Rbt3.observe) &&
F(P_rbt1.observe)&& F(P_Rbt1.plus || P_Rbt1.moins || P_Rbt1.stop)&&
F(P_Rbt3.plus || P_Rbt3.moins || P_Rbt3.stop) && F(P_Rbt2.plus ||
P_Rbt2.moins || P_Rbt2.stop))-> G((F "map[0]==1") && (F "map[1]==1")
&& (F "map[2]==1") && (F "map[3]==1") && (F "map[4]==1") && (F
"map[5]==1") && (F "map[6]==1") && (F "map[7]==1") && (F "map[8]==1")
&& (F "map[9]==1") && (F "map[0]==2") && (F "map[1]==2") && (F
"map[2]==2") && (F "map[3]==2") && (F "map[4]==2") && (F "map[5]==2")
&& (F "map[6]==2") && (F "map[7]==2") && (F "map[8]==2") && (F
"map[9]==2") && (F "map[0]==3") && (F "map[1]==3") && (F "map[2]==3")
&& (F "map[3]==3") && (F "map[4]==3") && (F "map[5]==3") && (F
"map[6]==3") && (F "map[7]==3") && (F "map[8]==3") && (F
"map[9]==3")))"""
e = spot.default_environment.instance()
p = spot.empty_parse_error_list()
f = spot.parse(f, p, e)
d = spot.bdd_dict()
spot.unblock_signal(signal.SIGALRM)
spot.unblock_signal(signal.SIGTERM)
os.setpgrp()
child = os.fork()
if child != 0:
signal.signal(signal.SIGALRM, alarm_handler)
signal.alarm(2)
os.waitpid(child, 0)
# If the child returns, before we get the alarm it's a bug.
exit(1)
# This is expected to take WAY more that 2s.
print "Before"
spot.ltl_to_tgba_fm(f, d, True)
print "After"
exit(1)