mod_php vs context: tight loop

From: Brendan Jurd <brendan.jurd@achievecorp.com.au>
To: ntg-context@ntg.nl
Subject: mod_php vs context: tight loop
Date: Fri, 25 Nov 2011 16:12:19 +1100	[thread overview]
Message-ID: <4ECF23B3.4030005@achievecorp.com.au> (raw)

Hello list,

I have a PHP application which generates documentation on the fly with 
context.  This has been working really well, but I am now testing 
deployment on a new server with a more recent version of context, and it 
seems to be somehow getting itself into a tight loop.

When I run texexec via the mod_php apache module, the command never 
returns, and `ps ax` shows the following:

  9709 ?        S      0:00 sh -c texexec --check 2>&1
  9710 ?        S      0:00 /bin/sh /usr/bin/texexec --check
  9711 ?        R      9:59 /usr/bin/texlua /usr/bin/mtxrun --usekpse 
--execute texexec --check

`top` shows the mtxrun process eating 99.9% CPU.  Attaching an strace to 
this process, once it is underway, shows no output.

My test script is as follows:

<?php
$result = null;
system("texexec --check 2>&1", $result);
print $result . "\n";
?>

When this same test script is run directly from the command line with 
`php5 -f test.php`, it works as expected and outputs the following:

MTXrun | kpse fallback with progname 'context' initialized in 0.01 
secondsTeXExec | current distribution: web2c
TeXExec | context source date: 2010.07.30 11:35
TeXExec | format path: . /root/.texmf-config/web2c/luatex 
/root/.texmf-var/web2c/luatex /root/texmf/web2c/luatex 
/etc/texmf/web2c/luatex /var/lib/texmf/web2c/luatex 
/usr/local/share/texmf/web2c/luatex /usr/share/texmf/web2c/luatex 
/usr/share/texmf-texlive/web2c/luatex /root/.texmf-config/web2c 
/root/.texmf-var/web2c /root/texmf/web2c /etc/texmf/web2c 
/var/lib/texmf/web2c /usr/local/share/texmf/web2c /usr/share/texmf/web2c 
/usr/share/texmf-texlive/web2c
TeXExec | start of analysis
TeXExec | end of analysis
TeXExec |
TeXExec | TeXExec | version 6.2.1 - 1997-2009 - PRAGMA ADE/POD

0

Using --timeout=30 in the arguments to texexec makes no difference; 
mtxrun nonetheless runs forever until it is signalled.

It seems that this must be down to some kind of difference in Apache's 
execution environment -- I don't see any other way to explain the same 
PHP code working in cli and failing in mod_php, even when running as the 
same user.  But what possible environmental factor could lead to mtxrun 
freaking out like this?  I'm hoping someone on this list may be able to 
point me in the right direction.

This server is a VZ instance running under proxmox, with the following 
relevant ubuntu packages installed (per the 'natty' release):

context                 2010.07.30-1
libapache2-mod-php5     5.3.5-1ubuntu7.3
apache2                 2.2.17-1ubuntu1.4

-- 
Regards,
Brendan Jurd

Software Engineer
Achieve, Corp

brendan.jurd@achievecorp.com.au

___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the Wiki!

maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
webpage  : http://www.pragma-ade.nl / http://tex.aanhet.net
archive  : http://foundry.supelec.fr/projects/contextrev/
wiki     : http://contextgarden.net
___________________________________________________________________________________