SPUG: Segmentation Fault in mod_perl

Stephen Nickels snickels at u.washington.edu
Thu Mar 15 13:42:56 CST 2001


Wow, I've never seen this before. What versions are being run when you see
this problem? I spent a summer with a bunch of boxes running mod_perl and
php on apache, and never saw a problem. My home box runs linux 2.4.2,
apache 1.3.12, php 4.0.1pl2 and mod_perl 1.24 and I've never had a
mod_perl problem connecting to a database.
I'm curious to know where and how you get these problems so I can watch
for them in the future....

--Steve


On Thu, 15 Mar 2001, John Cokos, CEO, iWeb, Inc. wrote:

> Although I'm not sure if this is related to the original
> problem, it's food for thought, nonetheless .....
>
> I've noticed a quite serious problem when you have
> php and mod_perl both compiled into apache.  The problems
> only arise when a mod_perl program attempts to
> connect to a database.  At that point, mod_perl programs
> start throwing up Segfaults, and php scripts start returning
> no data at all.
>
> Definitely a bug somewhere, where these 2 technologies
> are bumping into each other's shared memory or something.
>
> I've found that in every case, turning php "off" always fixes
> the mod_perl problem.  While not the best solution, it
> is the only solution when you're trying to do both.
>
> J-
>
> ========================================
>   John Cokos, President / CEO: iWeb Inc.
>   http://www.iwebsys.com
>   jcokos at ccs.net
> ========================================
> ----- Original Message -----
> From: "Richard Anderson" <Richard.Anderson at raycosoft.com>
> To: "John Cokos" <jcokos at iwebsys.com>; "Jonathan Gardner" <gardner at sounddomain.com>; <spug-list at pm.org>
> Cc: "Colin Meyer" <cmeyer at helvella.org>
> Sent: Tuesday, May 15, 2001 9:14 AM
> Subject: Re: SPUG: Segmentation Fault in mod_perl
>
>
> > I've done a bit of work on search engines, and I have a couple of thoughts:
> >
> > John pointed us toward a few potentential minor syntax problems.  The out-of-memory problem will pop up quite a bit if you are
> searching a large internap site like yahoo, yellowpages.com etc. and the search returns a lot of results.  Imagine seaching the NYC
> phonebook for the string Smith!
> >
> > One try might be to use a more memory-efficient XML parser routine.  Damian is probably a good resource on this (are you out
> there, mate?).
> >
> > Another approach is to limit your search to returning the first 50 results you find.  If the user wants more results, add a link
> at the top and bottom of the page that takes him to results 51-100, and so on
> >
> > In future versions, you might consider ranking the results based on some goodness-of-fit criterion based on the search string.
> Word stemming and language dependencies are some more goodies to add.
> > Richard Anderson, Ph.D.          www.unixscripts.com
> > Perl / Oracle / Unix                Richard.Anderson at raycosoft.com
> > Raycosoft, LLC                        Seattle, WA, USA
> > ----- Original Message -----
> > From: "John Cokos" <jcokos at iwebsys.com>
> > To: "Jonathan Gardner" <gardner at sounddomain.com>; <spug-list at pm.org>
> > Sent: Monday, March 12, 2001 8:06 PM
> > Subject: Re: SPUG: Segmentation Fault in mod_perl
> >
> >
> > > You're barking right up my tree here .... I do CGI
> > > work for a living, and work with mod_perl quite
> > > a bit.
> > >
> > > That being said, let  me ask you a few preliminary
> > > questions:
> > >
> > > 1.  The CGI Script that actually runs: is it mod_perl
> > >      compliant, in terms of exit status, "use strict" compatability,
> > >      etc?
> > >
> > > 2.  How do you have httpd.conf setup to accept mod_perl
> > >      programs?
> > >
> > > 3.  Sounds like you're going through a lot of machinations
> > >      to get XML output.  Seems to me that a "from scratch"
> > >      solution, or one that's designed from the outset to
> > >      work within the confines of mod_perl would be better
> > >      suited than to try and shoehorn in something else.
> > >
> > > Generally, coredumps from mod_perl are the result of
> > > "dirty" coding.  A few variables out of place, or a bad
> > > exit status can kill it pretty quickly.
> > >
> > > John
> > >
> > > ----- Original Message -----
> > > From: Jonathan Gardner <gardner at sounddomain.com>
> > > To: <spug-list at pm.org>
> > > Sent: Monday, March 12, 2001 4:16 PM
> > > Subject: SPUG: Segmentation Fault in mod_perl
> > >
> > >
> > > > Okay, run while you still can!
> > > >
> > > > We're running mod_perl on Apache. I am working on a module to
> > > > allow people to search our pages.
> > > >
> > > > I got ht://dig. This is a fine piece of software, and it works great. Ht://dig
> > > > has a program that works as a CGI script, and using the configuration files and
> > > > templates, you can configure almost anything you would like to.
> > > >
> > > > We want to really customize stuff, really really customize it. So I figured
> > > > we'd trick htdig to output XML, and use XML parser to parse it out, and then
> > > > take that and convert it into hashes and arrays and scalars we can use to fully
> > > > customize everything in Perl.
> > > >
> > > > Okay, so I wrote a module that takes the search parameters and returns a hash
> > > > with all the results stored inside. I wrote a test script that runs from the
> > > > command line and everything works beautifully. I am so happy I beam for joy!
> > > >
> > > > I plug it into Apache mod_perl and I get the dreaded segmentation fault. Not
> > > > just once, over and over again, almost every time I try to run it.
> > > >
> > > > The only hint I have is that perhaps it is an out-of-memory problem. This would
> > > > make sense. I have the program that consumes a lot of memory (the search), and
> > > > XML::Parser trying to pack everything into 'Tree' style. But it doesn't fail
> > > > during that - it fails when I start working on the tree with a couple of subs,
> > > > so if it WAS a memory problem shouldn't it fail during the XML parsing or
> > > > during the searching? How do I check to see how much memory the command-line
> > > > script uses?
> > > >
> > > > What do I do to find out the problem, short of putting a "warn"
> > > > between every line of code? How do I use the core dump - if it is useful at
> > > > all? What rotting nuggets of useful knowledge are lodged in the wisdom
> > > > teeth of the gurus, and could they use the toothbrush of the transfer of
> > > > knowledge to reveal those morsels to me? :-)
> > > >
> > > > --
> > > > Jonathan Gardner
> > > > gardner at sounddomain.com
> > > > (425)820-2244 x123
> > > >
> > > >
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