david at dbooth
Jan 8, 2012, 6:02 AM
Post #3 of 3
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Re: [SOLVED] Re: How to run shell command from response handler? (Apache2 child segmentation fault)
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Hi Jon,
My code actually needed to run other shell commands. I just used the
`date` function as a simple example to demonstrate the problem.
David
On Sat, 2012-01-07 at 02:44 -0700, Jon wrote:
> Hello All,
>
>
> Ok, maybe I'm missing the whole point of this thread, but why is this
> solution better than using the built-in perl `date` function?
>
>
> Personally, I think using the system 'date' function provides too many
> variables [read: problems] when attempting cross-platform continuity.
>
>
>
> Maybe I have misunderstood the whole point of this thread, but it
> seems to me that everyone is over-engineering the problem... (i've
> only been a Perl programmer for like three years, so I still have
> ton's to learn... hopefully I can learn from this if I'm way off
> base)
>
>
> Thanks,
> Jon A
>
> On Tue, Jan 3, 2012 at 8:38 PM, David Booth <david [at] dbooth> wrote:
> Thanks for the suggestion. I tried it with prefork and the
> problem
> still occurred. HOWEVER, I then decided to remove all modules
> down to a
> minimal example, and discovered that the mere inclusion of the
> following
> module:
>
> use Test::MockObject;
>
> was causing the segmentation fault after several successful
> requests,
> even though no functions whatsoever were called. Since this
> appears to
> be a bug in Test::MockObject, I reported the bug here:
> https://rt.cpan.org/Public/Bug/Display.html?id=73723
>
> The bug report shows the exact minimal handler code that I
> used to
> reproduce the bug.
>
> Best wishes,
> David
>
>
> On Tue, 2012-01-03 at 17:26 -0500, Daniel Risacher wrote:
> > I think I've been bitten by this too, years ago.
> >
> > I *think* I solved it by switching to mpm_prefork, which was
> > unsatisfying, but adequate for my needs.
> >
> > On Tue, Jan 3, 2012 at 5:21 PM, David Booth
> <david [at] dbooth> wrote:
> > > I tried redirecting stderr to /dev/null and it did not
> help:
> > > system("date >> $f 2> /dev/null");
> > >
> > > I am using the worker processing model. Does it work for
> you (or anyone
> > > else) without causing periodic child process segmentation
> faults?
> > >
> > >
> > > On Tue, 2012-01-03 at 16:29 -0500, Daniel Risacher wrote:
> > >> It's been a while since I looked at doing this, but IIRC
> it's fairly
> > >> dependent on the processing model that Apache is using.
> Are you
> > >> mpm_prefork, or mpm_worker?
> > >>
> > >> Also, I found it was important to redirect stderr
> to /dev/null:
> > >>
> > >> sub play {
> > >> system "/usr/bin/xmms -t 2> /dev/null";
> > >> }
> > >>
> > >>
> > >> On Tue, Jan 3, 2012 at 12:48 PM, David Booth
> <david [at] dbooth> wrote:
> > >> > I am trying to run a shell command from a mod_perl2
> response handler.
> > >> > It works properly for some number of HTTP requests, but
> sometimes it
> > >> > fails (somewhat randomly) and I see in my Apache2 error
> log that one of
> > >> > the Apache2 child processes has died with a
> segmentation fault.
> > >> > For example, /var/log/apache2/error.log shows:
> > >> >
> > >> > [Tue Jan 03 12:16:10 2012] [notice] child pid 3538 exit
> signal Segmentation fault (11)
> > >> >
> > >> > Is this normal? How does one normally run a shell
> command from a
> > >> > response handler? I do not want to return the
> command's output to the
> > >> > client.
> > >> >
> > >> > Here is a trivial example response handler that
> exhibits this behavior:
> > >> >
> > >> > sub handler
> > >> > {
> > >> > my $r = shift || die;
> > >> > my $f = $ENV{DOCUMENT_ROOT} . "/date.txt";
> > >> > system("date >> $f");
> > >> > $r->internal_redirect("/date.txt");
> > >> > return Apache2::Const::OK;
> > >> > }
> > >> >
> > >> > Can anyone provide any guidance? Does this work for
> you?
> > >> >
> > >> > Note that you may not notice the problem if you don't
> carefully watch
> > >> > the Apache2 error log (e.g., with "tail
> -f /var/log/apache2/error.log"),
> > >> > because Apache2 automatically spawns new children
> processes as needed,
> > >> > and client (such as Firefox or wget, though not curl)
> seem to
> > >> > automatically re-try the request when it fails, thus
> giving the illusion
> > >> > of succeeding.
> > >> >
> > >> > P.S. I have posted about this on perlmonks, but thus
> far have not found
> > >> > a solution:
> > >> > http://www.perlmonks.org/?node_id=945947
> > >> >
> > >> >
> > >> > --
> > >> > David Booth, Ph.D.
> > >> > http://dbooth.org/
> > >> >
> > >> > Opinions expressed herein are those of the author and
> do not necessarily
> > >> > reflect those of his employer.
> > >> >
> > >>
> > >>
> > >
> > > --
> > > David Booth, Ph.D.
> > > http://dbooth.org/
> > >
> > > Opinions expressed herein are those of the author and do
> not necessarily
> > > reflect those of his employer.
> > >
> >
> >
>
> --
> David Booth, Ph.D.
> http://dbooth.org/
>
> Opinions expressed herein are those of the author and do not
> necessarily
> reflect those of his employer.
>
>
>
>
>
>
> --
> Best Regards,
> Jonathan David
>
>
> Please excuse any brevity or typos as this e-mail is most likely sent
> from a mobile device.
>
>
--
David Booth, Ph.D.
http://dbooth.org/
Opinions expressed herein are those of the author and do not necessarily
reflect those of his employer.
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