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From Douglas Duckworth <dod2...@med.cornell.edu>
Subject Re: [users@httpd] Apache 2.4 DoS?
Date Tue, 14 Nov 2017 19:18:29 GMT
Thank you Rainer Canavan!

Will try using gdb to get more information!

Thanks,

Douglas Duckworth, MSc, LFCS
HPC System Administrator
Scientific Computing Unit
Physiology and Biophysics
Weill Cornell Medicine
E: doug@med.cornell.edu
O: 212-746-6305
F: 212-746-8690

On Mon, Nov 13, 2017 at 7:04 AM, Rainer Canavan <rainer.canavan@sevenval.com
> wrote:

> On Fri, Nov 10, 2017 at 6:41 PM, Douglas Duckworth
> <dod2014@med.cornell.edu> wrote:
> > Hi
> >
> > I am running old PHP under Apache httpd-2.4.
>
> [...]
> > Though, ever few weeks, we see sudden increase in workers who never seem
> to
> > retire:
> >
> > [Fri Nov 10 02:43:20.019924 2017] [mpm_prefork:error] [pid 13584]
> AH00161:
> > server reached MaxRequestWorkers setting, consider raising the
> > MaxRequestWorkers setting
> >
> > user@server[/var/www]$ ps aux | grep [h]ttpd | wc -l
> > 257
>
> If the php locks up while processing your request, no logs will be
> written. You may be running
> into a bug where circular, unresolvable dependencies for a lock
> prevent the processes from
> completing their requests. To check what's going on, install gdb, the
> debug info for your php
> and httpd and find the .gdbinfo that came with the httpd and php
> version you're using. Then
> attach gdb to any of the hanging processes (gdb `which httpd` PID),
> source both .gdbinit files,
> do a "zbacktrace" and a "bt full", and repeat for some other hanging
> processes. Depending
> on the type of lock,  you may be able to identify the first process
> that has acquired that lock
> that all others are waiting for, and the php code and / or php module
> that causes it.
>
> rainer
>
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