Posted by Marek Kilimajer on 01/17/05 16:54

N.Z. Bear wrote:
> Folks:
>
> I am experiencing a problem with httpd child processes suddenly
> exploding in memory size and consuming all available memory. The
> behavior is sudden, not gradual: within a few seconds or a minute the
> process swells to several orders of magnitude larger than its usual
> size.
>
> Listed below is a ps aux; the first httpd is a 'normal' one, the second
> is the problem child:
>
> nobody 23166 0.0 0.1 17572 2148 ? S 16:06 0:00
> /usr/local/apache/bin/httpd
> nobody 23167 1.4 63.7 2245624 1315584 ? D 16:06 1:00
> /usr/local/apache/bin/httpd
>
> Generally only a small number of child processes display this behavior:
> often just one at a time.
>
> The system setup is Linux with Apache 1.3.33, PHP 4.3.10 and MySQL
> 4.0.22-standard. I am not running mod_perl.
>
> The vast majority of traffic on the site is PHP scripts, some of which
> access the MySQL backend. I strongly suspect a problem in one of the
> scripts, but have not been able to identify specifically which one. I
> added the '%P' variable to my Apache log file and am now able to
> identify the specific requests that the Apache child process which
> explodes was handling prior to the error, but thus far no pattern has
> emerged (different scripts appear last each time). I suspect that the
> last entry I see in the log is the last successful request, not the one
> that causes the problem. (I am aware of log_forensic, which I learned
> would provide log output of a request *before* processing, but my skills
> are not sufficient to make me feel comfortable rebuilding my Apache
> server to include it at this time).
>
> I am working around the issue with a cron script that checks if a child
> process has exploded and then restarts Apache if needed; this helps to
> mask the issue but is obviously not a fix. I have set
> max_requests_per_child to a non-zero value but it has had no effect;
> based on my understanding this doesn't surprise me as this is not a
> gradual leak but a case where the process goes wild in the middle of a
> request).
>
> I recognize that it is unlikely that this problem can be
> diagnosed-at-a-distance, but would welcome suggestions on debugging
> tools and techniques which might help me narrow down the problem area.
> In particular: other than log_forensic, is there a way to truly see what
> that child process was doing when it went rogue? And does this behavior
> sound like that of a bad PHP script?
>
> Additional details & log files (including lsof, strace, and /proc
> output) can be found at this post on my blog:
> http://www.truthlaidbear.com/archives/2005/01/15/latest_on_performance_i
> ssues.php#001639
>
> Any and all suggestions are appreciated; thanks...

You can try to enable php memory limit.

You can also log http requests in php. Each request will create it's own
file in some log directory, log all necessary info, and then remove it
at the end of script run. This way the log directory should contain only
running and crashed processes.

HTH

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