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In top I keep seeing zombie processes (not more than one at a time), they disappear quickly (within 10 seconds), but a new zombie pops up a few seconds later. My server runs 3 sites, 2 written in PHP, one in Perl, all served by Apache . For the PHP sites I use mod_rewrite to create nice looking URLs. I having been trying to figure out which page or script causes these zombies, but can't find it. Is there a way to connect the PID of a process to the request it was executing? To find out what causes the zombies I stopped the Perl site and one of the PHP sites, nothing changed, the zombies keep coming, so my best guess is that I have narrowed it down to one site, but then again, maybe it has nothing to do with a particular site I (I can't take the remaining site offline to check, since people are working with it). I am running Debian on that server, this is the config:

Apache/2.2.9 (Debian) DAV/2 SVN/1.5.1 PHP/5.2.6-1+lenny8 with Suhosin-Patch mod_ssl/2.2.9 OpenSSL/0.9.8g mod_perl/2.0.4 Perl/v5.10.0

Any help or pointing me in the right direction is greatly appreciated, I have been googling and trying things for days now (I learned a lot from it though ;-) ).

During the quiet Christmas holidays I had the opportunity to take the 3rd site offline for a couple of minutes. To my surprise I kept seeing zombies popping up, so it seems it has nothing to do with one site in particular but rather with some setting in Apache. Any ideas anyone?

user525870
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  • it may very well be something different. for example not found but configured apache modules cause zombies. however since the lack of good inter process communication in threaded php programming, its often a praxis to deliberately produce zombies that commit suicide after certain jobs. – The Surrican Dec 23 '10 at 17:02
  • Thanks for the suggestions! The modules that I use are all included with IfModule so that can't be it. The sites do not use multithreading so that is ruled out as a possible cause as well. Any other thoughts? I think it would help to know what the apache process was doing on the moment that it becomes a zombie, is there a way to get that information (I searched the log files but could not find anything) – user525870 Dec 24 '10 at 11:22

2 Answers2

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I just answered a very similar question

Apache spawning zombie processes when php is called

the short answer is it's normal.

Community
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David Chan
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By enabling mod_status you'lle get some more details in the /status url of your server, and even the details of the last page served if you set the ExtendedStatus directive to "On". But you should not use that setting for a to long time in a production server.

Then I would like to know how do you know it's a zombie process? Are you sure it's not the 'normal' subprocess of apache, serving the client requests? How many subprocess do you have for your apache?

regilero
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