1. Using ulimit to limit resource usage by Apache.
We're running a web server, hosting several hundred virtualhosts, most of
whom use PHP. Since there is so much use of PHP, I've compiled it into
Apache, rather than as a loadable module.
Rather frequently, it seems that a httpd process (we've tracked it
happening) will go rogue and consume all memory on the server (1 gig RAM, 2
gigs swap) which brings the server to its knees and make it utterly
unresponsive. Since it's co-located, it's an utter pain to have to go in
and manually reboot the machine.
In /etc/profile, I added "ulimit -v 250000", intending that any process
should have no more than a rather generous 250 MB of memory available to
it, intending the prevention of a rogue httpd process from devouring all
the resources. But it seems that the machine was knocked over again this
evening, shortly after a reboot (remotely) to test httpd.
I was wondering if putting the "ulimit -v" command in /etc/profile was
appropriate for a daemon process. Ulimit is an internal bash command and
daemons don't necessarily run from the shell. The httpd server is run
from the initscript, which is a shell script; this script will have the
ulimit constraints imposed upon it and, I presume, so will the parent httpd
process started from this script.
But what about the child servers launched by the parent httpd process? I
would presume that the shell isn't involved in their invocation by the
parent httpd process. Will they inherit the same ulimit constraints that
applied to the original shell script?
Also, from what I understand, the default action of ulimit is to impose
soft limits. Would "ulimit -Hv 250000" in /etc/profile better prevent a
rogue process incapacitating the machine?
Does anyone have a suggestion how I might better handle this situation?
Is there a method within Apache itself for constraining the system resource
usage by any virtual host or child server?
--
Cheers,
Rob
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