Cryptic Apache Error

Each night our webmail servers automatically restart httpd to clean up memory and start fresh. Last night one of our servers hit this error upon restart:

[crit] (28)No space left on device: mod_rewrite: could not create rewrite_log_lock Configuration Failed

I had never seen this error before and had no idea what it meant, but Google helped me out:

http://www.goldfisch.at/knowledge/224

After some testing, I found that Apache leaks a couple of semaphores after each restart and eventually w/o a server reboot will run out of resources. So I changed our restart script to clean up these semaphores each night.

ipcs -s grep nobody perl -e 'while () { @a=split(/\s+/); print `ipcrm sem $a[1]`}'

In case you are wondering, it's not a big deal if a webmail server doesn't restart properly. Our load balancers quickly take a down server out of rotation so that customers are not affected. Thank you keepalived.