Here is the story: I use Lighty 1.4.19 with fcgi & php. About once a day all I can get is 501 service unavailable, for which I have failed to track a reason for. Simply at some point no new requests are passed to php-cgi processes, which remain idle and the request queue builds up until they are marked as overloaded. First guess: server overload, but no - when it happens cpu load is below 50% and there are no excessive io operations. Once 501 starts appearing it drops to < 10% and all php-cgi processes are exactly at 0. Second: server load spike due to cron job, or something similar, causes fcgi processes to marked as dead. No dice - no time pattern, I have even disabled all cron jobs to check it. Third: php-cgi processes just die due to some fcgi bug. Nope. restarting lighty does not solve that, even if I make sure all php-cgi processes are killed with it - killall -9 php-cgi. If I restart just Lighty + fcgi + any other web related services (like mysql) nothing changes - to make a difference I have to reboot.. To make it even more bizarre it sometimes fixes itself without any intervention - it just starts working after a couple of minutes. Or not. It's random. Oh, and the very same configuration (including php executed) has worked just fine for last couple of months. Any idea what else I could be looking for? I am pretty much done with the normal stuff and I am ready to test borderline impossible reasons should they lead to a solution.
on 15.07.2008 23:34
