[Project_owners] Can't access mozdev.org

Michael Dosser mic at strg.at
Tue Oct 19 09:46:01 PDT 2010


Hi Pete,

Am 07.10.2010 um 18:51 schrieb Pete Collins:

> Any ideas of the cause?


We use pecl-APC as our PHP opcode cache. On certain load spikes the internal locking mechanism from APC blocks all httpd/php processes (every httpd process hangs in lockf state). This results in timeouts for nginx which in turn displays 502 bad gateway.

I've tried running mozdev.org without APC but this slows down the project by 20-25% ... so this is not an option. I've evaluated XCache which has the same locking problem in a high load environment.

I've made some research and it turns out that most probably the problem is the default locking mechanism used by pecl-APC: it uses file locking. On one of our testing servers here at strg.at I have experimented with sysv semaphore locking on FreeBSD - this unfortunately is not very stable.
Linux_futex and pthread_mutex locks are not supported by the Ports system and therefore not available on FreeBSD.

pecl-APC provides also experimental spin locks. I have tested this option and it is very stable for now on our testing system (which does not have mozdev.org code installed). Today I have enabled spin locks on mozdev.org itself. It is now running since 40 minutes without any problems.

Mic

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