[Server-devel] Ejabberd CPU/RAM Spike -> Crashes

[Martin Langhoff]

On Mon, Dec 21, 2009 at 4:18 PM, crodas <crodas at paraguayeduca.org> wrote:
> According to the ticket the solution is a locking file which prevent the
> re-execution. Well, I've wrote a dumb script awhile ago that might help,
> it's not innovating, but it might help:

Thanks! The lock I coded is using a moodle-specific bit of code, so
it's in PHP, using moodle internal calls, and it uses PostgreSQL's
atomicity to achieve it in a non-racey way.

This has the advantage of locking a smaller bit of code -- not the
whole 'cron' run.

BTW, the lock script you're using is a bit racey (things could
definitely happen after the if [ -f $LOCK ]). If you want to do this
safely in shell scripting, using dotlockfile which is widely
available, even in oldish Linuxes. Recent Linuxes all include
/usr/bin/flock which is also sanely atomic, so that's what we use on
the XS for this task...

cheers,



m
-- 
 martin.langhoff at gmail.com
 martin at laptop.org -- School Server Architect
 - ask interesting questions
 - don't get distracted with shiny stuff  - working code first
 - http://wiki.laptop.org/go/User:Martinlanghoff