[imp] session problems & memcached

[Michael M Slusarz]

Quoting Kevin Konowalec <webadmin at ualberta.ca>:

> Horde: 3.1.2
> Imp: H3 (4.1.2)
> Turba: H3 (2.1.1)
> PHP Version: 4.4.1
>
> We've been getting complaints over the last few days of more and  
> more people being booted out of Imp frequently.  We haven't set any  
> sort of timeout in PHP or otherwise.  The only thing I can think of  
> that MIGHT be causing this if the memcached session keys are being  
> overwritten due to high volume.  I took a look and we're currently  
> allocating 512 MB to memcached.  We're getting almost 90,000 logins  
> per day.  Though I can't tell exactly what our concurrent load is  
> (though it'd be REALLY nice to be able to pull those kinds of stats  
> out of Imp) I'd be willing to bet it's hovering around 3000-4000  
> concurrent users at peak.
>
> Could the situation I described with the kickoffs be attributed to  
> load and memcached size?  If I added a second machine into the mix  
> running memcached would that seamlessly distribute the load?  What  
> would be a good memory size to allocate to memcached?

I'm not a memcached expert, but the scalability seems to be one of the  
main reasons to use it.  Thus, it wouldn't hurt to throw some more  
servers into the pool and see how it responds.

> Also I'm noticing THOUSANDS of zero-length session files in /tmp of  
> each horde front end.  Does Horde not clean up after itself?

This is not Horde's responsibility, it is PHP's.  See:
http://us2.php.net/manual/en/ref.session.php#ini.session.gc-probability
http://us2.php.net/manual/en/ref.session.php#ini.session.gc-divisor
http://us2.php.net/manual/en/ref.session.php#ini.session.gc-maxlifetime

michael

___________________________________
Michael Slusarz [slusarz at horde.org]