[ZODB-Dev] Location of transient caches

[Jim Fulton]

On Fri, Feb 19, 2010 at 12:38 PM, Andy Theyers <andy.theyers at isotoma.com> wrote:
> Hi there
>
> Thanks for the speedy responses!
>
>> How big is your database?  How are you talking to the ZEO server?
>> TCP or unix domain sockets. Given that they're on the same machine,
>> I'd recommend the later, in which case, you may not get that much benefit
>> from the caches. You might try using smaller caches.
>
> The database is 600MB (packed).
>
> I realised I needed larger than the default 20MB from reading
> http://wiki.zope.org/zope2/ZEOCache, and I got the 300MB from the ZEO
> setup section of this document on Plone.org  - http://is.gd/8Jl48
> Nothing more scientific than that, I'm afraid!
>
> I wondered if we would be getting much from the caches.  If I moved to
> sockets could I reduce the cache size right back down to the default?

As long as you are on the same machine, you should use unix-domain
sockets.

I would would make some performance measurements as you
adjust the cache to decide what cache size to use.  I'm pretty sure you
can get away with reducing your cache size quite a bit.

>
>>> While under this configuration the site failed due to cache corruption.
>>>  This caused us to remove the persistent cache option, again as
>>> recommended in various mailing list posts.
>>
>> Note that the latest versions of ZODB (3.8 and 3.9) have fixed
>> most or all (not quite sure :) of the cache corruption issues.
>
> We're Plone 2.5, Zope 2.9, ZODB 3.6.  I've not tried upgrading, and
> wouldn't want to unless it was a) easy and b) guaranteed to fix
> something that was properly broken.

I can't say how easy it would be to upgrade. Upgrading to
at least 3.8 would almost certainly address the persistent cache
issues you're having.  Given how tiny your database is, :), I doubt
having a persistent cache is worth the bother.

Jim

-- 
Jim Fulton