[ZODB-Dev] Location of transient caches

[Andy Theyers]

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?

>> 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.

> ZEO uses the tempfile module for transient caches, which
> honors several environment variables to control where
> temporary files go. You can also control this by setting a tempfile
> module attribute from Python. See the tempfile documentation.

Perfect, thank you!

> (I'd be happy to accept a patch/checkin with test to make this
>  configurable from the ZEO configuration.)

Having spent my day trying and failing to work out how it worked I may 
not be the person for the task!

I'll see how I get on

Thank you again for your help

Cheers

Andy
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