[ZODB-Dev] conflict errors in persistent ZEO client cache

[Jeff Shell]

In ZODB 3.8.0, while prepping a customer's site to go from staging to  
production and doing a fair amount of big operations, we started  
seeing conflict errors. It was a 200MB cache size, with a persistent  
client cache. Keeping the same cache size (against a base storage of  
about 700MB) but turning off the persistent client cache seemed to  
make the problem go away.

The persistent cache file at the time of the conflict error was close  
to 200MB in size, but doesn't it always go to the size configured,  
regardless of how much data is inside?

Anyways, I saw this in the ZODB 3.8.1 beta release notes:
> - When using ZEO Client Storages, Errors occured when trying to  
> store objects too big to fit in the ZEO cache file.

Out of curiosity, what Errors were occurring? I don't think we were  
trying to store individual objects too big to fit in the ZODB, but the  
transactions were likely touching a lot of objects.

I'm trying to figure out if I had a configuration problem, software  
problem, or both.

Thanks,

Jeff Shell
jeff at bottlerocket.net