[Zope] large installations and conflict errors

[Andrew Langmead]

On Aug 9, 2005, at 7:01 AM, Sascha Ottolski wrote:

> What we've seen so far: we used to set the cache-size to 250 MB;  
> and every
> know and than we have to observe that after a restart of a client a  
> cache
> verification is necessary (while not always obvious, why this  
> happened),
> which often takes "forever" (that is, 10 to 20 minutes are  
> possible). And
> that during such a verification, the whole system seems to be down  
> (in the
> sense that delivery of pages is slow as hell :-(). I think that in  
> such a
> case simply deleting the cache file and starting with a fresh one  
> is way
> faster, but have no hard numbers to prove that feeling.

In Zope 2.6, we wound up turning off persistent cache files. Having  
things be a little bit slow on one client while the cache filled up  
was preferable to the systemwide torture the re-verification of a  
cache file. Zope 2.7 and higher have a shortcut to cache  
verification, which can be adjusted with the "invalidation-queue- 
size" parameter.

Unfortunately, there are times where the ZEO client will decide to do  
a re-verification of a transient cache file (I think due to  
unexpected runtime exceptions) The best we've found to do is to  
monitor the health of the clients and the servers and when they all  
get simultaneously busy, find the client re-verifying and restart it.