[ZODB-Dev] ZEO 2 : cache twiddling

[Shane Hathaway]

Guido van Rossum wrote:
>>>The first time I do something that involves reading from one of the 
>>>mounted storages, I have to wait an _age_. What's happening? Is the 
>>>ClientCache filling itself with all objects it can before it does 
>>>anything? Certainly much slower than before.
>>
>>Uh-oh.  I wonder if you're accidentally sharing one cache between three 
>>storages.  This is bound to break very badly, and there's currently 
>>nothing that detects this condition.  Could you "ls -l" the directory 
>>where your cache files are?  It's usually the same directory that holds 
>>Data.fs.
> 
> 
> How could this happen?  Persistent caches have different names based
> on the storage name and client name.  Non-persistent caches use
> tempfile.

Chris is running three storages in the same process.  The client name is 
the same since it comes from the ZEO_CLIENT environment variable, and 
the storage name for all three is probably the default, "1".  But if 
Chris is running with non-persistent caches then you're right, there's 
no issue.  Chris?

>>Of course, I would expect ZODB to shatter in a million pieces if
>>this were the case, rather than chug along with some occasional
>>breakage.  Hmph.
> 
> 
> Not if the oid sets are distinct (dunno if they are).

Ah-ha, that makes sense then.  The OID sets are likely to intersect 
randomly.  This would result in gradual chaos.

Shane