[ZODB-Dev] Wrong blob file being returned (similar to https://mail.zope.org/pipermail/zodb-dev/2011-February/014067.html )

[steve]

Hi,

I have a setup where 4 ZEO clients running on separate machines connect to a 
single DB server which runs on a different system by itself. The ZEO clients and 
the DB server all are at version ZODB3-3.10.2. Now, since the last few weeks 
some of our users have been reporting that they occasionally see incorrect 
images being returned.

On googling I came across the thread below and was wondering whether I am seeing 
the same thing as this:

https://mail.zope.org/pipermail/zodb-dev/2011-February/014067.htm

...although the setup and version is different (ie: ZODB-3.8 and RelStorage).

Unfortunately, sorry but I do not know enough about ZODB internals to be able to 
say for sure. Is there a way I can test whether the problem is indeed with the 
wrong blob file being returned from the blobcache ? FWIW, we haven't figured out 
a way to consistently reproduce this error ourselves. Other things that 
may/may-not be relevant:

a. our site is image heavy (36293 blob files) and the servers are behind a load 
balancer so in a single request to the web-app (a repoze.bfg site) we might even 
load collectively 20+ blobs from any of the 4 servers.

b. zeo connection string on the clients
zodb_uri = 
zeo://xxx.xxxx.xxx.xxx:8886/?blob_dir=%(here)s/../var/blobs&shared_blob_dir=false&connection_pool_size=50&cache_size=1024MB&drop_cache_rather_verify=true

c. $ cat var/blobs/.layout
zeocache

Any comments/suggestion on how to isolate and fix this problem would be appreciated.

cheers,
- steve

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