[Zope-dev] ZopePublication Competing writes/reads

[Hermann Himmelbauer]

Hi,
Just by chance, I pressed the reload button of my browser for quite some time, 
so that my Zope3-based site was reloaded over and over. I was surprised to 
find the following in the logs:

2008-10-20T18:45:15 WARNING ZopePublication Competing writes/reads 
at /BSPSite/act/s/info: database conflict error (oid 0x0733, class 
zope.session.session.SessionData)

Can someone explain me why this happens, if this is something dangerous or if 
I can forget about it?

I tested the site with Apache Bench (ab2), with many concurrent requests and 
could not reproduce the problem.

So my wild guess is the following: 
I use session.PersistentSessionDataContainer for my session, so every request 
will probably read/write to some Zope3 container/btree. And then, for some 
reasons these reads/writes compete, which leads to the above warning. If I 
use AB2, there's no cookie, thus no session, hence the problem does not 
arise.

On the other hand, the zope root site (the Rotterdam ZMI) seems not to have 
this problem, as it seems, I can't trigger this warning message with fast 
reloads.

I'm unsure if I should just ignore that or do something about it.

Any hints?

Best Regards,
Hermann

-- 
hermann at qwer.tk
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