Hermann Himmelbauer wrote:
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.
Presumably that site does not use sessioning so does not suffer from the same problem. Laurence