It might. ZEO adds network overhead to ZODB transactions,
which generally increases the likelihood of conflict errors.


I've created ZEO and executed the same test with my application.

Tests were done with SQLRelay backend (DCOracle2 is running now ;))

I have tested this with 50, 55, 60 and 70 users.
with 50 users: no 'HTTP/1.1 500' errors
with 55 users: no 'HTTP/1.1 500' errors
with 60 users: no 'HTTP/1.1 500' 1 error for 1800 urls requested
with 65 users: no 'HTTP/1.1 500' 4 errors for 1950 urls requested

All errors are with OOBTree and as I can see with tempstorage.TemporaryStorage. They look like:

<li>  Module ZPublisher.Publish, line 187, in publish_module_standard</li>
<li>  Module ZPublisher.Publish, line 161, in publish</li>
<li>  Module ZPublisher.Publish, line 161, in publish</li>
<li>  Module ZPublisher.Publish, line 161, in publish</li>
<li>  Module ZPublisher.Publish, line 151, in publish</li>
<li>  Module Zope2.App.startup, line 158, in zpublisher_exception_hook</li>
<li>  Module ZPublisher.Publish, line 119, in publish</li>
<li>  Module Zope2.App.startup, line 215, in commit</li>
<li>  Module transaction._manager, line 84, in commit</li>
<li>  Module transaction._transaction, line 381, in commit</li>
<li>  Module transaction._transaction, line 379, in commit</li>
<li>  Module transaction._transaction, line 424, in _commitResources</li>
<li>  Module ZODB.Connection, line 462, in commit</li>
<li>  Module ZODB.Connection, line 503, in _commit</li>
<li>  Module ZODB.Connection, line 526, in _store_objects</li>
<li>  Module tempstorage.TemporaryStorage, line 200, in store</li>
</ul>ConflictError: database conflict error (oid 0x0944, class BTrees._OOBTree.OOBTree, serial this txn started with 0x035f134dc11a2977 2005-08-03 12:29:45.258327, serial currently committed 0x035f1357051c7199 2005-08-03 12:39:01.197916)


So far I see that DCOracle2 version of my app caused 9 errors for the same scenario with 50 users. These are conflict errors with DCOracle2.DA.Procedure and in ZEO.ClientStorage...

--
Maciej Wisniowski

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