[Zope] Re: Zope 2.8 and conflict errors

[Tres Seaver]

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Maciej Wisniowski wrote:

>> That looks like a write conflict. MVCC helps to lower/eliminate the
>> rate of read conflicts. One option to reduce the rate of this 
>> writeconflict is to tune the session machinery to suit. For example
>> use session-resolution-seconds of say 300 seconds.
>
> Thanks!
> I've changed session-resolution-seconds and did some tests again.
> With DCOracle 2 there are still some errors (30 conflicts visible for users
> for 3000 requests), but with SQLRelay there are no errors at all! :)
> I didn't checked all 30 errors but I think these are all conflicts
> errors with Products.DCOracle2.DA.Procedure object like this one:
> 
> <P>An error was encountered while publishing this resource.
> </P>
> <P><STRONG>ZODB.POSException.ConflictError</STRONG></P>
>  Sorry, a site error occurred.<p><p>Traceback (innermost last):
> <ul>
> <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 427, in _commitResources</li>
> <li>  Module ZODB.Connection, line 637, in tpc_vote</li>
> <li>  Module ZEO.ClientStorage, line 893, in tpc_vote</li>
> <li>  Module ZEO.ClientStorage, line 877, in _check_serials</li>
> </ul>ConflictError: database conflict error (oid 0x0299de, class
>        Products.DCOracle2.DA.Procedure, serial this txn started
> with 0x035f181b76214155 2005-08-04 08:59:27.686696, serial
> currently committed 0x035f181b79752811 2005-08-04 08:59:28.466635)
> 
> Any ideas what can be done to remove this problem, except the obvious
>  solution - that is moving to SQLRelay ;) I tried _p_resolveConflict 
> function but without effect - it's used to resolve write conflict and
> I suppose these errors like the one above are read conflicts.

Nope;  any conflict propagated from within 'commit' is going to be a
write conflict;  more than one transaction is writing to the same
persistent object (in the ZODB) at the same time.

Tres.
- --
===================================================================
Tres Seaver          +1 202-558-7113          tseaver at palladion.com
Palladion Software   "Excellence by Design"    http://palladion.com
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