[ZODB-Dev] ZODB.POSException.ReadConflictError

[root]

Hi Dieter,

thanks for your response.

> Dr. Thomas Wagner wrote at 2003-12-17 11:48 +0100:
> 
>>...
>>we are running a portal with 10000 users, using Plone, Zope 2.7b3, ZEO 
>>and 4 ZEO Clients, all more than generously equiped. Since upgrading to 
>>2.7b3 we get a frequent ZODB.POSException.ReadConflictError for various 
>>objects togehter with Uuser authentication (log in oder access via 
>>memberdata_tool. The error only occurs on the ZEO clients and is then 
>>responded to all requests.
>>
>>We checked for some unfortunate code in our skripts like discussed in 
>>this list some days ago but that didnt bring up any strange constructions.
>>
>>does anyone have the same problem or can you give us some idea how we 
>>can find out more about this error?
> 
> 
> You have several options:
> 
>   *  "ReadConflictError" only occurs if someone else writes the
>      object. Analyse which object is affected and determine
>      whether it is right that it is written

it seems that alle member objects are affected.

> 
>   *  I have a ZODB 3.1 patch that avoids "ReadConflictError"
>      by implementing snapshot delivery: object state is delivered
>      as it has been when the transaction started.
> 
>      Note that this patch can lead to ZODB inconsistencies under
>      special circumstances (one of the ZEO tests fails on
>      high speed computers).

Hmm, any inconsistency seems too dangerous to risk.
> 
>        <http://www.dieter.handshake.de/pyprojects/zope>
> 
>   *  Jeremy has designed an MVCC (MultiVersion Concurrency Control)
>      protocol that is similar to the above patch but does
>      not suffer the inconsistency problem above. It is destined for
>      ZODB 3.3. Based on experience, I expect ZODB 3.3 to
>      be released somewhere near mid 2004.
> 
this is much to late :-(

>   *  I will backport some of Jeremy's MVCC proposal for ZODB 3,2
>      within the next two weeks. The patch will be available
>      at my Zope page (see above).
> 

This is really good news!! We are running a large scale portal an have 
thousends of users waiting for a solution!

I will keep you informed.

Thanks
Thomas