[ZODB-Dev] My turn for ReadConflictErrors...

[Toby Dickenson]

On Thursday 12 June 2003 11:57, Wankyu Choi wrote:

> Conflicts happen even with
> stock CMF/Plone types (Documents) with no such write-intensive properties.
> I suspect my ZEO setup... but don't know where to look since I can't figure
> out what's writing what. There should be no thread writing anythning, only
> threads reading something, in which case no conflict (isn't
> READconflicterror a misnomer?) should be raised. But I still see these
> conflicts. Out of suspects or ideas.

Go to Zopes root folder and click on 'undo'. It will show you the urls that 
triggered every recent write transaction. 

If the undo log shows no trace after you reproduce a conflict error then you 
may have a zodb or storage bug. But I think that is unlikely.

If you cant figure out why those urls are causing a write transaction then 
using DirectoryStorage's dumpdsf tool may help. See the second and third 
examples at http://dirstorage.sourceforge.net/dumpdsf.html - the second is a 
dump of a transaction file and shows what objects were modified at that time. 
The third shows a dump of one of those objects.

> I even tried Dieter's "no more readconlfict" patch. No use.

His FileStorage patch is great if you are using FileStorage, but of little 
help to DirectoryStorage users. Porting the technique is somewhere on my todo 
list.

> Why the conflicts? I wasn't writing anything. 

Im sure your application is writing - even if you dont expect it to.

> Any storage system would have a conflcit resolution mechanism. I've been
> using MySQL for years, for example, and it didn't give me any such
> headaches about read/write conflicts. Why can't ZODB be like that in terms
> of resolving conflicts? ( this might be another stupid newbie question...
> but at least it looks like a legitimate one ;)

Im sure you just have a dumb bug that is causing too many writes when you 
expect there to be zero writes.

-- 
Toby Dickenson
http://www.geminidataloggers.com/people/tdickenson