[silva-dev] ZODB.Conflict errors when having lots of documents in a folder

[Nico Grubert]

> We typically see such conflict errors. While they're perturbing, as
> yet we don't have any reports of actual damage (to content or
> functioning) being done.
> 
> We're hoping that with the advent of Zope 2.9 and MVCC
> (MultiVersionConcurrencyControl) these errors will cease making
> sysadmins nervous.

Hi Kit,

just a short note:

Since I read the text

   ZODB 3.4 with MVCC (multi version concurrency control) support. MVCC
   solves nearly every problem with ZODB read-conflict errors which is
   very important for high-traffic Zope sites.

on the Zope 2.8.8 release page I have tried Silva 1.5.6 with Zope 2.8.8. 
But I still get the same ZODB conflict errors.

Maybe useful for your Silva core developers:
Since I really wanted to know exactly which object causes the ZODB 
conflicts, I inspected the ZODB via "ZODB.utils.p64".

One error message in /log/event.log reads:
The corresponding error message in /log/event.log reads:
2006-08-07T11:46:25 INFO ZODB.Conflict database conflict error (oid 
0x2c, class BTrees._OOBTree.OOBTree, serial this txn started with 
0x036755a94d2334bb 2006-08-07 09:45:18.079107, serial currently 
committed 0x036755aa3a3312bb 2006-08-07 09:46:13.640509) at 
/silva156/edit/tab_status (1 conflicts, of which 0 were unresolved, 
since startup at Mon Aug  7 11:36:03 2006)

 From that error message I took the oid 0x2c in order to inspect the 
ZODB like this:

# fetch object from ZODB by a given address (e.g. 0x2c)
from Zope import app
from ZODB.utils import p64
root = app()
obj = root._p_jar[p64(0x2c)]
print obj

This returns:

   <HelpSys.APIHelpTopic.MethodDoc object at 0x41491e2c>


I took some other oids from the ZODB.Conflict errors to see what kind of 
objects cause the ZODB conflict errors. Here are some further examples:
	<Product at Annotations>
	<BTrees._OIBTree.OIBTree object at 0x4385c2fc>
	<KeywordIndex at permissions>
	<BrowserIdManager at browser_id_manager>
	<BTrees.Length.Length object at 0x42d5876c>


Regards,
    Nico