[Zope] strange database read conflict error

[Peter Bengtsson]

2009/8/28 Dragos Chirila <objectvalues at gmail.com>:
> Peter,
>
> Than you for your response. Please find below a few things:
>
> - I give up using sessions in the website's front and years ago :)
> There is only one page left that is using them, when u subscribe to
> our newsletter but I don't think that this affects because is used
> rarely
>
It might be used anyway. It'll be empty (except the
subscribe-to-newsletter page) all the time but it might still be in
use.
I think there is always a REQUEST.SESSION object.

> - I am using Yahoo Maps Ajax API to display maps; also some ajax calls
> for our build in chat (only for logged users)
That's unrelated. Yahoo! isn't using ZODB.

>
> So if the things above are causing read conflicts why only for this
> particular object? There is nothing special or different with this
> one...
>
It could be some other piece of code that tries to read from ZODB more
than once and whatever it's trying to read might be something slow
(slow for a computer).

Have you tried running ZopeProfiler on your site to figure out if
there are certain (ZO)DB related functions that are called either many
many times or few but slow times.

> Thanks again,
> Dragos
>
> On Fri, Aug 28, 2009 at 12:19 PM, Peter Bengtsson<peterbe at gmail.com> wrote:
>> The fact that the class is Products.Transience.Transience.Increaser
>> makes me suspect that you're using sessions and within the same
>> session you make too many read requests to the ZODB. When the load is
>> too high, after a certain amount of attempts Zope will say, "piss off!
>> ...for a while and come back later". So it comes back later and works
>> fine.
>> Are you using lots of AJAX requests? That can sometimes cause read
>> conflict errors.
>>
>> 2009/8/28 Dragos Chirila <objectvalues at gmail.com>:
>>> Hello everyone,
>>>
>>> I have a question regarding a database read conflict error. I would
>>> appreciate any thoughts on this issue.
>>>
>>> I am using Zope 2.8.9.1-final, Python 2.3.7 with a ZEO server and 4
>>> clients for 6 months now. I have noticed that the event.log is filled
>>> with read conflict errors like the one below:
>>>
>>> 2009-08-28T10:29:26 INFO ZODB.Conflict database read conflict error
>>> (oid 0x09, class Products.Transience.Transience.Increaser) at
>>> /VirtualHostBase/http/metropotam.ro:80/metropotam/VirtualHostRoot/Opera/loc4769172835-Ateneul-Roman/
>>> (21 conflicts, of which 0 were unresolved, since startup at Thu Aug 27
>>> 15:25:02 2009)
>>>
>>> This URL of the object is
>>> http://metropotam.ro/Opera/loc4769172835-Ateneul-Roman . We have
>>> around 2000 objects of the same type and this is *the only one* that
>>> generates read conflict errors.
>>>
>>> I have tried a few things:
>>>
>>> 1.      Edit object and recatalog it
>>> 2.      Rename it
>>> 3.      Delete object, pack database, create a new object and then rename
>>> it to keep the URL alive
>>> 4.      checked the data.fs and got no errors (fstest.py)
>>>
>>> None of the above solved the problem; I still get a lot of conflicts.
>>>
>>> Is there a way to fix this? I found it very strange that I get
>>> conflicts only for this object and for no other of the same type, even
>>> in the same folder...
>>>
>>> Thank you,
>>> Dragos Chirila
>>> _______________________________________________
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>>
>>
>>
>> --
>> Peter Bengtsson,
>> work www.fry-it.com
>> home www.peterbe.com
>> hobby www.issuetrackerproduct.com
>> fun crosstips.org
>>
>
>
>
> --
> Dragos Chirila
> objectValues at gmail.com
> (+4) 0722 395375
> _______________________________________________
> Zope maillist  -  Zope at zope.org
> https://mail.zope.org/mailman/listinfo/zope
> **   No cross posts or HTML encoding!  **
> (Related lists -
>  https://mail.zope.org/mailman/listinfo/zope-announce
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>



-- 
Peter Bengtsson,
work www.fry-it.com
home www.peterbe.com
hobby www.issuetrackerproduct.com
fun crosstips.org