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From Damien Katz <dam...@apache.org>
Subject Re: An asynchronous write bug in CouchDB 0.9?
Date Mon, 27 Apr 2009 19:14:23 GMT
This is now fixed in trunk.

-Damien

On Apr 27, 2009, at 1:49 PM, Steven Hazel wrote:

> Okay, I think I've confirmed this theory.  Thanks to your guidance I  
> managed
> to create a python script that can reproduce the problem on my  
> macbook:
> http://saucelabs.com/couch-bug.py
>
> (To run it, you need the latest trunk version of couchdb-python.)
>
> Looking at our logs, we started seeing this problem just after we  
> crossed
> the threshold to >100 dbs.  And very frequent reads to the problematic
> database fixed the issue, because they made it always more recently  
> active
> than most of the others.
>
> - Steve
>
> On Mon, Apr 27, 2009 at 9:40 AM, Steven Hazel <sah@saucelabs.com>  
> wrote:
>
>> I think we do have a lot of active databases -- we have a view that  
>> is run
>> frequently against each of our 137 databases.
>>
>> - Steve
>>
>>
>> On Mon, Apr 27, 2009 at 6:20 AM, Damien Katz <damien@apache.org>  
>> wrote:
>>
>>> It looks like the db server instance is being restarted before it  
>>> commits
>>> the header, but it's odd you aren't seeing any errors on the  
>>> console. If
>>> it's a crash it should dump an error to the console.
>>>
>>> One thing that occurs to me, do you have a lot of active databases  
>>> (> 100)
>>> ? I think it's possible when you hit the max dbs open, CouchDB  
>>> will shutdown
>>> an idle instance with pending deferred commit, which is a bug.
>>>
>>> -Damien
>>>
>>>
>>>
>>> On Apr 27, 2009, at 12:52 AM, Steven Hazel wrote:
>>>
>>> Hi,
>>>>
>>>> Last week we discovered that records in one of our CouchDB  
>>>> databases were
>>>> occasionally being reverted to the previous revision. We believe  
>>>> this is
>>>> due
>>>> to a bug in CouchDB 0.9 related to asynchronous writes.  Turning  
>>>> off
>>>> asynchronous writes with the X-Couch-Full-Commit header fixes the  
>>>> problem
>>>> for us.  I've written up the problem in more detail here:
>>>> http://saucelabs.com/couch-bug.html
>>>>
>>>> We haven't yet reproduced this problem outside our production
>>>> environment,
>>>> but can trigger it there on-demand.  Although we have a work- 
>>>> around that
>>>> solves the immediate problem for us, we're happy to help out in  
>>>> tracking
>>>> down the underlying issue.  Any advice on how to proceed would be
>>>> appreciated.
>>>>
>>>> --
>>>> Steven Hazel
>>>> Sauce Labs
>>>> Cofounder and Director, Development
>>>> http://twitter.com/sahazel
>>>>
>>>
>>>
>>
>>
>> --
>> Steven Hazel
>> Sauce Labs
>> Cofounder and Director, Development
>> http://twitter.com/sahazel
>>
>
>
>
> -- 
> Steven Hazel
> Sauce Labs
> Cofounder and Director, Development
> http://twitter.com/sahazel


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