[ZODB-Dev] Wrong blob file being returned (similar to https://mail.zope.org/pipermail/zodb-dev/2011-February/014067.html )

[steve]

Hi William,

On 07/13/2011 02:26 AM, William Heymann wrote:
> On Tuesday 12 July 2011, steve wrote:
>>  Hi,
>>
>>  I have a setup where 4 ZEO clients running on separate machines connect to
>>  a single DB server which runs on a different system by itself. The ZEO
>>  clients and the DB server all are at version ZODB3-3.10.2. Now, since the
>>  last few weeks some of our users have been reporting that they
>>  occasionally see incorrect images being returned.
>
> One thing you may want to look at is the load balancer. Apache has a bug that
> keeps being opened and closed again for swapping data between requests under
> load. Because it happens at the apache level and not the zope level you will
> never see this problem in any of the zope logs.
>
hmmm, interesting. Since we are using Amazon's Elastic LB to load balance these 
app. servers running of EC2 instances and we do not have any direct access to 
the ELB logs or systems, pining this problem on the ELB might be difficult 
(although AFIAK, the ELB setup also uses apache -- I could be mistaken though).

If it isn't too much effort could you please point me to the apache bug you 
mentioned ?

> Just make sure you don't have a similar situation or you could end up
> debugging the wrong thing to a huge waste of time. In my case I spent a lot of
> time debugging zope and when I finally discovered it was apache that was
> screwing up I ended up just dumping apache for nginx.
>

Thanks for the info. I shall keep a lookout for this.

cheers,
- steve

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