[Zope] Re: Zope hangs when database takes too long to respond

[Tres Seaver]

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Sinang, Danny wrote:
> Sorry for the typo error. 
>  
> The subject should read "hangs", not "hands" .
> 
> ________________________________
> 
> From: zope-bounces at zope.org [mailto:zope-bounces at zope.org] On Behalf Of
> Sinang, Danny
> Sent: Wednesday, September 06, 2006 10:56 PM
> To: zope at zope.org
> Subject: [Zope] Zope hands when database takes too long to respond
> 
> 
> Hello,
>  
> We wrote an application (on Zope v2.7.6-final) that queries a MySQL
> database via ZMySQLDA v2.0.8.
>  
> Whenever the MySQL server experiences heavy load, Zope seems to hang,
> such that we can't even access the ZMI.
>  
> Is this a bug in version 2.7.6 or ZMySQLDA ?

It is a "known" limitation of Zope, which has a set number of "worker
threads" available to service user requests.  If a worker thread blocks
(e.g., waiting for MySQL), it is not able to do any work for other
pending requests.

You can tweak the number of threads in your zope.conf file, via the
'zserver-threads' directive (the default value is 4).  If you do
increase this value, you also need to increase the number of database
connections avialble (via 'pool-size') which will increase the RAM
required by your appserver.

> Or are there some settings I can tweak to adjust some database
> connection timeout value ?

Not that I know of.


Tres.
- --
===================================================================
Tres Seaver          +1 202-558-7113          tseaver at palladion.com
Palladion Software   "Excellence by Design"    http://palladion.com
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