[Zope] Problem with Zodb connections pool

Tres Seaver tseaver at palladion.com
Wed Oct 14 06:51:42 EDT 2009

Hash: SHA1

Claudio Battaglino wrote:
> Hi all,
> I've a system with Zope 2.8.8 that since some weeks is very slow.
> The python process keeps busy the CPU (98-99%) and the memory used by
> the process is growing up.
> Every day a script makes a pack of the ZODB and restarts Zope so the
> Data.fs size is stable (about 350MB).
> In the event.log I can see many of this warnings:
> 2009-10-14T11:59:14 WARNING ZODB.DB DB.open() has 8 open connections
> with a pool_size of 7
> What does it mean?

Likely something in your application is leaking connections (and
therefore RAM).  Normally each "worker" thread gets a connection from
the pool at the start of the request, uses it, and then returns it to
the pool at the end of the request.

If you are using the default configuration for number of threads (4),
then something has leaked four connections (assuming your server is busy
at the time you see that log message).  You should examine the "Debug
Information" page in the ZMI control panel to get information for
diagnosing the leak.

> I can see also some of these messages:
> 2009-10-14T12:14:16 INFO ZODB.Conflict database conflict error...
> According to you, are the two messages related?

No.  Conflict errors occur normally, whenever "simultaneous" requests
cause writes to the same objects.  The request whose transaction commits
"later" gets retried, up to three times;  if it still conflicts, then
the request returns an error, and you see the message in your logfile.

- --
Tres Seaver          +1 540-429-0999          tseaver at palladion.com
Palladion Software   "Excellence by Design"    http://palladion.com
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