[Zope] Zope 2.8.4 strange behavior

[Chris McDonough]

On Nov 27, 2005, at 8:13 PM, Dennis Allison wrote:

> here to begin to track this one down.  The failure
> is spontaneous and apparently not triggered by any readily  
> distinguishable
> inputs or pattern of inputs.  The behavior smells a bit of resource  
> limits
> or process synchronization problems, but there is not real evidence  
> for
> either being the root cause.   I am not sure what monitoring I  
> should be
> doing to help locate the source of the problem.
>
> Has anyone seen seen a similar problem?  Any advice as to how to  
> proceed?

A pool of database connections is kept around to pull from for each  
ZODB database you have.  By default, there are 7 of them per  
database; this number can be changed by the pool-size parameter in  
the <zodb_db> section in your config file.  These connections are  
returned to the pool when a connection is closed.  This usually  
happens when a transaction that is using that connection completes.

The symptom you're describing has happened to me in the past.  Zope  
stops serving requests and my CPU is not pegged (it's not hitting the  
CPU hard via an infinept loop I've made).  I usually end up tracking  
it down to the fact that my instance is somehow leaking database  
connections.  The connection is never closed so it never gets  
returned to the pool.  This can happen when there is an error during  
a transaction commit or abort.

Since you've previously posted to the list with commit errors of just  
this kind, it seems like that would be the logical place to start.   
You didn't mention seeing any of these errors, though, so if you  
don't see any of those in the event log, I'm not sure where to go  
from there other than debugging by binary exclusion which can be  
impossible when the failures happen so far apart. :-(

- C