A little bit of history...
We have zope as an application server for heavy loaded tech process. We
have high peaks of load several times a day and my question is about how
can we can avoid unused connections to remain in memory after peak is
Before ZODB-3.4.1 connection pool was fixed size of pool_size and that
caused zope to block down while load peaks.
ZODB-3.4.2 that is shipped with Zope-2.8.5 has connection pool that does
not limit the opened connections, but tries to reduce the pool to the
pool_size and this behavior is broken IMO.

Follow my idea...
After peak load I have many (thousands of connections) that have cached
up different objects including RDB  connections.

Hundreds... my mistake.

Huh are you sure? That would mean you have thousands of threads. Or hundreds or ZEO clients. Or hundreds of ZODB mountpoints.

By itself Zope never uses more than one connection per thread, and the number of thread is usually small.

If you see many RDB connections, then it's a RDB problem and not a ZODB problem. Something not releasing RDB connections quick enough, or leaking RDB connections.

Not agree. Can you answer the question? Does self.all.remove(c) mean
that we WANT to destroy connection instance?

The self.all.remove(c) in _ConnectionPool attempts to destroy the connection. If something else has a reference to it once it's closed, then that's a bug, and it shouldn't. It should only keep a weak reference to it at most.

If not then where in ZODB source code i can see connection destruction?
Clearing cache and calling _v_database_connection.close() method?

Sorry I don't know what a _v_database_connection is, it's not in ZODB or transaction code. If it's RDB code I can't help you.

You've just caught me on "thousands" but gave no comments on deletion of
connection instances... but this is the clue to the topic.

Even hundreds of ZODB connections is absurd.
Again, with 4 threads you should never get more than 4 Filestorage connections plus 4 TemporaryStorage connections.


Florent Guillaume, Nuxeo (Paris, France)   CTO, Director of R&D
+33 1 40 33 71 59   http://nuxeo.com   [EMAIL PROTECTED]
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