Hey,
the other day we ran into a situation where our app ran into a OOME situation on heavy
load. It turned out that we had around 290k objects on the Finalizer queue, that
were Statements.
There has been a discussion in the past about finalizers (
see e.g. around http://www.postgresql.org/message-id/BCD42993-CB7B-453F-95B4-09E84A956AB0@me.com ).
I understand that Connection objects are supposed implement a finalizer (is that actually true?),
but here the penalty is not that high, as Connections usually are pooled and are thus long living.
Other JDBC objects like Statements are extremely short lived and the creation rate can be
on a busy application much higher than the finalization rate (which is what we were seeing).
So I wonder if the driver could be rewritten in a way that either
- uses no finalizers for the short lived objects
or
- exist in 2 flavors: a debug version that does excessive logging in the
finalizer if the objects were not yet closed (and stays as is wrt the extra work)
and a production version where
the finalize() methods are removed, so that the objects do not end up
in the finalizer queue and can't pile up under high load.
Developers could then use the devel version and the other driver for production.
Relying on the finalize() method to close/free objects on the PG server is a bad
idea anyway, as there is no guarantee when finalizers run or if they run at all.
Thanks
Heiko
--
Heiko Rupp hwr@pilhuhn.de
Blog: http://pilhuhn.blogspot.com @pilhuhn