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From "Cameron, Scott" <scott.came...@sap.com>
Subject [dbcp] Handling many different user accounts over time
Date Wed, 07 Dec 2011 16:27:58 GMT
Hi,

I'm considering using either SharedPoolDataSource or PerUserPoolDataSource to do some connection
pooling but I've noticed that there doesn't seem to be any way to configure an upper bound
on the total number of connections in the pool across all users.

For example, say I have 5,000 named users in my database.  Any of the 5,000 can come in to
request a DB connection at any time, but likely no more than, say, 100 of them will ever be
active at a particular point in time.  If I want to allow 3 connections per user, how do I
ensure that I'm not eventually going to end up with 15,000 open connection over time.

It looks like the "maxTotal" setting on the GenericObjectPool (and GenericKeyedObjectPool)
can be used to control this such that when this absolute upper bound is reached on the pool
the least recently used 15% of connections will be recycled.  But neither SharedPoolDataSource
nor PerUserPoolDataSource expose any way to configure maxTotal.

Is there another recommended way to solve this problem?  What do high-traffic web containers
like Tomcat or JBoss do to deal with this scenario (if they do deal with it)?

Thanks in advance!

scott

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