Very long time to commit or close connections

Hi everyone,

I'm running into a rather serious problem in a production application using
PostgreSQL.

We've got about a connection every 4 seconds being created to the database.
Most of the time, this causes no problems at all.  Occasionally, though, with
no apparent reason, the database will act up for some time (as little as 10
minutes, or as long as 45 minutes).  During that time, it accepts connections
and runs queries and statements with no problems, but hangs when closing the
connections.  After the time period expires, the database will wake up and all
connections that have been waiting will simultaneously return from the JDBC
Connection.close() method.

Unfortunately, the problem is only occurring at a remote customer site to
which we have limited access, and sometimes requires multiple days of running
time to reproduce.  As a result, it's hard to see what's happening at the
instant this happens.  I'm trying to gather more information, but don't have
it right now.

So right now, my question is this: does this sound familiar to anyone, and
what information would you look for in troubleshooting this?

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