[Proxool-developer] Spurious connections caused by Prototyper's apparently wrong connectionCount

[Hrvoje N. <hn...@xe...>]

We're having a problem deploying Proxool 0.8.3 with Oracle.  The
relevant settings are:

jdbc-0.proxool.maximum-connection-count 30
jdbc-0.proxool.minimum-connection-count 2
jdbc-0.proxool.house-keeping-sleep-time 60000
jdbc-0.proxool.house-keeping-test-sql select * from dual
jdbc-0.proxool.test-before-use true
jdbc-0.proxool.maximum-active-time 240000
jdbc-0.proxool.maximum-connection-lifetime 1800000
...

So proxool should maintain no less than 2 and no more than 30
connections to the database.  But, over time, it appears that proxool
opens more connections, eventually exhausting Oracle's
SESSIONS_PER_USER limit.  All the connections are usable and the
additional ones are opened at times when there there are other usable
connections available.  For example, when creating the 33rd
connection, Proxool's log contains:

2005-09-27 01:36:57 DEBUG [ConnectionPool] [Thread-18]: 1003445 -000257 (04/32/00) - Connection #1646 tested: OK
2005-09-27 01:36:57 DEBUG [chatdate] [Prototyper]: 1003446 -000257 (04/33/00) - Connection #1666 created to achieve minimum of 2 = AVAILABLE

04/32/00 shows that ConnectionPool is aware that it has a total of 32
connections, 28 of which are available, and yet the Prototyper thinks
it has less than two open connections and is trying to open more to
make up for the perceived shortage.  Examining established connections
with netstat shows that ConnectionPool's numbers are correct.

A possible cause for this problem was outlined by Peter Radics in his
message from Jan 11th, http://tinyurl.com/7eb77/.  He noticed that
each time HouseKeeper sweeps a connection that has been active for too
long, connectionCount gets decremented twice.  However, no one
responded to that message and I don't know if this problem has been
fixed in the development sources.  I'm reluctant to apply his patch
unchanged because it feels like a kludge and because the last part
contains an increment I don't understand.

Another problem I noticed with the Prototyper code is that it lacks
synchronization when decrementing connectionCount.  That cannot be
good, although it is probably not the cause of this particular
problem.

Are you aware of a fix or a workaround for this?  Thanks for your
help.