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Connection pool deadlock

From: Anil Kumar <techbreeze(at)yahoo(dot)com>
To: pgsql-jdbc(at)postgresql(dot)org
Subject: Connection pool deadlock
Date: 2003-02-28 05:25:08
Message-ID: 20030228052508.79222.qmail@web13903.mail.yahoo.com (view raw or flat)
Thread:
Lists: pgsql-jdbc
Hi All,

I'm facing a problem with connection pooling. I'm using the
pg73jdbc3.jar
with PG 7.2 on RH 7.3.

This is a Web application running on Tomcat. To render one of its
pages it
requires three concurrent connections to the database. It requests
one
connection after another and return them in the reverse order (the
last
obtained connection is returned first and so on). This creates a
dead-lock
if multiple requests are coming for this particular page. For
example if  
the pool size is 10 and if the application is getting 4
simultaneous
requests for this page I found that the connection allocation
happens in
the following way:

conn 1 -> request 1
conn 2 -> request 2
conn 3 -> request 3
conn 4 -> request 4
conn 5 -> request 1
conn 6 -> request 2
...
conn 10 -> request 2

Here no request (or thread) will get enough number of connections
to
complete the request and all requests will go to an indefinite wait
state.
Of course this happens only when the connection requests reaches
the pool
capacity.

I guess that some of you must have experienced this problem. What
is the
way out (other that re-coding the application to complete the
request with
single connection)?

best regards
   Anil

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Subject: Re: Connection pool deadlock
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