Re: Connection pool deadlock - Mailing list pgsql-jdbc

Hi Dave,

The reason for multiple connections is that the Objects in my
application contact the database directly for their persisitency
requirements. And I am not creating any connection object in that
jsp page directly. Instead I'm making calls to those objects and
they in-turn contact the database to get  the data. This is the
reason for multiple connections. I think I can reduce the number of
concurrent connections required while rendering that page but I
cannot eliminated it completely.

Me too had the idea of keeping the pool size as an integral
multiple of 3 but didn't work :(


--- Dave Cramer <Dave@micro-automation.net> wrote:
> Anil,
>
> Other than re-coding which is the real solution; (There is no
> reason for
> more than on connection per request) make sure your pool has
> multiple of
> 3 connections, ie 9, 12, 15, but not 10.
>
> Dave
> On Fri, 2003-02-28 at 00:25, Anil Kumar wrote:
> > 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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> --
> Dave Cramer <Dave@micro-automation.net>
>


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