tomcat-users mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Elli Albek <e...@sustainlane.com>
Subject Re: ConnectionPool question
Date Tue, 03 Nov 2009 20:13:56 GMT
No, you do not need to close the XXXMetaData classes.

E

On Tue, Nov 3, 2009 at 12:02 PM, Josh Gooding <josh.gooding@gmail.com>wrote:

> One more question on bleeding resources.  When closing RS / statement /
> connections.  Do I have to do anything with the MetaData if I got that as
> well?  (I.E Do I explicitly have to close the metadata as well?)
>
> Josh
>
> On Tue, Nov 3, 2009 at 2:01 PM, Josh Gooding <josh.gooding@gmail.com>
> wrote:
>
> > Elle,
> >
> > I am going to dig into this code and check it out.  I want to know more
> > about how to use threadlocal and filters.  (Sorry I'm not as experienced
> in
> > Tomcat as some for you gurus here).
> >
> > The code looks promising and I like the 2nd option due to the fact that
> > each HTTP req. only has one connection (which should drop the overhead
> > immensely) however for right now, I just want to fix the bleeding issue
> > (which it seems that I have caught a good portion of them), so I'll use
> my
> > legacy code, but during a "minor" code release, I can definitely look
> into
> > rolling this out.  I am getting a ton of "abandoned" connection warnings
> in
> > the console window, so I need to find out where these are coming from
> now.
> >
> > I don't know where to begin thanking you guys but thank you.  I've gotten
> > more mentoring here on this listing than I have in 2 years at my current
> > employer.  Thank you all again.
> >
> > - Josh
> >
> >
> > On Mon, Nov 2, 2009 at 3:40 PM, Christopher Schultz <
> > chris@christopherschultz.net> wrote:
> >
> >> -----BEGIN PGP SIGNED MESSAGE-----
> >> Hash: SHA1
> >>
> >> Elli,
> >>
> >> On 11/2/2009 4:08 AM, Elli Albek wrote:
> >> > I think you can have a solution without changing your code.
> >> >
> >> > Try something like this:
> >> >
> >> > getConnection() static method should get the connection, and add it to
> a
> >> > list that you keep in threadlocal.
> >> >
> >> > recycleConnection() should close the connection and remove the
> >> connection
> >> > object from thread local.
> >> >
> >> > Add a servlet filter that closes all connections in thread local. The
> >> filter
> >> > calls next filter, and in a finally block get the connections from
> >> thread
> >> > local, close all of them, and clear the list in thread local.
> >>
> >> This is a horrible, nasty hack and it's entirely brilliant!
> >>
> >> I would change Elli's implementation just slightly, and actually write
> >> your own DataSource implementation that piggybacks on another one.
> >> Basically, you just wrap the DataSource that Tomcat provides either by:
> >>
> >> a. Using JNDI to look-up the Tomcat-created JNDI DataSource and just
> >>   writing the plumbing code to pass everything through
> >> b. Actually subclass the DataSource class(es) provided by Tomcat and
> >>   use /those/ in your <Resource> configuration.
> >>
> >> I would also not make any of this static... there's just no reason to do
> >> so, especially if your DataSource object is in the JNDI context.
> >>
> >> Although the /real/ solution is to fix the code, I really like this
> >> solution for a couple of reasons:
> >>
> >> 1. It requires no wrapping of Connection, Statement, etc. objects
> >>   (which is entirely miserable if you've ever had to do it)
> >> 2. It requires no changes to your code whatsoever (if you use my
> >>   DataSource-wrapping suggestion above)
> >> 3. You won't end up closing your connection, statement, result set, etc.
> >>   too early because your code has completed execution (unless you
> >>   are using JDBC resources across requests, which is another story)
> >>
> >> What this won't help, unfortunately is:
> >>
> >> * Closing your ResultSet and Statement objects (though this can be
> >>  solved by wrapping the Connection, Statement, etc. objects handed-
> >>  out by your DataSource. Yes, it's miserable.)
> >>
> >> > This will allow you to keep your legacy code. As far as I remember
> DBCP
> >> has
> >> > an option to close the result sets and statements when you close the
> >> > connection. If not this will partly work.
> >>
> >> I don't believe commons-dbcp has this capability at all. I'm willing to
> >> read any documentation to the contrary, though.
> >>
> >> > Version 2: Advanced
> >> >
> >> > Keep the actual connection in thread local. You will have one
> connection
> >> per
> >> > HTTP request. getConnection() should be something like
> >> >
> >> > public static /* NOT synchronized */ Connection getConnection(){
> >> >
> >> > Connection c = ...// get the connection from thread local
> >> >
> >> > if (c != null)
> >> >
> >> > return c;
> >> >
> >> > Connection c = ...// get the connection from JNDI/DBCP
> >> >
> >> > // put connection in thread local
> >> >
> >> > return c;
> >> >
> >> > }
> >>
> >> I like this technique, too. You just have to decide if it's acceptable
> >> for your webapp to re-use connections. I can't imagine why that would be
> >> a problem, but it's worth considering before you blindly do it. This
> >> optimization can save you from deadlock (though you're killing-off
> >> connections after 15 seconds anyway) and should significantly improve
> >> the performance of your webapp because you won't be bleeding so many
> >> connections: you're limited to bleeding one connection per request
> >> instead of potentially dozens.
> >>
> >> > recycleConnection(){
> >> >
> >> > // empty, connection will be recycled by filter.
> >> >
> >> > }
> >>
> >> I would actually allow recycleConnection to close the connection, and
> >> have the filter call recycleConnection. That way, as you improve your
> >> webapp's code, the connections will be closed as soon as possible
> >> instead of waiting until the request is (mostly) finished.
> >>
> >> Again, Elli, a great suggestion!
> >>
> >> - -chris
> >> -----BEGIN PGP SIGNATURE-----
> >> Version: GnuPG v1.4.10 (MingW32)
> >> Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/
> >>
> >> iEYEARECAAYFAkrvQ8AACgkQ9CaO5/Lv0PDOSACeJfqgaXmrySSKItQHji2K6UzK
> >> hmsAoKIAhRAgwzI/QN8SPdVGkBbewA2a
> >> =Mqjn
> >> -----END PGP SIGNATURE-----
> >>
> >> ---------------------------------------------------------------------
> >> To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
> >> For additional commands, e-mail: users-help@tomcat.apache.org
> >>
> >>
> >
>

Mime
  • Unnamed multipart/alternative (inline, None, 0 bytes)
View raw message