No, you do not need to close the XXXMetaData classes.
E
On Tue, Nov 3, 2009 at 12:02 PM, Josh Gooding <josh.good...@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.good...@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 <
> > ch...@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
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>
