If I close the RS, can I still use the MD? On Tue, Nov 3, 2009 at 3:13 PM, Elli Albek <e...@sustainlane.com> wrote:
> 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 > > >> -----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-unsubscr...@tomcat.apache.org > > >> For additional commands, e-mail: users-h...@tomcat.apache.org > > >> > > >> > > > > > >