Re: Tomcat reuses threads and connection instances
On 1/26/11 11:37 PM, Christopher Schultz wrote: > Blake, > > On 1/26/2011 4:05 PM, Blake McBride wrote: >> The first time a particular web service is called tomcat starts a thread to >> run it on and creates an instance of the class that implements the web >> service. All fine. However, if after the first call to the web service >> completes another call to the same web service occurs, tomcat reuses the >> same thread and the same instance. Of course this gives me old values for >> thread local storage and instance variables for that web service. > > Oh noes!!!111!!!ELEVEN > > Seriously, this is how the server world works. > >> This is highly unexpected. > > Perhaps by you, but this behavior is entirely intentional. > >> Is there a way to configure tomcat to have it give me a new instance of the >> web service class each time? > > That depends: when you say "web service", what do you mean? Are you > using a library like Apache Axis or do you have a (relatively) simple > servlet handling the requests? > > The rules of thumb are: > > 1. Don't use ThreadLocal unless you > a) Know what you're doing > b) Clean up after yourself > and > c) Know what you're doing +1 Axis 1.4 has issues in this regard. p > 2. Don't use any class members that aren't expected to be used for all >requests for all time. Basically, that means don't use them. Instead, >use locals in your service() (or doGet/doPost/whatever) method >and/or use request attributes to store your data. > >> In terms of the repeated thread use and thread local storage I have, for the >> time being, started manually resetting the thread local storage. Is there a >> conventional solution to this problem? > > Your thread should reset ThreadLocals when you're done using the thread: > at the end of the request. Don't forget to handle error conditions and > clean up in finally blocks. > > Why are you using ThreadLocals in the first place? The only legitimate > uses I've seen for them are performance optimizations where the > ThreadLocal actually /should/ outlive the request and weird stuff like > passing data to Log4j loggers through lazy API (non-)usage. I'm not > convinced ThreadLocals are a good idea at all. > > -chris - To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org 0x62590808.asc Description: application/pgp-keys signature.asc Description: OpenPGP digital signature
Re: Tomcat reuses threads and connection instances
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Blake, On 1/26/2011 4:05 PM, Blake McBride wrote: > The first time a particular web service is called tomcat starts a thread to > run it on and creates an instance of the class that implements the web > service. All fine. However, if after the first call to the web service > completes another call to the same web service occurs, tomcat reuses the > same thread and the same instance. Of course this gives me old values for > thread local storage and instance variables for that web service. Oh noes!!!111!!!ELEVEN Seriously, this is how the server world works. > This is highly unexpected. Perhaps by you, but this behavior is entirely intentional. > Is there a way to configure tomcat to have it give me a new instance of the > web service class each time? That depends: when you say "web service", what do you mean? Are you using a library like Apache Axis or do you have a (relatively) simple servlet handling the requests? The rules of thumb are: 1. Don't use ThreadLocal unless you a) Know what you're doing b) Clean up after yourself and c) Know what you're doing 2. Don't use any class members that aren't expected to be used for all requests for all time. Basically, that means don't use them. Instead, use locals in your service() (or doGet/doPost/whatever) method and/or use request attributes to store your data. > In terms of the repeated thread use and thread local storage I have, for the > time being, started manually resetting the thread local storage. Is there a > conventional solution to this problem? Your thread should reset ThreadLocals when you're done using the thread: at the end of the request. Don't forget to handle error conditions and clean up in finally blocks. Why are you using ThreadLocals in the first place? The only legitimate uses I've seen for them are performance optimizations where the ThreadLocal actually /should/ outlive the request and weird stuff like passing data to Log4j loggers through lazy API (non-)usage. I'm not convinced ThreadLocals are a good idea at all. - -chris -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.10 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEUEARECAAYFAk1AsB4ACgkQ9CaO5/Lv0PB0KgCgq/oBUPbokm0RxU2TJUUbTc5o P14AmNWkViWqWDzayx274G/ghV0oStw= =xJXy -END PGP SIGNATURE- - To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
Tomcat reuses threads and connection instances
Greetings, I have a web service app that runs under tomcat. I just noticed the following unexpected behavior. The first time a particular web service is called tomcat starts a thread to run it on and creates an instance of the class that implements the web service. All fine. However, if after the first call to the web service completes another call to the same web service occurs, tomcat reuses the same thread and the same instance. Of course this gives me old values for thread local storage and instance variables for that web service. This is highly unexpected. Is there a way to configure tomcat to have it give me a new instance of the web service class each time? In terms of the repeated thread use and thread local storage I have, for the time being, started manually resetting the thread local storage. Is there a conventional solution to this problem? Thanks. Blake McBride
