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From "Bill Au" <bill.w...@gmail.com>
Subject Re: Can servlets safely spawn threads?
Date Mon, 29 Jan 2007 15:38:19 GMT
If you are spawning threads from your servlet, make sure that they are
cleaned up when
the servlet is destroyed.  Otherwise, you will have a thread leak.  I have
ran into this problem
when the webapp is reloaded without restarting the server.  Each leaked
thread has a
reference to its classloader, preventing that classloader from being garbage
collected.
Reload enough time will run the perm space out of memory.

Bill


On 1/29/07, Christopher Schultz <chris@christopherschultz.net> wrote:
>
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> Danny,
>
> David Delbecq wrote:
> > 1) Your servlet must always take care to finish all Threads it has
> > spawned. This mean when servlet gets unloaded, you must have provided a
> > mecanism in your servlet to stop all running threads your servlet has
> > created. Remaining Threads not handled by container can either cause
> > tomcat to not stop when requested or prevent garbage collecting of
> > webapp when reloading.
>
> Consider using an existing thread pool component. It should have a
> graceful shutdown capability already built into it. David is right: you
> have to make sure to shut it down when appropriate.
>
> > In general, try to avoid spawning your own thread.
>
> I agree, which is why I recommend using a thread pool. Yes, you are
> still technically spawning your own threads (the container will not do
> it for you), but the point is that you will not be spawning a thread for
> each request.
>
> Set up your thread pool to have a "reasonable" number of threads for
> your application. You do not want to have loads of users submit jobs
> that will each spawn a new thread. If you run out of threads in the
> thread pool, you simply tell the user to come back later. Management of
> this type of resource is essential to maintaining a stable and useful
> system.
>
> - -chris
>
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