On Mon, May 17, 2010 at 11:47 AM, Manik Surtani
<manik@jboss.org> wrote:
On 16 May 2010, at 18:35, Philippe Van Dyck wrote:
> Hi all,
>
> in a servlet environment, you sometimes have to claim back a thread for your thread pool.
> Jetty has a nice "denial of service attack" filter and a setting (maxIdleTime) interrupting servlet threads if nothing comes out (nothing is written in the pipe).
>
> Well it does not play well with infinispan. Everybody knows that when you open a stream, the best way to reclaim scarce resources is to close it in a 'finally' statement. What about applying it to infinispan locking mechanism ? ;-)
>
> Calls to acquireLock should be guarded by a finally {releaseLock} (at least to catch an interruptedException)
This is a good point, in the event of a failure (for whatever reason) the lock may still be acquired and should be cleaned up. Care to create a JIRA for this?
> It looks very easy to implement, but since releaseLock does not seems to be called every time in the code, I need help !
>
> The only places where aquireLock is called are CacheLoaderInterceptor.loadIfNeeded and EntryFactoryImpl.wrapEntryForWriting.
>
> And BTW, the locks never expire ... so if you interrupt a thread and the lock is not released, you better say bye bye to the cache entry!
Hmm. While I agree in principle (we could implement a max lock period in the config file), how do you see this working in practice? Maintain timestamps of all acquired locks, and have a maintenance thread regularly check these for locks that have expired (and then interrupt the locking thread)?
I think there is a need for this kind of cleanup whatever the reason a lock is in 'stale' mode.
But IMHO there is a lot of cleanup to do when you interrupt a thread !
What about some timeout callback attached to each lock ?
Now, to test this, you should replay test suites with a 'one millisecond' timeout and ensure that everything is correctly cleaned up.
Great way to improve the quality of the code, but hell of a job!
Cheers,
phil
Cheers
Manik
--
Manik Surtani
manik@jboss.org
Lead, Infinispan
Lead, JBoss Cache
http://www.infinispan.org
http://www.jbosscache.org
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