[infinispan-dev] Distributed Executor remote cancellation

[Gustavo Fernandes]

On Wed, Mar 30, 2016 at 6:26 PM, Sanne Grinovero <sanne at infinispan.org>
wrote:

> On 30 March 2016 at 17:40, William Burns <mudokonman at gmail.com> wrote:
> > You can still attempt to cancel a task.  This email is specifically about
> > interruption though.  Let me explain the nuances in a bit more detail.
> >
> > With the suggestion we would still fully support if the task hasn't yet
> > started that it would be cancellable.
> >
> > However when you cancel a task, there is an mayInterruptIfRunning
> boolean.
> > If mayInterruptIfRunning is true and the task is already running it will
> try
> > to interrupt the thread processing it.  This is what this email trail is
> > about.  We all know that java interruption can be flaky to begin with and
> > then adding a remote aspect to it, it becomes even more unreliable.
> >
> > So do you guys think we need to support "interrupting" a task in
> progress?
>
> Yes, absolutely! Resources are precious :)
>
> See also the reasoning of our old friend:
>  - https://corner.squareup.com/2016/01/query-sniper.html
>
> Take the example of a non-correctly tuned Hibernate Search "rebuild
> all indexes" task. On a non-trivial data set it might need to run for
> weeks... you need a way to kill it.
>


That's the case of our Mass Indexer: one of the motivations of making it
return a Future was
the possibility of cancelling tasks, capability offered by the Distributed
Executor.

Gustavo


>
> Thanks,
> Sanne
>
> >
> >  - Will
> >
> > On Wed, Mar 30, 2016 at 12:29 PM Tristan Tarrant <ttarrant at redhat.com>
> > wrote:
> >>
> >> I agree with Sanne, we need cancellable  tasks.
> >>
> >> Tristan
> >>
> >> On 30/03/2016 18:19, Sanne Grinovero wrote:
> >> > The term "Interruption" might have been too specific, but being able
> >> > to cancel a task seems essential to me.
> >> >
> >> > On 30 March 2016 at 17:04, William Burns <mudokonman at gmail.com>
> wrote:
> >> >> Recently we have been moving a lot of our methods that return Future
> >> >> [1] to
> >> >> CompletableFuture [2].  Unfortunately the latter, CompletableFuture,
> >> >> doesn't
> >> >> allow for cancellation of the future, since there is no thread tied
> to
> >> >> it.
> >> >> So I am proposing that our DistributedExecutorService [3] no longer
> >> >> allows
> >> >> for interruption of remote threads on a cancellation.  This way we
> can
> >> >> have
> >> >> our distributed executor service return CompletableFuture instances
> >> >> which do
> >> >> not support interruption.
> >> >>
> >> >> Also to note that DistributedExecutorService extends ExecutorService
> >> >> which
> >> >> returns a normal Future which is documented as allowing cancellation.
> >> >> In
> >> >> this case I would just document on DistributedExecutorService that we
> >> >> don't
> >> >> support interruption anyways.
> >> >>
> >> >> Does anyone require the use of interruptable tasks with Distributed
> >> >> Executor?
> >> >>
> >> >> Thanks,
> >> >>
> >> >>   - Will
> >> >>
> >> >> [1]
> >> >>
> >> >>
> https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/Future.html
> >> >> [2]
> >> >>
> >> >>
> https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CompletableFuture.html
> >> >> [3]
> >> >>
> >> >>
> https://docs.jboss.org/infinispan/8.1/apidocs/org/infinispan/distexec/DistributedExecutorService.html
> >> >>
> >> >> _______________________________________________
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> >> >
> >>
> >> --
> >> Tristan Tarrant
> >> Infinispan Lead
> >> JBoss, a division of Red Hat
> >> _______________________________________________
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> >> https://lists.jboss.org/mailman/listinfo/infinispan-dev
> >
> >
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