[infinispan-dev] Distributed Executor remote cancellation

[Sanne Grinovero]

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.

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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>
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