[cdi-dev] async: back to completion future?

Romain Manni-Bucau rmannibucau at gmail.com
Mon Mar 7 08:19:34 EST 2016


2016-03-07 14:15 GMT+01:00 Reza Rahman <reza_rahman at lycos.com>:

> I am really confused now. Why shouldn't Java EE concurrency not be able to
> define a standard way to configure custom executors? You can do that today,
> just in vendor specific ways...
>
>
Cause there are several libs where you don't control the pool and the best
you can do is to wrap the task (Runnable) on your side. Also you can hit it
in background threads you can't enforce to use concurrency spec and finally
you can hit it in fully synchronous way if you execute after the CDI chain
- which is allowed by CDI and TCK-ed so you can need a way to stack the
context to reuse some part after. Last "?": JTA integration: you can also
hit it to save data after @TransactionScoped for audit purposes.


> On Mar 7, 2016, at 5:10 AM, Romain Manni-Bucau <rmannibucau at gmail.com>
> wrote:
>
>
> 2016-03-07 10:57 GMT+01:00 Martin Kouba <mkouba at redhat.com>:
>
>> Dne 7.3.2016 v 09:45 Romain Manni-Bucau napsal(a):
>>
>>> 2016-03-07 9:07 GMT+01:00 Martin Kouba <mkouba at redhat.com
>>> <mailto:mkouba at redhat.com>>:
>>>
>>>
>>>     Dne 7.3.2016 v 09:03 Romain Manni-Bucau napsal(a):
>>>
>>>
>>>         Le 7 mars 2016 08:35, "Martin Kouba" <mkouba at redhat.com
>>>         <mailto:mkouba at redhat.com>
>>>         <mailto:mkouba at redhat.com <mailto:mkouba at redhat.com>>> a écrit :
>>>
>>>           >
>>>           > Dne 6.3.2016 v 15:39 Romain Manni-Bucau napsal(a):
>>>           >
>>>           >> Hi guys,
>>>           >>
>>>           >> as a user having a ComlpetionStage makes me loose some JDK
>>>         utilities,
>>>           >> can we move back to CompletionFuture?
>>>           >>
>>>           >> It would allow for instance:
>>>           >>
>>>           >> // doesn't work with CompletionStage
>>>           >> CompletionFuture.allOf(event1.fireAsync(...),
>>>         event2.fireAsync(...))
>>>           >>        .then(...)
>>>           >
>>>           >
>>>           > Well, this should work if the underlying CompletionStage impl
>>>         supports toCompletableFuture(), i.e. in Weld 3:
>>>           >
>>>
>>>         Yes but it is not natural to convert it IMO = we can do better
>>>
>>>           >
>>>
>>> CompletableFuture.allOf(event1.fireAsync(...).toCompletableFuture(),
>>>         event2.fireAsync(...).toCompletableFuture())
>>>           >
>>>           > AFAIK the default async execution facility of
>>>         CompletableFuture is
>>>         ForkJoinPool.commonPool() which is not a good fit for Java EE.
>>>         Using the
>>>         CompletionStage interface allows us to wrap the async calls
>>>         without the
>>>         specified executor (e.g.
>>>         CompletionStage.thenApplyAsync(Function<? super
>>>         T, ? extends U>)) and supply a default one provided by the impl.
>>>           >
>>>
>>>         Should use the pool in which the evznt is fired then "then step"
>>> is
>>>         synchronous is my sample so all is decided at fire time
>>>
>>>
>>>     I don't talk about your particular example - I understand that it's
>>>     not using async exec (although the "then()" method does not exist).
>>>
>>>
>>> was supposed to represent the different flavours (thenRun, thenCompose,
>>> ...) ;).
>>>
>>> That said I agree on the state switching the pool is better but with
>>> these 2 notes:
>>>
>>> - could be better to hide these poorly designed methods then -> don't
>>> use CompletionXXX but a CDI API with a bridge to CompletionX to let the
>>> user go back on SE tools
>>>
>>
>> Yep, this is one of the possible solutions. On the other hand, I don't
>> think it's poorly designed. CompletionStage defines the "default
>> asynchronous execution facility" and CDI spec states that the
>> CompletionStage returned by fireAsync methods is container-specific. The
>> impl may choose to clarify this "default asynchronous execution facility",
>> i.e. there's place for innovation...
>>
>> - we still don't have a *standard* config for the pool(s) underlying CDI
>>> features so it sounds as poor as SE solution IMO (at least a
>>> core/max/ttl config in beans.xml)
>>>
>>
>> I don't think this should be standardized...
>>
>>
> Why? Typically if you take @Asynchronous (EJB spec) you have already this
> issue and this is often avoided when portability matters for that
> particular reason you don't know how you will behave. Or do you think
> concurrency-utilities solves it?
>
>
>>
>>>
>>>           >
>>>           >>
>>>           >> Romain Manni-Bucau
>>>           >> @rmannibucau <https://twitter.com/rmannibucau> | Blog
>>>           >> <http://rmannibucau.wordpress.com> | Github
>>>           >> <https://github.com/rmannibucau> | LinkedIn
>>>           >> <https://www.linkedin.com/in/rmannibucau> | Tomitriber
>>>           >> <http://www.tomitribe.com>
>>>           >>
>>>           >>
>>>           >>
>>>           >> _______________________________________________
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>>>         <mailto:cdi-dev at lists.jboss.org <mailto:cdi-dev at lists.jboss.org
>>> >>
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>>>           >>
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>>>           >>
>>>           >
>>>           > --
>>>           > Martin Kouba
>>>           > Software Engineer
>>>           > Red Hat, Czech Republic
>>>
>>>
>>>     --
>>>     Martin Kouba
>>>     Software Engineer
>>>     Red Hat, Czech Republic
>>>
>>>
>>>
>> --
>> Martin Kouba
>> Software Engineer
>> Red Hat, Czech Republic
>>
>
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