[cdi-dev] inheritance of cdi scopes

Sun Mar 6 14:45:15 EST 2016

The section of the spec you link to makes no references to threads.  6.3
makes some notes about normal scopes and threads, and specifically says
that a context is bound to one or more threads.

I think what's happened is that over the years, people have simply bound
HTTP Request == single thread, but when async processing was introduced no
one thought to clarify that the spawning of a child thread from the
original HTTP request retains the parent's context.

This is another requested feature, but looks more like a bug or gap in the
spec.

John

On Sun, Mar 6, 2016 at 2:37 PM Romain Manni-Bucau <rmannibucau at gmail.com>
wrote:

> 2016-03-06 20:25 GMT+01:00 Reza Rahman <reza_rahman at lycos.com>:
>
>> Let's see. I suspect the specification text for EE concurrency is generic
>> enough for implementations to also be able to cover CDI scopes or any other
>> Java EE API context propagation needs. This means the issue needs to be
>> solved at the individual implementation level. Changing anything in the
>> spec is probably just unnecessary ceremony in this case.
>>
>>
> Then 1. concurrency- utility can't be reliable for "EE" users, 2. CDI
> still prevent it to work since it would violate the spec to propagate it
> while request scope is bound to another thread (
> http://docs.jboss.org/cdi/spec/1.1/cdi-spec.html#request_context handles
> async listener but not the main AsyncContext part).
>
>
>> On Mar 6, 2016, at 2:15 PM, Romain Manni-Bucau <rmannibucau at gmail.com>
>> wrote:
>>
>>
>> 2016-03-06 19:42 GMT+01:00 Reza Rahman <reza_rahman at lycos.com>:
>>
>>> This frankly surprises me. I'll check the specification text. This might
>>> indeed just be an implementation bug. The EE concurrency utilities are
>>> supposed to be copying all relevant context. If this is an issue than it
>>> has to be that it is not copying enough of the HTTP request context for CDI
>>> to work.
>>>
>>>
>> The issue is not technical since I got it working but needed to reverse.
>> From my understanding ee concurrency utilities was done in a time CDI was
>> not there so it just ignored it somehow and it hasnt been updated when
>> integrated to the spec. Now with the wording of the CDI - and TCK - it is
>> impossible to make it working since request scope is bound the thre request
>> thread - and not the request. Side note: same applies to session scope and
>> conversation.
>>
>>
>>> Surely the Red Hat folks can quickly shed some light here since they
>>> implement essentially this whole stack?
>>>
>>> On Mar 6, 2016, at 1:30 PM, Romain Manni-Bucau <rmannibucau at gmail.com>
>>> wrote:
>>>
>>> 2016-03-06 19:20 GMT+01:00 Reza Rahman <reza_rahman at lycos.com>:
>>>
>>>> Can you kindly try to make the example a bit simpler? It's important to
>>>> make the case for how likely this is supposed to occur in most business
>>>> applications.
>>>>
>>>> Also, other than making sure that the executor service is propagating
>>>> thread local request contexts correctly what other solution are you
>>>> proposing? Did you check the specification? How sure are you that this
>>>> isn't simply an implementation bug?
>>>>
>>>> As far as I know the executor service is supposed to be preserving all
>>>> relevant parts of the EE context?
>>>>
>>>>
>>> Not in concurrency-utilities for EE at least. That was the first impl I
>>> did then Mark pointed out it was violating CDI spec and request scope
>>> definition. There is a kind of contracdiction there cause
>>> concurrency-utilities doesn't integrate with CDI at all but we can also see
>>> it the opposite way: CDI doesn't provide any way to propagate a context in
>>> another thread. Both point of view are valid so we need to see where we
>>> tackle it.
>>>
>>>
>>>> On Mar 6, 2016, at 12:35 PM, Romain Manni-Bucau <rmannibucau at gmail.com>
>>>> wrote:
>>>>
>>>> does https://gist.github.com/rmannibucau/d55fce47b001185dca3e help?
>>>>
>>>> Idea is to give an API to make:
>>>>
>>>> public void complete() {
>>>> try {
>>>> asyncContext.complete();
>>>> } finally {
>>>> auditContext.end();
>>>> }
>>>> }
>>>>
>>>> working without hacky and almost impossible context pushing (cause of
>>>> injections nature you are not supposed to know what to push in the context
>>>> when going async).
>>>>
>>>>
>>>>
>>>> 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>
>>>>
>>>> 2016-03-06 16:40 GMT+01:00 Reza Rahman <reza_rahman at lycos.com>:
>>>>
>>>>> Can you kindly share an annotated code example of the proposed
>>>>> solution so we can all follow and discuss this?
>>>>>
>>>>> On Mar 6, 2016, at 9:31 AM, Romain Manni-Bucau <rmannibucau at gmail.com>
>>>>> wroteshar:
>>>>>
>>>>> Hi guys,
>>>>>
>>>>> spoke on concurrency utilities about the ability to inherit a cdi
>>>>> scope. Idea is to follow request scope more than cdi spec allows. First
>>>>> thought it was a concurrency utilities thing but Reza mentionned can be a
>>>>> CDI one so here it is.
>>>>>
>>>>> Sample:
>>>>> In a servlet i get MyBean which is @RequestScoped, I do some set on
>>>>> it. The i go async (AsyncContext) and trigger a task in another thread. It
>>>>> would be neat - and mandatory in some case by the loose coupling nature of
>>>>> CDI - to get the *same* MyBean *instance* in this thread. With a direct
>>>>> dependency you can easily use message passing pattern - but you loose the
>>>>> loose coupling cause you need to know until which level you unwrap, think t
>>>>> principal case which has 2-3 proxies!. However in practice you have a lot
>>>>> of undirect dependencies, in particular with enterprise concerns (auditing,
>>>>> security...) so you can't really do it easily/naturally.
>>>>>
>>>>> Bonus:
>>>>> One very verbose way is to be able to kind of push/pop an existing
>>>>> context in a thread - wrappers doing it on a Runnable/Consumer/Function/...
>>>>> would be neat.
>>>>>
>>>>> Question:
>>>>> Would CDI handle it in 2.0?
>>>>>
>>>>> Side note: this is really about the fact to reuse a "context context"
>>>>> (its current instances map) in another thread the more transparently
>>>>> possible and match the user vision more than a technical question for now.
>>>>>
>>>>>
>>>>> 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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>>>>
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