[cdi-dev] inheritance of cdi scopes
Reza Rahman
reza_rahman at lycos.com
Sun Mar 6 14:59:26 EST 2016
As far as I know this is precisely the sort of thing that the EE concurrency spec is intended for. It is supposed to copy over everything from the underlying thread local context into the new thread for all EE managed components to function. Since CDI beans are also EE container managed, it also applies to CDI beans as well. The EE vendor is supposed to make sure this works properly.
I don't think the concurrency utilities specifically lists APIs for which thread context propagation should work. If this doesn't work in a specific implementation it's most likely because they didn't take CDI into account in their own EE concurrency implementation.
> On Mar 6, 2016, at 2:45 PM, John D. Ament <john.d.ament at gmail.com> wrote:
>
> 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 | Blog | Github | LinkedIn | Tomitriber
>>>>>>>>
>>>>>>>> 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 | Blog | Github | LinkedIn | Tomitriber
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>>>>>>>>>
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