[cdi-dev] inheritance of cdi scopes
Stephan Knitelius
stephan at knitelius.com
Mon Mar 7 05:27:20 EST 2016
>>"
>>Tasks that are submitted to a managed instance of ExecutorService may
still be running after the lifecycle of the submitting >>component.
Therefore, CDI beans with a scope of @RequestScoped, @SessionScoped, or
@ConversationScoped are not >>recommended to use as tasks as it cannot be
guaranteed that the tasks will complete before the CDI context is
destroyed.
>>"
>
>States that the context is not inherited, is that what you mean?
Sounds more like a warning that the CDI context may be destroyed prior to
completion of the asynchronous task. Therefor we might be able to clear
this up on the CDI side, by keeping contexts alive as long as they are
associated with > 1 executing threads.
On Mon, 7 Mar 2016 at 09:50 Romain Manni-Bucau <rmannibucau at gmail.com>
wrote:
> "
> Tasks that are submitted to a managed instance of ExecutorService may
> still be running after the lifecycle of the submitting component.
> Therefore, CDI beans with a scope of @RequestScoped, @SessionScoped, or
> @ConversationScoped are not recommended to use as tasks as it cannot be
> guaranteed that the tasks will complete before the CDI context is
> destroyed.
> "
>
> States that the context is not inherited, is that what you mean?
>
>
>
> 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>
>
> 2016-03-07 5:57 GMT+01:00 Reza Rahman <reza_rahman at lycos.com>:
>
>> The specification currently references pretty much all the major CDI
>> scopes specifically with the issue of propagation and lifecycle in mind.
>> Please see section 2.3.
>>
>> On Mar 6, 2016, at 11:53 PM, Mark Struberg <struberg at yahoo.de> wrote:
>> Specifically
>>
>> The containers mimic ejb for propagation for a good reason!
>> No session e.g. , new TX, etc
>>
>> Sadly the concurrency utilis only mention @ApplicationScoped, so the
>> Request Context not only doesn't get propagated (which is good), but also
>> doesn't get set up (which is crap).
>>
>> LieGrue,
>> Strub
>>
>> Am 06.03.2016 um 23:03 schrieb John D. Ament <john.d.ament at gmail.com>:
>>
>> I agree, in a sense, with what you're saying. There's nothing in this
>> spec that says it wouldn't be propagated. However, there's nothing in this
>> spec that states clearly that CDI contexts are propagated.
>>
>> If you look at the RI, the RI only seems to propagate transaction state.
>> Considering the age of the spec, I'm not surprised to see that. The worst
>> part is that right now, outside of the ASF, all other EE7 impls seem to be
>> using the RI for concurrency.
>>
>> I'm fairly certain that from this spec's standpoint, the only thing
>> that's actually propagated is the transaction.
>>
>> John
>>
>> On Sun, Mar 6, 2016 at 4:50 PM Reza Rahman <reza_rahman at lycos.com> wrote:
>>
>>> I am re-reading the spec end to end again right now. So far it seems I
>>> have remembered everything correctly.
>>>
>>> You should read over section 2.3. What it is saying is that a container
>>> implementing the Java EE concurrency utilities should ensure whatever
>>> contextual information is needed for managed components to work correctly
>>> should be propagated automatically. For the correct implementation of CDI
>>> scopes, this should also mean any currently active scopes. The section you
>>> are referring to is basically implying that thinking that it is possible to
>>> use these scoped beans in tasks (albeit not reliably since beans could go
>>> out of scope before the thread finishes - for example if the request ends).
>>>
>>> This does not have anything to do with the context service per se. The
>>> context service is an SPI of sorts to allow end user developers to do for
>>> their own applications what the container does behind the scenes for
>>> managed component context propagation.
>>>
>>> I'll read over the entire spec to see if there is anything to contradict
>>> this. If that's not the case what Romain is describing is most likely an
>>> implementation specific bug that did not take into account CDI scope
>>> propagation.
>>>
>>> On Mar 6, 2016, at 4:23 PM, John D. Ament <john.d.ament at gmail.com>
>>> wrote:
>>>
>>> Reza,
>>>
>>> I read through the concurrency utils spec. Was there a specific section
>>> you had in mind? The only references to CDI were near the beginning
>>> warning users to not use Request/Session scoped beans as tasks since the
>>> outer most context may be destroyed before the work is done.
>>>
>>> I have a feeling what you're referring to is the context service:
>>> http://docs.oracle.com/javaee/7/api/javax/enterprise/concurrent/ContextService.html
>>>
>>> If that's the case, then basically this should work OOTB right?
>>>
>>> Task task = new MyTask();
>>> task = contextService.createContextualProxy(task, Task.class);
>>> executor.submit(task);
>>>
>>> // now magically the context should be prop'd?
>>>
>>> Is that about right?
>>>
>>> John
>>>
>>> On Sun, Mar 6, 2016 at 3:30 PM Reza Rahman <reza_rahman at lycos.com>
>>> wrote:
>>>
>>>> Have you actually looked at the EE concurrency spec text in detail?
>>>> What does it say about managed component context propagation?
>>>>
>>>> Without actually doing that further discussing this is just taking
>>>> shots in the dark. As an implementer it should not surprise you that this
>>>> might simply be a bug because the person implementing the concurrency
>>>> utilities for the EE runtime was not told about what to copy over into the
>>>> new thread for CDI to work correctly.
>>>>
>>>> On Mar 6, 2016, at 3:06 PM, Romain Manni-Bucau <rmannibucau at gmail.com>
>>>> wrote:
>>>>
>>>>
>>>> 2016-03-06 20:59 GMT+01:00 Reza Rahman <reza_rahman at lycos.com>:
>>>>
>>>>> 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.
>>>>>
>>>>>
>>>> That's what I wanted/would like. CDI TCK breaks it quite easily and
>>>> @RequestScoped which is *used* today is sadly a @ThreadLocalScoped badly
>>>> named. So to solve it we would need another scope as I mentionned several
>>>> times on this list 100% matching servlet instances lifecycles (on a pure
>>>> CDI side we have the same issue for sessions which are recycled during a
>>>> request, the session scope is corrupted *by spec* in term of user behavior).
>>>>
>>>>
>>>>> 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 <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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>>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
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>>>>>>>>
>>>>>>>>
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>>>>>>>
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>>>>>
>>>>>
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