[cdi-dev] Enhancing SPI to support async operation for contexts

[Jozef Hartinger]

+1

On 02/19/2015 05:40 PM, Mark Struberg wrote:
> Even in Servlets-3.0 a ‚Request‘ is only attached to exactly one single thread AT THE SAME TIME afaik.
>
> So they can switch a Request from one thread to another one, but there is always just a single one accessing it at the same time. At least that is what I did understand.
>
> LieGrue,
> strub
>
>
>> Am 19.02.2015 um 17:33 schrieb Sven Linstaedt <sven.linstaedt at gmail.com>:
>>
>> Hi,
>>
>> and sorry for spontaneously dropping in. Just to clarify some personal questions/assumptions:
>>
>> 1. Regarding threading the current spec only states that "A context may be associated with one or more threads".
>>
>> 2. It is nowhere stated that @RequestScoped beans are inherently thread safe. Thread safety was implied from the servlet spec, because the scope backing container (ServletRequest#attributes) was executed single threaded.
>>
>> 3. With Servlet 3.0 the same ServletRequest#attributes is available for access from multiple threads via  ServletRequest#startAsync(), so containing objects may have a need for synchronization.
>>
>> 4. Why does CDI 2.0 has to care about thread safety of @RequestScoped beans? If the application is for some reason setting the request in async mode, the application must also ensure, it's containing and accessed beans are thread safe.
>>
>>
>> Best regards
>> Sven
>>
>> 2015-02-19 11:22 GMT+01:00 Romain Manni-Bucau <rmannibucau at gmail.com>:
>> Hi
>>
>> I'm +1 for it but it needs important changes (= surely new contexts).
>> Typically we can't change today @RequestScoped (which has no link with
>> a request but only with a thread!).
>>
>> So we could have @RequestScoped (~ @ThreadLocalScoped) and
>> @InheritedRequestScoped which would be a real request scope (but not
>> an InheritedThreadLocal please)
>>
>> For the request it makes a lot of sense since you need to stay thread
>> safe even accross threads (servlet spec) and avoids to be forced to
>> use message passing which - even if a good pattern - adds boilerplate
>> code for simple async needs.
>>
>> For JAXRS I dont know since it is really suspend/resume semantic so
>> request scope maybe doesnt makes much sense here (there is a break in
>> the flow).
>>
>>
>>
>> Romain Manni-Bucau
>> @rmannibucau
>> http://www.tomitribe.com
>> http://rmannibucau.wordpress.com
>> https://github.com/rmannibucau
>>
>>
>> 2015-02-19 10:32 GMT+01:00 Antoine Sabot-Durand <antoine at sabot-durand.net>:
>>> Hi All,
>>>
>>> Beyond the asynchronous event case, shouldn’t we provide a way for user to launch async treatments in CDI with the possibility to keep the existing contexts at the moment of async operation launch?
>>> Today servlet or JAX-RS spec support async call without the loss of request for instance. Shouldn’t we think to something like that?
>>>
>>> Thanks for your input on that point.
>>>
>>> Antoine
>>>
>>>
>>>
>>>
>>>
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>
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