I just want to bring this to everyone attention one more time.

The conversation scope concurrency control mechanism seems to be a frequent point of pain in many projects.

Especially when working with browser triggered asynchronous requests, you can not rely on client-sided request synchronization.

Weld, unlike OWB, grants a 1 second timeout prior to throwing a (the specified) BusyConversationException mitigating the effect a bit.

This is a rather strict un-configurable type of CC. Also its completely out of alignment with the other build-in scopes, offering no CC what so ever.

In the cases of Session- and Application-Scope, thread handling is left entirely to the developer, even so they are just as vulnerable in AJAX environments.

We should really consider introducing a common configurable mechanism, that is aligned across all scopes (obviously accounting for backwards compatibility in the case of conversation scope).

Would really appreciate some feedback.

Kind regards,

Stephan

On Mon, 22 Feb 2016 at 23:10 Reza Rahman <Reza.Rahman@oracle.com> wrote:

We've discussed this issue before. I definitely still think @Lock belongs in a modular CDI specification. It would be highly useful to both @Singleton and @ApplicationScoped. Today if I need to use declarative concurrency control for a shared component I am essentially forced to use EJB singleton - which shouldn't be the case and perhaps should not have been the case past Java EE 6.

On 2/19/2016 5:27 AM, Stephan Knitelius wrote:

Hi all,

CDI spec does not define a common concurrency control mechanism. The time any type of concurrency control is mentioned is in conjunction with EJB and a rather restrictive one for conversation context.

CDI Spec:

The container ensures that a long-running conversation may be associated with at most one request at a time, by blocking or rejecting concurrent requests. If the container rejects a request, it must associate the request with a new transient conversation and throw an exception of typejavax.enterprise.context.BusyConversationException.

It would be helpful if a common configurable concurrency mechanism (EJB Singleton style locking?) could be established for all normal scopes.

What are your thoughts on this?

Regards,

Stephan

______________________________________
Stephan Knitelius
Alteburger Str. 274
50968 Köln / Cologne
Deutschland / Germany
stephan@knitelius.com
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