[wildfly-dev] Making Jandex annotation index available to components

[Scott Marlow]

On 10/27/2016 08:42 AM, Gunnar Morling wrote:
> Hi,
>
> ---
> TL,DR: Hibernate components would like to receive the Jandex index 
> during deployment. A new method IndexView#close() may help to address 
> concerns about long-living index view references
> ---
>
> Different projects from the Hibernate umbrella (e.g. ORM, Validator 
> and Search) rely heavily on meta-data given via annotations. In order 
> to speed up annotation retrieval, we are looking into using the Jandex 
> index created for deployments by the container.
>
> This would require subsystems like JipiJapa or the one for Bean 
> Validation to pass the IndexView for the deployment to the 
> bootstrapped component. The change itself should be easy, I hope. But 
> Scott expressed concerns about components keeping references to the 
> index after the deployment phase has succeeded. As indexes can be 
> large, this may potentially block a big chunk of memory for as long as 
> the deployment is running.
>
> Of course we can promise that Hibernate components wouldn't keep such 
> references ;) But if that's not enough, could this concern be 
> mitigated by adding a new method IndexView#close()?
>
> This method would free all resources of the index and would be called 
> by the container after the deployment has finished. Any operation on a 
> closed index view would throw an exception indicating that the view 
> has been closed. Then, even if a component accidentally kept a 
> reference to an IndexView, it wouldn't retain much memory (of course 
> the index view wouldn't be of much use to the component in that state).
>
> Would that be an acceptable way forward? If so, I could send a pull 
> request towards Jandex. In a next step WF would have to make use of 
> that new version and invoke close() on a deployment's index at a 
> suitable time during the deployment lifecycle and eventually pass the 
> index to ORM et al.
>
> In a subsequent step we may consider to address use cases such as 
> dynamic reconfiguration which would require to access the index 
> *after* deployment time. One way for addressing this may be to allow 
> for passing in some kind of executor which would expect e.g. a Lambda 
> doing work on an IndexView passed in by the executor. That way 
> components could access the index at runtime, while not keeping a 
> reference to it themselves and thus allowing the container to manage 
> the index and e.g. close or re-open it upon execution. But I think 
> this could be done as a follow-up.

A related question might be if creating a Jandex Index after application 
deployment completes, could be backed by the application classloader 
defined classes and whether that would be memory space efficient enough 
for runtime use.

>
> Any thoughts?
>
> Thanks,
>
> --Gunnar
>
> PS: As a side note, Hibernate Validator currently reads annotations 
> lazily at runtime (when first validating a specific bean type). When 
> using Jandex, we'd have to change this to eagerly build up all the 
> meta-data for the types listed in the index passed during bootstrap. A 
> bit of work, but as said we hope to gain a nice performance 
> improvement from it.
>
>
>
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