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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

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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.

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.