EntityManager issue in multithreaded tests

[amasson88]

Describe the bug

Injected test EntityManager during JUnit tests seems to be shared across threads which causes random errors.

To Reproduce
Steps to reproduce the behavior:

1. In a test, use EntityManager to write in DB (same jpa unit) in app CDI classes, from at least 2 different threads
2. Several errors are possible, example:

java.lang.IllegalStateException: org.hibernate.TransientPropertyValueException: object references an unsaved transient instance

Expected behavior

EntityManager instances should be per unit and per thread, like in a CDI app server (request scoped?)
not just per persistent unit

Additional context

JDK 17 / linux and macos

[guhilling]

Maybe I can take a look in a few days. But I'm afraid that'll be hard to fix. Would you have a small test project so I can reproduce that easily?

[amasson88]

thanks, yes, I can try to write a small standalone test

meanwhile here is a quick hack I tested that seems to work in my scenario (except that it breaks one of the cdi-test test, see the disabled one, not sure why...)

hack_for_multithread_EntityManager.patch

(but there should be a better way to make a proxy of the EntityManager than the manual delegate I implemented)

[amasson88]

@guhilling see https://github.com/amasson88/cdi-test/pull/1/files

[guhilling]

Yes! I also created a branch for this issue 👍

[guhilling]

Would you have a link to a document that defines the expected behaviour?

[amasson88]

https://jakarta.ee/specifications/persistence/3.0/jakarta-persistence-spec-3.0.html#a11805 ?

[guhilling]

Ah, I get it. Now I forgot the original issue. Sorry. Need some time to think it through.