method annotated with @Transactional(isolation = Isolation.READ_COMMITTED) returns uncommitted data

[jvanheesch]

Reproducer kan be found here: https://github.com/jvanheesch/spring-boot-isolation

[schauder]

Please simplify the reproducer, so it can be run locally without all that Docker overhead.

You shouldn't need a web application either.
A simple integration test should do.

[jvanheesch]

I worked out an example without docker and web: https://github.com/jvanheesch/spring-boot-isolation/tree/SpringBootTest

[schauder]

The reproducer is broken.
In the first example you call Thread.start() https://github.com/jvanheesch/spring-boot-isolation/blob/SpringBootTest/src/test/java/io/github/jvanheesch/ExampleIT.java#L15

In the second example you call Thread.run() https://github.com/jvanheesch/spring-boot-isolation/blob/SpringBootTest/src/test/java/io/github/jvanheesch/ExampleIT.java#L26
This does NOT start a new thread, but runs the closure in the current thread. So everything else runs after the update is performed and committed.

The call to readUncommited is irrelevant.

You really shouldn't use Thread.sleep(millis) to weave your threads for such tests. Instead I recommend to use CountDownLatch

[jvanheesch]

Using Thread.run() instead of Thread.start() was a sloppy and obvious mistake on my part. I've updated the reproducer and hope it can be reconsidered again.

[schauder]

Ok, that is strange.

I massaged the tests a little to use CountDownLatch for synchronization.
And also added a test to demonstrate the behaviour with just JDBC, which behaves as expected.

https://github.com/schauder/issue-jpa-2733-spring-boot-isolation/tree/SpringBootTest