Memory leak when using @Async after upgrading from 5.1 to 5.2

[arian]

Affects: 5.2.0.RC1

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In our application I upgraded from spring-framework 5.1.9 to 5.2.0.RC1 and our tests started leaking memory.

Previously it looked like this in VisualVM:

And now it looks like this:

I've made a heapdump to see where the memory is going:

I've seen something similar in our application previously, but that was solved by using @MockBean instead of a lot of @ContextConfiguration with @Configuration classes inside our test classes to override beans with mocked objects 🤔...

[sbrannen]

Hi @arian,

Can you possibly reduce this to the smallest application possible that demonstrates the behavior (and provide access to the full example application)?

At the very least, it would be helpful to know what kind of components are active in the ApplicationContext and what configuration (i.e., annotations) you are using in your tests.

Without being able to debug it, we don't really have much to go on.

Thanks in advance!

[arian]

Yes I completely understand! It's difficult to create a reproducible small application for me as I don't really figured out what causes the problem.

At the very least, it would be helpful to know what kind of components are active in the ApplicationContext and what configuration (i.e., annotations) you are using in your tests.

Is there an easy way to print a log of this or something?

Anyway I'll try to do some more testing after the weekend and see if I can report back!

[sbrannen]

Is there an easy way to print a log of this or something?

Not for the annotations is use; however, it appears that you're using @Async. So perhaps focusing on that part of your application might reveal something.

If you're using Spring Boot, you could use the actuator endpoint to get a list of all beans in the ApplicationContext. Otherwise, you might try Spring's LiveBeansView support.

Anyway I'll try to do some more testing after the weekend and see if I can report back!

Thanks.

[arian]

The problem seems to occur with @EnableAsync. Without it running some tests look like:

With @EnableAsync

Also a heapdump when running without @EnableAsync doesn't show the list with org.springframework.scheduling.annotation.AnnotationAsyncExecutionInterceptor objects in memory.

Also commenting out all @Async seem to run the tests ok too.

Checked with 5.2.0.RC2, same result as RC1.

[sbrannen]

Thanks for investigating further and providing us the detailed feedback!

We'll look into it.

[sbrannen]

Tentatively slated for 5.2 GA for further investigation since this appears to be a regression.

[sbrannen]

Hi @arian,

Since this appears to be a regression, we'd really like to get to the bottom of this before we release Spring Framework 5.2 GA next week.

We brainstormed a bit within the team about possible causes for this, but we're really just shooting in the dark without being able to debug a project that reproduces the memory leak.

Based on your knowledge that the issue involves the use of @Async, we would be very grateful if you could provide us a small application that reproduces the problem.

If that's not possible, can you please run your test suite against 5.2 M1, 5.2 M2, and 5.2 M3 and let us know for which milestone versions you experience the problem?

That would help us at least to pinpoint when the regression was introduced.

Thanks in advance!

[sbrannen]

@arian, don't worry about the requests in my previous comment.

The following test class seems to reproduce the problem, if you limit the max heap size to 64 MB.

The test class succeeds unless you uncomment @DirtiesContext, in which case it leads to java.lang.OutOfMemoryError: GC overhead limit exceeded.

@SpringJUnitConfig
class AsyncTestCase {

	@RepeatedTest(1000)
	// @DirtiesContext
	void test() {
	}

	@Configuration
	@EnableAsync
	@Import(AsyncService.class)
	static class Config {
	}

	static class AsyncService {

		@Async
		void doSomething() {
		}
	}
}

[sbrannen]

@arian, one last question:

Which testing framework are you using?

• JUnit 4
• JUnit Jupiter
• TestNG
• ?

[arian]

Cool, I was just looking into a way to reproduce it!

We're still using junit 4 at the moment.

[sbrannen]

Cool, I was just looking into a way to reproduce it!

We're still using junit 4 at the moment.

OK. Thanks for the feedback.

[sbrannen]

Same error occurs with JUnit 4:

@RunWith(SpringRunner.class)
public class AsyncTestCase {

	@Test
	@Repeat(1000)
	@DirtiesContext
	public void test() {
	}

	@Configuration
	@EnableAsync
	@Import(AsyncService.class)
	static class Config {
	}

	static class AsyncService {

		@Async
		void doSomething() {
		}
	}
}

[sbrannen]

@arian, can you confirm that executing your test suite with -Dcglib.useCache=false works without a memory leak?

[sbrannen]

Mystery solved: the newly introduced AnnotationMatchingPointcut.AnnotationCandidateClassFilter class doesn't implement equals().

I've got a fix locally that I'll apply tomorrow to master.

[arian]

@arian, can you confirm that executing your test suite with -Dcglib.useCache=false works without a memory leak?

With that it seems to work without leaks.

Mystery solved

Great!