Suspected memory leak in SpringApplicationShutdownHook during spring boot testsuite execution

[Mobe91]

Spring Boot version: 3.1.2
Java version: 17.0.3, vendor: Eclipse Adoptium

Executing a spring-boot testsuite a java.lang.OutOfMemoryError is thrown after some time.

The testsuite is executed via maven-surefire-plugin:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-surefire-plugin</artifactId>
    <version>3.1.2</version>
    <configuration>
        <forkCount>1</forkCount>
        <argLine>-Xmx2g -XX:+HeapDumpOnOutOfMemoryError --add-opens java.base/java.lang=ALL-UNNAMED</argLine>
    </configuration>
</plugin>

The test context caching has been limited to 1 by creating a spring.properties file with the following content:

spring.test.context.cache.maxSize=1

It has been verified that above setting takes effect by enabling DEBUG logging for org.springframework.test.context.cache.

From the above setup I would expect that only the last used application context is cached and all other application contexts become eligible for garbage collection.

However, when examining the heap dump that is created when the java.lang.OutOfMemoryError is thrown (compare -XX:+HeapDumpOnOutOfMemoryError setting above) I see that SpringApplicationShutdownHook#closedContexts contains 36 entries retaining around 1.6 GB of heap space. When analyzing the path to GC roots using Eclipse MAT for the application contexts contained in this Map then the only path to a GC root goes through the WeakHashMap$Entry holding the respective application context. When instructing Eclipse MAT to show paths to GC roots excluding weak references no paths are output.

Given that a full GC should happen before a java.lang.OutOfMemoryError is thrown it seems like something is blocking the GC of application contexts in SpringApplicationShutdownHook#closedContexts.

I can probably provide the heap dump if required (would need to check, though).

[bclozel]

While this issue occurs while running tests, I think this is a duplicate of #37096
We will reopen it if it turns out the use case is different. @Mobe91 please subscribe to the other issue so that you can confirm when the fix is in. Thanks!

[Mobe91]

@bclozel
I'd like to re-open this issue because the workaround described in for #37096 (logging.register-shutdown-hook=false) does not solve this. I verified by debugging that no shutdown hook is registered in org.springframework.boot.context.logging.LoggingApplicationListener#registerShutdownHookIfNecessary. Yet, the same java.lang.OutOfMemoryError can be observed as described initially. Therefore I think this is a different issue.

I can see that the ApplicationContext is registered with the shutdown hook in org.springframework.boot.SpringApplication#refreshContext.

[wilkinsona]

@Mobe91 Can you please provide a minimal sample that reproduces the leak?

[Mobe91]

@wilkinsona I could try but I think it would take quite some effort. Do you think it would make sense for you to first look at the dump? Maybe you spot something quickly that I couldn't...