Upgrade from 3.3.x to 3.4.x and 4.0.0: SpringBootTests throw OutOfMemoryError

[Christian-Harnisch-DB]

• In our test setup code, we have a ContextConfiguration which adds beans to the application context (MockWebServer and GreenMail instances, which are shut down on ContextClosedEvent by calling their stop() and shutdown() methods)
• The SpringBootTests additionally use the following annotations: @DirtiesContext(classMode = AFTER_EACH_TEST_METHOD) and @TestInstance(PER_METHOD)
• With Spring Boot 3.3.5 the tests execute successfully
• With 3.4.1 and 3.4.2 and 4.0.0 the tests fail with an out of memory exception (java.lang.OutOfMemoryError: Java heap space)
• When profiling the test runs, we observe that over 400 instances of org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext are referenced from org.springframework.beans.factory.support.DefaultListableBeanFactory. It appears that this is about one instance per SpringBootTest.
• With 3.3.5, the profiler (YourKit) marks them as [Weak/Soft Reachable], whereas in 3.4.1 it doesn't (are they strong references now?)
• We are not sure if there is a new leak, or if existed before and only now exhausts heap space

Example stacktrace:

Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'xyz' defined in class path resource [abc.class]: Unexpected exception during bean creation
	at app//org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:536)
	at app//org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:336)
	at app//org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:289)
	at app//org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:334)
	at app//org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199)
	at app//org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:254)
	at app//org.springframework.beans.factory.support.DefaultListableBeanFactory.addCandidateEntry(DefaultListableBeanFactory.java:1883)
	at app//org.springframework.beans.factory.support.DefaultListableBeanFactory.findAutowireCandidates(DefaultListableBeanFactory.java:1847)
	at app//org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveMultipleBeanCollection(DefaultListableBeanFactory.java:1737)
	at app//org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveMultipleBeans(DefaultListableBeanFactory.java:1705)
	at app//org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1580)
	at app//org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1519)
	at app//org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:913)
	at app//org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:791)
	... 100 more
Caused by: java.lang.OutOfMemoryError: Java heap space

Environment:

• JDK Version: OpenJDK Runtime Environment Temurin-21.0.5+11 (build 21.0.5+11-LTS)
• Operating System: Windows 11
• Spring Boot Version: 3.4.1 (issue occurs), 3.3.5 (no issue)
• Build system: Gradle Wrapper 8.12

Attempted solutions:

• Set server.shutdown to immediate
• Tried jetty and undertow instead of tomcat

Additional information:

• We observe the same behaviour error with 3.4.2 and 4.0.0 (originally tested with 3.4.1)
• 3.3.x shows basically the same increase in heap memory usage over time like in this screenshot of our profiler. However, 3.3.x doesn't trigger the out of memory error.

[snicoll]

When profiling the test runs, we observe that over 400 instances of

That looks odd to me as the cache has a default size of 32. Did you increase the size (using spring.test.context.cache.maxSize or by creating your own?)

[Christian-Harnisch-DB]

That looks odd to me as the cache has a default size of 32. Did you increase the size (using spring.test.context.cache.maxSize or by creating your own?)

No, we neither increased the cache size nor created our own.

[sbrannen]

Thanks for the feedback, @Christian-Harnisch-DB.

Though without a means to observe the behavior you're describing, it will be very difficult for us to determine the cause.

In light of that, please provide us a minimal sample application (or all-in-one test class) that reproduces the issue, preferably something that we can download and run ourselves (such as public Git repository or a ZIP file attached to this issue).

Thanks in advance!

[spring-projects-issues]

If you would like us to look at this issue, please provide the requested information. If the information is not provided within the next 7 days this issue will be closed.

[Christian-Harnisch-DB]

Sorry for the delay, I'm sort of confused by this memory leak.

I uploaded a demo project in the attached ZIP file. This is freshly generated using Spring Initializr, I only added that DemoApplicationTests.contextLoads() runs numerous times instead of once. If you let it run for some minutes, you should see the heap usage grow over time like in the attached screenshot.

In our actual code, we don't need that many test runs. I think this is because the demo contains no additional code, so it's just standard Spring beans occupying memory. I'm not sure, though.

memleakdemo.zip