Spring Data Rest gives GC overhead exceeded

Question

EDITED

There are 2 entities User and RefSecQuestion linked as below -

Inside User : This was changed to EAGER to Work around Bug

@ManyToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "question", nullable = false)
    public RefSecQuestion getRefSecQuestion() {
        return this.refSecQuestion;
}

Inside RefSecQuestion :

@OneToMany(fetch = FetchType.LAZY, mappedBy = "refSecQuestion")
public Set<User> getUsers() {
    return this.users;
} 

Visiting URL - /api/refSecQuestions or /api/users/2/refSecQuestions give this error -

 11:25:14,320 WARN LoadContexts.cleanup():115 - HHH000100: Fail-safe cleanup (collections) : org.hibernate.engine.loading.internal.CollectionLoadContext@32f6b537<rs=org.apache.commons.dbcp2.DelegatingResultSet@72b935ef>
2014-10-19 11:25:14.522:WARN:oejs.ServletHandler:qtp1075697729-17: 
org.springframework.web.util.NestedServletException: Handler processing failed; nested exception is java.lang.OutOfMemoryError: GC overhead limit exceeded
    at org.springframework.web.servlet.DispatcherServlet.triggerAfterCompletionWithError(DispatcherServlet.java:1280)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:958)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:870)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:687)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
    at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:769)
    at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:585)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)
    at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:577)
    at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:223)
    at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1125)
    at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:515)
    at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185)
    at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1059)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
    at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:215)
    at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:110)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)
    at org.eclipse.jetty.server.Server.handle(Server.java:497)
    at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:311)
    at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:248)
    at org.eclipse.jetty.io.AbstractConnection$2.run(AbstractConnection.java:540)
    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:610)
    at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:539)
    at java.lang.Thread.run(Thread.java:745)
Caused by: 
java.lang.OutOfMemoryError: GC overhead limit exceeded
    at org.hibernate.internal.AbstractSessionImpl.generateEntityKey(AbstractSessionImpl.java:327)
    at org.hibernate.engine.internal.StatefulPersistenceContext.getCollectionOwner(StatefulPersistenceContext.java:694)
    at org.hibernate.loader.plan.exec.process.internal.CollectionReferenceInitializerImpl.findCollectionOwner(CollectionReferenceInitializerImpl.java:141)
    at org.hibernate.loader.plan.exec.process.internal.CollectionReferenceInitializerImpl.finishUpRow(CollectionReferenceInitializerImpl.java:87)
    at org.hibernate.loader.plan.exec.process.internal.AbstractRowReader.readRow(AbstractRowReader.java:125)
    at org.hibernate.loader.plan.exec.process.internal.ResultSetProcessorImpl.extractResults(ResultSetProcessorImpl.java:129)
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:138)
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:102)
    at org.hibernate.loader.collection.plan.AbstractLoadPlanBasedCollectionInitializer.initialize(AbstractLoadPlanBasedCollectionInitializer.java:100)
    at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:693)
    at org.hibernate.event.internal.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:92)
    at org.hibernate.internal.SessionImpl.initializeCollection(SessionImpl.java:1897)
    at org.hibernate.collection.internal.AbstractPersistentCollection$4.doWork(AbstractPersistentCollection.java:558)
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:260)
    at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:554)
    at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:142)
    at org.hibernate.collection.internal.AbstractPersistentCollection$1.doWork(AbstractPersistentCollection.java:171)
    at org.hibernate.collection.internal.AbstractPersistentCollection$1.doWork(AbstractPersistentCollection.java:156)
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:260)
    at org.hibernate.collection.internal.AbstractPersistentCollection.readSize(AbstractPersistentCollection.java:155)
    at org.hibernate.collection.internal.PersistentSet.isEmpty(PersistentSet.java:166)
    at org.springframework.data.rest.webmvc.PersistentEntityResourceAssembler$1.doWithAssociation(PersistentEntityResourceAssembler.java:159)
    at org.springframework.data.mapping.model.BasicPersistentEntity.doWithAssociations(BasicPersistentEntity.java:337)
    at org.springframework.data.rest.webmvc.PersistentEntityResourceAssembler.getEmbeddedResources(PersistentEntityResourceAssembler.java:128)
    at org.springframework.data.rest.webmvc.PersistentEntityResourceAssembler.wrap(PersistentEntityResourceAssembler.java:106)
    at org.springframework.data.rest.webmvc.PersistentEntityResourceAssembler.toResource(PersistentEntityResourceAssembler.java:84)
    at org.springframework.data.rest.webmvc.RepositoryPropertyReferenceController$1.apply(RepositoryPropertyReferenceController.java:141)
    at org.springframework.data.rest.webmvc.RepositoryPropertyReferenceController$1.apply(RepositoryPropertyReferenceController.java:110)
    at org.springframework.data.rest.webmvc.RepositoryPropertyReferenceController.doWithReferencedProperty(RepositoryPropertyReferenceController.java:464)
    at org.springframework.data.rest.webmvc.RepositoryPropertyReferenceController.followPropertyReference(RepositoryPropertyReferenceController.java:148)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

Answer 1

GC overhead limit exceeded means you run out of memory when using the CMS garbage collector. This can either be due to a memory leak or your application simply having a larger live dataset than your VM options allow. To figure out the issue use

-XX:+HeapDumpOnOutOfMemoryError

and possibly -XX:HeapDumpPath (check Java HotSpot VM Options for more information). Then run a tool like Eclipse MAT to figure out what the issue is. There are also several commercial tools available like Plumbr.