ebean: Datasource connection deadlock

Expected behavior

It is hoped that the new query caused by the previous query process should use the same jdbc connection.

Actual behavior

When the previous jdbc connection is not closed, hashcode triggers lazy loading and re-acquires a new jdbc connection, which may cause mutual exclusion of connections and deadlock in concurrent situations. For example, the maximum available connection pool is 2, when two threads trigger lazy loading at the same time, because the previous two connections are not released and get new connections through the connection pool, the connection pool finds that there is no available connection and suspends the thread to wait for other threads to release the connection, and both threads are stuck in getting new connections, resulting in deadlock.

Steps to reproduce

java.lang.RuntimeException
	at test.system.Ebean$TConnection.invoke(Ebean.java:369)
	at jdk.proxy2/jdk.proxy2.$Proxy161.getAutoCommit(Unknown Source)
	at io.ebeaninternal.server.transaction.JdbcTransaction.checkAutoCommit(JdbcTransaction.java:282)
	at io.ebeaninternal.server.transaction.JdbcTransaction.<init>(JdbcTransaction.java:223)
	at io.ebeaninternal.server.transaction.TransactionManager.createTransaction(TransactionManager.java:397)
	at io.ebeaninternal.server.transaction.TransactionFactoryBasic.create(TransactionFactoryBasic.java:55)
	at io.ebeaninternal.server.transaction.TransactionFactoryBasic.createReadOnlyTransaction(TransactionFactoryBasic.java:29)
	at io.ebeaninternal.server.transaction.TransactionManager.createReadOnlyTransaction(TransactionManager.java:390)
	at io.ebeaninternal.server.core.DefaultServer.createReadOnlyTransaction(DefaultServer.java:2231)
	at io.ebeaninternal.server.core.OrmQueryRequest.initTransIfRequired(OrmQueryRequest.java:278)
	at io.ebeaninternal.server.core.DefaultServer.findList(DefaultServer.java:1535)
	at io.ebeaninternal.server.core.DefaultServer.findList(DefaultServer.java:1515)
	at io.ebeaninternal.server.core.DefaultBeanLoader.executeQuery(DefaultBeanLoader.java:180)
	at io.ebeaninternal.server.core.DefaultBeanLoader.loadBean(DefaultBeanLoader.java:163)
	at io.ebeaninternal.server.core.DefaultServer.loadBean(DefaultServer.java:561)
	at io.ebeaninternal.server.loadcontext.DLoadBeanContext$LoadBuffer.loadBean(DLoadBeanContext.java:208)
	at io.ebean.bean.EntityBeanIntercept.loadBeanInternal(EntityBeanIntercept.java:852)
	at io.ebean.bean.EntityBeanIntercept.loadBean(EntityBeanIntercept.java:829)
	at io.ebean.bean.EntityBeanIntercept.preGetter(EntityBeanIntercept.java:923)
	at test.domain.entity.Root._ebean_get_reference(Root.java:6)
	at test.domain.entity.Root.hashCode(Root.java:657)
	at java.base/java.util.HashMap.hash(HashMap.java:338)
	at java.base/java.util.HashMap.put(HashMap.java:610)
	at java.base/java.util.HashSet.add(HashSet.java:221)
	at io.ebean.common.BeanSet.internalAdd(BeanSet.java:84)
	at io.ebean.common.BeanSet.internalAddWithCheck(BeanSet.java:74)
	at io.ebeaninternal.server.deploy.BaseCollectionHelp.add(BaseCollectionHelp.java:39)
	at io.ebeaninternal.server.deploy.BeanSetHelp.add(BeanSetHelp.java:19)
	at io.ebeaninternal.server.deploy.BeanPropertyAssocMany.addBeanToCollectionWithCreate(BeanPropertyAssocMany.java:271)
	at io.ebeaninternal.server.query.CQuery.setLazyLoadedChildBean(CQuery.java:417)
	at io.ebeaninternal.server.query.SqlTreeNodeBean$Load.complete(SqlTreeNodeBean.java:421)
	at io.ebeaninternal.server.query.SqlTreeNodeBean$Load.perform(SqlTreeNodeBean.java:447)
	at io.ebeaninternal.server.query.SqlTreeNodeBean.load(SqlTreeNodeBean.java:464)
	at io.ebeaninternal.server.query.SqlTreeNodeRoot.load(SqlTreeNodeRoot.java:45)
	at io.ebeaninternal.server.query.CQuery.readNextBean(CQuery.java:447)
	at io.ebeaninternal.server.query.CQuery.hasNext(CQuery.java:531)
	at io.ebeaninternal.server.query.CQuery.readCollection(CQuery.java:564)
	at io.ebeaninternal.server.query.CQueryEngine.findMany(CQueryEngine.java:379)
	at io.ebeaninternal.server.query.DefaultOrmQueryEngine.findMany(DefaultOrmQueryEngine.java:131)
	at io.ebeaninternal.server.core.OrmQueryRequest.findList(OrmQueryRequest.java:470)
	at io.ebeaninternal.server.core.DefaultServer.findList(DefaultServer.java:1536)
	at io.ebeaninternal.server.core.DefaultServer.findList(DefaultServer.java:1515)
	at io.ebeaninternal.server.core.DefaultBeanLoader.executeQuery(DefaultBeanLoader.java:180)
	at io.ebeaninternal.server.core.DefaultBeanLoader.loadMany(DefaultBeanLoader.java:45)
	at io.ebeaninternal.server.core.DefaultServer.loadMany(DefaultServer.java:546)
	at io.ebeaninternal.server.loadcontext.DLoadManyContext$LoadBuffer.loadMany(DLoadManyContext.java:228)
	at io.ebean.common.AbstractBeanCollection.lazyLoadCollection(AbstractBeanCollection.java:101)
	at io.ebean.common.BeanSet.init(BeanSet.java:137)
	at io.ebean.common.BeanSet.iterator(BeanSet.java:283)
	at java.base/java.util.Spliterators$IteratorSpliterator.estimateSize(Spliterators.java:1865)
	at java.base/java.util.Spliterator.getExactSizeIfKnown(Spliterator.java:414)
	at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:508)
	at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499)
	at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:921)
	at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:682)
	at test.domain.entity.Student.getCuDetail(Student.java:634)
	at test.domain.entity.Student.getCuDetail(Student.java:627)
	at test.dto.response.StudentRespDTO.<init>(StudentRespDTO.java:79)
	at test.repository.StudentUnavailabilityTimeRepositoryTest.lambda$test$1(StudentUnavailabilityTimeRepositoryTest.java:145)
	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:539)
	at java.base/java.util.concurrent.FutureTask.run$$$capture(FutureTask.java:264)
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
	at java.base/java.lang.Thread.run(Thread.java:833)

About this issue

Original URL
State: closed
Created 10 months ago
Comments: 19 (9 by maintainers)

Commits related to this issue

#3173 - BeanSet lazy loading / Too many DataSource connections used - The error reported was that a DataSource connection pool maxed out - The symptom was that there was an additional lazy loading qu... — committed to ebean-orm/ebean by rbygrave 10 months ago
Merge pull request #3203 from ebean-orm/feature/3173-BeanSet #3173 - BeanSet lazy loading / Too many DataSource connections used — committed to ebean-orm/ebean by rbygrave 10 months ago
Follow up #3173 - Add test for BeanSet lazy loading OneToMany with hashCode/equals — committed to ebean-orm/ebean by rbygrave 10 months ago
Follow up #3173 - Add test for BeanSet clear() when hashCode/equals used This shows the extra lazy loading that is occurring when clear() is called on the [Bean]Set DUE to the hashcode/equals impleme... — committed to ebean-orm/ebean by rbygrave 10 months ago
Merge pull request #3204 from ebean-orm/feature/3173-beanSet-clear Follow up #3173 - Add test for BeanSet clear() when hashCode/equals used — committed to ebean-orm/ebean by rbygrave 10 months ago
Follow up #3173 - Change BeanSet clear() to lazy load ALL properties To avoid the 1+N lazy loading queries that are invoked due to the clear() when the entity bean in the Set has a hashCode/equals im... — committed to ebean-orm/ebean by rbygrave 10 months ago
Merge pull request #3205 from ebean-orm/feature/3173-beanSet-clear Follow up #3173 - Change BeanSet clear() to lazy load ALL properties — committed to ebean-orm/ebean by rbygrave 10 months ago
[12x] Backport of fix for #3173 BeanSet init(), initClear() and BeanMap - BeanSet init() and initClear() load with onlyIds false because the expectation is that with BeanSet the equals/hashCode imple... — committed to ebean-orm/ebean by rbygrave 10 months ago
Merge pull request #3218 from ebean-orm/backport-12x/3173-BeanSet-init-loading [12x] Backport of fix for #3173 BeanSet init(), initClear() and BeanMap — committed to ebean-orm/ebean by rbygrave 10 months ago

Most upvoted comments

ebean version 12.16.2 has been released with the back ported patch https://github.com/ebean-orm/ebean/pull/3218

Note: The branch maintain-v12 is the maintenance branch for 12.x releases going forward.

rbygrave on Sep 7, 2023

I have completed the test code but I don’t have permission to push it up. What should I do?

Did you “create a fork”?

You won’t have permission to push to the repo directly but if you have your own fork you should be able to push to that.

Thank you, I have submitted the test code to this address: https://github.com/lbsoft-lwsoft/example-minimal/blob/test-case-3173/src/test/java/org/example/domain/ConnectionLeakTest.java

lbsoft-lwsoft on Aug 28, 2023

I think we posted at the same time there.

solve this problem directly at the bottom layer

Yes, it looks like we can fix it in OrmQueryRequest in initTransIfRequired() and endTransIfRequired() for the read-only case.

rbygrave on Aug 21, 2023