Spring Boot JPA; JpaRepository return Stream<T>; logAbandoned: true shows that Connection is abandoned.

I did a small proof of concept with Spring Boot JPA, that has JpaRepository which has one custom method, that returns a Stream of entities. I turned on a bit of logging and currently it seems that though the Stream reading works well, then the database connection is abandoned. That concerns me a bit. Should I be worried and is this maybe a leakage?

application.yml:

spring:
  datasource:
    removeAbandonedTimeout: 30
    remove-abandoned: true
    log-abandoned: true

Code:

package my.test;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;

import java.util.stream.Stream;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@SpringBootApplication
@EnableScheduling
public class StreamErrorAppRunner {

    public static void main(String[] args) {
        SpringApplication.run(StreamErrorAppRunner.class);
    }

    @Bean
    public CommandLineRunner demo(TestEntityRepository testEntityRepository) {
        return (args) -> {
            testEntityRepository.save(new TestEntity("test_one"));
            testEntityRepository.save(new TestEntity("test_two"));
            testEntityRepository.save(new TestEntity("test_three"));
            testEntityRepository.save(new TestEntity("test_four"));
            testEntityRepository.save(new TestEntity("test_five"));
            testEntityRepository.save(new TestEntity("test_six"));
            testEntityRepository.save(new TestEntity("test_seven"));
        };
    }

}

@Component
class TestEntityLogger {
    private static final Logger logger = LoggerFactory.getLogger(TestEntityLogger.class);

    private final TestEntityRepository testEntityRepository;

    @Autowired
    TestEntityLogger(TestEntityRepository testEntityRepository) {
        this.testEntityRepository = testEntityRepository;
    }

    @Scheduled(fixedDelay = 60000, initialDelay = 5000)
    public void logAllTestEntities() {
        try (Stream<TestEntity> entities = testEntityRepository.findEntities()) {
            entities.forEach(e -> logger.info(e.toString()));
        }
        logger.info("Finished reading the stream. It should be closed by now.");
    }
}

@Entity
class TestEntity {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;
    private String name;

    public TestEntity() {
    }

    public TestEntity(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "TestEntity{" +
                "id=" + id +
                ", name='" + name + '\'' +
                '}';
    }
}

interface TestEntityRepository extends JpaRepository<TestEntity, Long> {

    @Query("select t from TestEntity t")
    Stream<TestEntity> findEntities();

}

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://maven.apache.org/POM/4.0.0"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <artifactId>sb-jpa-stream-bug-poc</artifactId>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
    <groupId>my.test.app</groupId>
    <version>1.0-SNAPSHOT</version>

    <modelVersion>4.0.0</modelVersion>

    <dependencies>
        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <version>1.4.192</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>1.3.5.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>
</project>

Relevant logs:

2016-06-20 10:46:18.115  INFO 10436 --- [           main] my.test.StreamErrorAppRunner             : Started StreamErrorAppRunner in 2.401 seconds (JVM running for 2.683)
2016-06-20 10:46:23.090  INFO 10436 --- [pool-2-thread-1] my.test.TestEntityLogger                 : TestEntity{id=1, name='test_one'}
2016-06-20 10:46:23.090  INFO 10436 --- [pool-2-thread-1] my.test.TestEntityLogger                 : TestEntity{id=2, name='test_two'}
2016-06-20 10:46:23.090  INFO 10436 --- [pool-2-thread-1] my.test.TestEntityLogger                 : TestEntity{id=3, name='test_three'}
2016-06-20 10:46:23.091  INFO 10436 --- [pool-2-thread-1] my.test.TestEntityLogger                 : TestEntity{id=4, name='test_four'}
2016-06-20 10:46:23.091  INFO 10436 --- [pool-2-thread-1] my.test.TestEntityLogger                 : TestEntity{id=5, name='test_five'}
2016-06-20 10:46:23.091  INFO 10436 --- [pool-2-thread-1] my.test.TestEntityLogger                 : TestEntity{id=6, name='test_six'}
2016-06-20 10:46:23.091  INFO 10436 --- [pool-2-thread-1] my.test.TestEntityLogger                 : TestEntity{id=7, name='test_seven'}
2016-06-20 10:46:23.092  INFO 10436 --- [pool-2-thread-1] my.test.TestEntityLogger                 : Finished reading the stream. It should be closed by now.
2016-06-20 10:47:01.998  WARN 10436 --- [:1466408776991]] o.a.tomcat.jdbc.pool.ConnectionPool      : Connection has been abandoned PooledConnection[conn9: url=jdbc:h2:mem:testdb user=SA]:java.lang.Exception
    at org.apache.tomcat.jdbc.pool.ConnectionPool.getThreadDump(ConnectionPool.java:1061)
    at org.apache.tomcat.jdbc.pool.ConnectionPool.borrowConnection(ConnectionPool.java:777)
    at org.apache.tomcat.jdbc.pool.ConnectionPool.borrowConnection(ConnectionPool.java:626)
    at org.apache.tomcat.jdbc.pool.ConnectionPool.getConnection(ConnectionPool.java:185)
    at org.apache.tomcat.jdbc.pool.DataSourceProxy.getConnection(DataSourceProxy.java:127)
    at org.hibernate.engine.jdbc.connections.internal.DatasourceConnectionProviderImpl.getConnection(DatasourceConnectionProviderImpl.java:139)
    at org.hibernate.internal.AbstractSessionImpl$NonContextualJdbcConnectionAccess.obtainConnection(AbstractSessionImpl.java:380)
    at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.obtainConnection(LogicalConnectionImpl.java:228)
    at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.getConnection(LogicalConnectionImpl.java:171)
    at org.hibernate.engine.jdbc.internal.StatementPreparerImpl.connection(StatementPreparerImpl.java:63)
    at org.hibernate.engine.jdbc.internal.StatementPreparerImpl$5.doPrepare(StatementPreparerImpl.java:162)
    at org.hibernate.engine.jdbc.internal.StatementPreparerImpl$StatementPreparationTemplate.prepareStatement(StatementPreparerImpl.java:186)
    at org.hibernate.engine.jdbc.internal.StatementPreparerImpl.prepareQueryStatement(StatementPreparerImpl.java:160)
    at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1885)
    at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1862)
    at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1839)
    at org.hibernate.loader.Loader.scroll(Loader.java:2627)
    at org.hibernate.loader.hql.QueryLoader.scroll(QueryLoader.java:561)
    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.scroll(QueryTranslatorImpl.java:439)
    at org.hibernate.engine.query.spi.HQLQueryPlan.performScroll(HQLQueryPlan.java:355)
    at org.hibernate.internal.SessionImpl.scroll(SessionImpl.java:1381)
    at org.hibernate.internal.QueryImpl.scroll(QueryImpl.java:91)
    at org.springframework.data.jpa.provider.PersistenceProvider$HibernateScrollableResultsIterator.<init>(PersistenceProvider.java:414)
    at org.springframework.data.jpa.provider.PersistenceProvider$1.executeQueryWithResultStream(PersistenceProvider.java:118)
    at org.springframework.data.jpa.repository.query.JpaQueryExecution$StreamExecution.doExecute(JpaQueryExecution.java:323)
    at org.springframework.data.jpa.repository.query.JpaQueryExecution.execute(JpaQueryExecution.java:78)
    at org.springframework.data.jpa.repository.query.AbstractJpaQuery.doExecute(AbstractJpaQuery.java:100)
    at org.springframework.data.jpa.repository.query.AbstractJpaQuery.execute(AbstractJpaQuery.java:91)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.doInvoke(RepositoryFactorySupport.java:462)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:440)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:61)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)
    at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:281)
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:136)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:131)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:208)
    at my.test.$Proxy55.findEntities(Unknown Source)
    at my.test.TestEntityLogger.logAllTestEntities(StreamErrorAppRunner.java:59)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.springframework.scheduling.support.ScheduledMethodRunnable.run(ScheduledMethodRunnable.java:65)
    at org.springframework.scheduling.support.DelegatingErrorHandlingRunnable.run(DelegatingErrorHandlingRunnable.java:54)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)

[thomasdarimont]

@TarmoKalling since there is no JIRA issue yet I’m replying here.

if you add @Transactional(readOnly = true) to the logAllTestEntities() method then the connection should be released properly - according to a quick test.

cc @olivergierke FYI

Cheers, Thomas

[gokhanoner]

@TarmoKalling if you can use Hibernate 5.2, here is a workaround for you 😉 (tested with spring-boot 1.4.1 and hibernate 5.2.3.Final )

@Component
class MyRepo {

    private final EntityManager entityManager;

    @Autowired
    private MyRepo(EntityManager entityManager) {
        this.entityManager = entityManager;
    }


    public Stream<TestEntity> findEntities() {
        return entityManager.unwrap(Session.class).createQuery("select t from TestEntity t", ToKas.class).setReadOnly(true).setFetchSize(1000).stream();
    }

}

@Transactional(readOnly = true) annotation needs to be on the method that process the Stream, on in your case on the logAllTestEntities Method, otherwise it closes the stream after method call.

I run this on H2 & Oracle DB with 500K records, works perfect.