mysql - 停止/重新部署时 Tomcat 7+ 内存泄漏。 Spring Data、JPA、Hibernate、MySQL

Question

我在停止/重新部署应用程序时遇到 tomcat 内存泄漏问题。它说 以下 Web 应用程序已停止(重新加载、取消部署)，但它们的之前运行的类仍然加载在内存中，从而导致内存泄漏(使用分析器确认):/test-1.0-SNAPSHOT

MySQL 连接器驱动程序位于 Tomcat/lib 文件夹中。我可以在两者中重现此问题:Tomcat 7/8。还尝试使用“net.sourceforge.jtds.*”驱动程序的 MS SQL 数据库，但没有帮助。

请在下面找到项目文件。项目仅在数据库中创建 1 个表。

build.gradle

group 'com.test'
version '1.0-SNAPSHOT'

apply plugin: 'java'
apply plugin: 'war'
sourceCompatibility = 1.8
repositories {
    mavenCentral()
}
dependencies {
    compile group: 'org.hibernate', name: 'hibernate-entitymanager', version: '5.2.10.Final'
    compile group: 'org.springframework.data', name: 'spring-data-jpa', version: '1.11.4.RELEASE'
    compile group: 'org.springframework', name: 'spring-webmvc', version: '4.3.9.RELEASE'
    providedCompile 'javax.servlet:javax.servlet-api:3.1.0'
    providedCompile group: 'mysql', name: 'mysql-connector-java', version: '5.1.6'
    compile group: 'commons-dbcp', name: 'commons-dbcp', version: '1.4'
}

ApplicationConfig.java

@Configuration
@Import({JPAConfiguration.class})
@EnableWebMvc
public class ApplicationConfig {}

JPAConfiguration.java

@Configuration
@EnableJpaRepositories("com.test.dao")
@EnableTransactionManagement
public class JPAConfiguration {

    @Bean
    public EntityManagerFactory entityManagerFactory() {
        LocalContainerEntityManagerFactoryBean factory = new LocalContainerEntityManagerFactoryBean();
        factory.setJpaVendorAdapter(new HibernateJpaVendorAdapter());
        factory.setPackagesToScan("com.test.model");
        factory.setDataSource(restDataSource());
        factory.setJpaPropertyMap(getPropertyMap());
        factory.afterPropertiesSet();
        return factory.getObject();
    }

    @Bean(destroyMethod = "close")
    public DataSource restDataSource() {
        BasicDataSource dataSource = new BasicDataSource();
        dataSource.setDriverClassName("com.mysql.jdbc.Driver");
        dataSource.setUrl("jdbc:mysql://localhost:3306/test");
        dataSource.setUsername("test");
        dataSource.setPassword("test");
        return dataSource;
    }

    private Map<String, String> getPropertyMap() {
        Map<String, String> hibernateProperties = new HashMap<>();
        hibernateProperties.put("hibernate.hbm2ddl.auto", "update");
        hibernateProperties.put("hibernate.show_sql", "true");
        hibernateProperties.put("hibernate.format_sql", "true");
        hibernateProperties.put("hibernate.dialect", "org.hibernate.dialect.MySQL5InnoDBDialect");
        return hibernateProperties;
    }

    @Bean
    public PlatformTransactionManager transactionManager() {
        JpaTransactionManager txManager = new JpaTransactionManager();
        txManager.setEntityManagerFactory(entityManagerFactory());
        return txManager;
    }

}

TestRepository.java

@Repository
public interface TestRepository extends JpaRepository<TestEntity, Long> {}

TestEntity.java

@Entity
@Table(name = "ent")
public class TestEntity {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String descript;
    //equals, hashcode, toString, getters, setters
}

AppInitializer.java

public class AppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {
    private WebApplicationContext rootContext;

    @Override
    protected Class<?>[] getRootConfigClasses() {
        return new Class[]{ApplicationConfig.class};
    }

    @Override
    protected Class<?>[] getServletConfigClasses() {
        return null;
    }

    @Override
    protected String[] getServletMappings() {
        return new String[]{"/"};
    }

}

命令

jmap -histo <tomcat_pid>

在 tomcat 停止后仅显示项目结构中的 2 项:

com.test.config.dao.JPAConfiguration$$EnhancerBySpringCGLIB$$792cb231$$FastClassBySpringCGLIB$$45ff499c
com.test.config.dao.JPAConfiguration$$FastClassBySpringCGLIB$$10104c1e

有人有解决此问题的想法或建议吗？

Answer 1

这个小项目有2处内存泄漏:

1. MySQL jdbc 驱动程序的问题。

我们必须添加 ContextLoaderListener 来注销 jdbc 驱动程序:

听众:

@WebListener
public class ContextListener extends ContextLoaderListener {

    private final Logger log = LoggerFactory.getLogger(this.getClass());

    @Override
    public void contextInitialized(ServletContextEvent sce) {
        log.info("-= Context started =-");

    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        super.contextDestroyed(sce);
        log.info("-= Context destroyed =-");
        try {
            log.info("Calling MySQL AbandonedConnectionCleanupThread checkedShutdown");
            com.mysql.cj.jdbc.AbandonedConnectionCleanupThread.uncheckedShutdown();

        } catch (Exception e) {
            log.error("Error calling MySQL AbandonedConnectionCleanupThread checkedShutdown {}", e);
        }

        ClassLoader cl = Thread.currentThread().getContextClassLoader();

        Enumeration<Driver> drivers = DriverManager.getDrivers();
        while (drivers.hasMoreElements()) {
            Driver driver = drivers.nextElement();

            if (driver.getClass().getClassLoader() == cl) {

                try {
                    log.info("Deregistering JDBC driver {}", driver);
                    DriverManager.deregisterDriver(driver);

                } catch (SQLException ex) {
                    log.error("Error deregistering JDBC driver {}", driver, ex);
                }

            } else {
                log.info("Not deregistering JDBC driver {} as it does not belong to this webapp's ClassLoader", driver);
            }
        }
    }
}

或者如果您可以访问 tomcat 服务器，您可以在 tomcat/conf/server.xml 中修改监听器 example .

1. 第二个问题是 jboss-logging 库中的已知内存泄漏 (link)。

在我们将这个库从 hibernate 依赖项中排除后，内存泄漏就消失了:

build.gradle:

group 'com.test'
version '1.0-SNAPSHOT'

apply plugin: 'java'
apply plugin: 'war'
sourceCompatibility = 1.8
repositories {
    mavenCentral()
}
dependencies {
    compile(group: 'org.hibernate', name: 'hibernate-entitymanager', version: '5.2.10.Final') {
        exclude group: 'org.jboss.logging', module: 'jboss-logging'
    }

    compile group: 'org.springframework.data', name: 'spring-data-jpa', version: '1.11.4.RELEASE'

    compile group: 'org.springframework', name: 'spring-webmvc', version: '4.3.9.RELEASE'

    providedCompile 'javax.servlet:javax.servlet-api:3.1.0'
    providedCompile group: 'mysql', name: 'mysql-connector-java', version: '8.0.11'
    compile group: 'org.slf4j', name: 'slf4j-api', version: '1.7.25'
    compile group: 'org.slf4j', name: 'slf4j-simple', version: '1.7.25'
}

然后从 repo 构建 jar并添加到 tomcat /lib 文件夹。

jboss-logging 的问题可能已在 Java 9 ( pull request link ) 中修复。