Tomcat中的Quartz调度程序内存泄漏

Question

我使用石英版2.2.2和Spring Boot版1.3.1。它表现正常，一切正常。但是当我试图关闭这个应用程序时，问题出现了。日志显示有内存泄漏...

我的石英配置；

org.quartz.scheduler.instanceName = my-app-jobs
org.quartz.scheduler.instanceId = AUTO
org.quartz.threadPool.threadCount=2
org.quartz.jobStore.class = org.quartz.simpl.RAMJobStore
org.quartz.threadPool.class = org.quartz.simpl.SimpleThreadPool
org.quartz.scheduler.skipUpdateCheck = true

我有两个班，执行如下工作；

/**
 *
 * To Run Every 15 Minutes
 *
 */
public class MemoryDataUpdateJob implements Job {

    @Autowired
    private Dao dao;

    @Override
    public void execute(JobExecutionContext context) throws JobExecutionException {
        Logger.info(getClass().getName(), "Scheduled Memory Data Update Job Started...");

        //Read Device Settings
        dao.readDeviceSettings();

        Logger.info(getClass().getName(), "Scheduled Memory Data Update Job Finished.");
    }

}

另一个班也同样做着不同的事情。

调度器工厂Bean如下；

@Bean
public SchedulerFactoryBean schedulerFactoryBean(
        JobFactory jobFactory,
        @Qualifier("MemoryDataUpdateJobTrigger") Trigger memoryDataUpdateJobTrigger,
        @Qualifier("MsgCountJobTrigger") Trigger msgCountJobTrigger) throws IOException {
    SchedulerFactoryBean factory = new SchedulerFactoryBean();
    factory.setJobFactory(jobFactory);
    factory.setQuartzProperties(quartzProperties());
    factory.setTriggers(memoryDataUpdateJobTrigger, msgCountJobTrigger);
    return factory;
}

我得到了像下面这样的tomcat日志；

19-Jan-2016 11:18:39.722 WARNING [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [MyApp-1.0.0] appears to have started a thread named [schedulerFactoryBean_Worker-1] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
 java.lang.Object.wait(Native Method)

19-Jan-2016 11:18:39.722 WARNING [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [MyApp-1.0.0] appears to have started a thread named [schedulerFactoryBean_Worker-2] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
 java.lang.Object.wait(Native Method)

查阅了quartz文档，并在properties中添加了以下内容：；

org.quartz.plugin.shutdownhook.class = org.quartz.plugins.management.ShutdownHookPlugin
org.quartz.plugin.shutdownhook.cleanShutdown = true

第一条线程消息消失了，但关于worker-2的第二条消息仍然存在。

但在我的应用程序记录器中，我看到了这样的内容；

[2016-01-19 11:18:39:681] [DEBUG] [schedulerFactoryBean_Worker-1] [org.quartz.simpl.SimpleThreadPool:612] - WorkerThread is shut down.

[2016-01-19 11:18:40:047] [DEBUG] [schedulerFactoryBean_Worker-2] [org.quartz.simpl.SimpleThreadPool:612] - WorkerThread is shut down.

[2016-01-19 11:18:40:049] [INFO ] [Quartz Shutdown-Hook schedulerFactoryBean] [org.quartz.plugins.management.ShutdownHookPlugin:126] - Shutting down Quartz...

问题是什么？为什么即使应用程序记录器显示线程已关闭，也会出现内存泄漏？

Answer 1

至少从Spring 3.0开始，SchedulerFactoryBean就有一个标志来告诉它等待作业完成。设置标志并确保在关闭时调用销毁方法：

@Bean(destroyMethodName="destroy")
public SchedulerFactoryBean schedulerFactoryBean(
        JobFactory jobFactory,
        @Qualifier("MemoryDataUpdateJobTrigger") Trigger memoryDataUpdateJobTrigger,
        @Qualifier("MsgCountJobTrigger") Trigger msgCountJobTrigger) throws IOException {
    SchedulerFactoryBean factory = new SchedulerFactoryBean();
    factory.setWaitForJobsToCompleteOnShutdown(true);
    factory.setJobFactory(jobFactory);
    factory.setQuartzProperties(quartzProperties());
    factory.setTriggers(memoryDataUpdateJobTrigger, msgCountJobTrigger);
    return factory;
}

或使用XML配置：

<bean id="scheduler"
        class="org.springframework.scheduling.quartz.SchedulerFactoryBean"
        destroy-method="destroy">
    <property name="waitForJobsToCompleteOnShutdown" value="true" />
    ....
</bean>

请参阅：https://docs.spring.io/spring-framework/docs/3.0.0.RELEASE/javadoc-api/org/springframework/scheduling/quartz/SchedulerFactoryBean.html#setWaitForJobsToCompleteOnShutdown（布尔）

Answer 2

知道了。问题是tomcat正在关闭，但quartz作业正在运行。如果我们等待一秒钟，它就会正常关闭。我们可以通过扩展SchedulerFactoryBean并重写它的destroy方法来实现。如下所示；

public class SchedulerFactoryBeanWithWait extends SchedulerFactoryBean {

@Override
public void destroy() throws SchedulerException {
    super.destroy();
    try {
        Thread.sleep(1000);
    } catch (InterruptedException e) {
        logError(e);
    }
 }
}

和bean声明；

@Bean
public SchedulerFactoryBeanWithWait schedulerFactoryBeanWithWait (
        JobFactory jobFactory,
        @Qualifier("MemoryDataUpdateJobTrigger") Trigger memoryDataUpdateJobTrigger,
        @Qualifier("MsgCountJobTrigger") Trigger msgCountJobTrigger) throws IOException {
    SchedulerFactoryBeanWithWait factory = new SchedulerFactoryBeanWithWait ();
    factory.setJobFactory(jobFactory);
    factory.setQuartzProperties(quartzProperties());
    factory.setTriggers(memoryDataUpdateJobTrigger, msgCountJobTrigger);
    return factory;
}

这使得它等待线程关闭。也许这对将来的人有帮助。