Spring + Quartz = Memory Leaks

Question

I use the following libraries.

• quartz-2.2.1
• spring-webmvc-3.2.9.RELEASE

on Apache Tomcat/7.0.52 (Ubuntu).

I use Spring to configure Quartz.

@Configuration
class QuartzConfig {
    @Bean
    FactoryBean<Scheduler> scheduler() {
        final SchedulerFactoryBean factory = new SchedulerFactoryBeanWithShutdownDelay();
        final Map<String, Object> map = new LinkedHashMap<>();
        map.put("settingsService", settingsService);
        final List<AbstractQuartzJob> jobs = new LinkedList<>();
        jobs.add(dbBackupJob());
        jobs.add(csvExportJob());
        jobs.add(csvImportJob());
        jobs.add(dbMaintenanceJob());
        jobs.add(filesystemCleanupJob());
        map.put("jobs", jobs);
        factory.setSchedulerContextAsMap(map);
        factory.setTriggers(new Trigger[] {cronTrigger});
        return factory;
    }
}

Searched a lot today why the scheduler tasks where not shut down correctly...

Jun 24, 2014 5:14:38 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/feeder##1.5.0] appears to have started a thread named [scheduler_Worker-1] but has failed to stop it. This is very likely to create a memory leak.
Jun 24, 2014 5:14:38 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/feeder##1.5.0] appears to have started a thread named [scheduler_Worker-2] but has failed to stop it. This is very likely to create a memory leak.
Jun 24, 2014 5:14:38 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/feeder##1.5.0] appears to have started a thread named [scheduler_Worker-3] but has failed to stop it. This is very likely to create a memory leak.
Jun 24, 2014 5:14:38 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/feeder##1.5.0] appears to have started a thread named [scheduler_Worker-4] but has failed to stop it. This is very likely to create a memory leak.
Jun 24, 2014 5:14:38 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/feeder##1.5.0] appears to have started a thread named [scheduler_Worker-5] but has failed to stop it. This is very likely to create a memory leak.
Jun 24, 2014 5:14:38 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/feeder##1.5.0] appears to have started a thread named [scheduler_Worker-6] but has failed to stop it. This is very likely to create a memory leak.
Jun 24, 2014 5:14:38 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/feeder##1.5.0] appears to have started a thread named [scheduler_Worker-7] but has failed to stop it. This is very likely to create a memory leak.
Jun 24, 2014 5:14:38 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/feeder##1.5.0] appears to have started a thread named [scheduler_Worker-8] but has failed to stop it. This is very likely to create a memory leak.
Jun 24, 2014 5:14:38 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/feeder##1.5.0] appears to have started a thread named [scheduler_Worker-9] but has failed to stop it. This is very likely to create a memory leak.
Jun 24, 2014 5:14:38 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/feeder##1.5.0] appears to have started a thread named [scheduler_Worker-10] but has failed to stop it. This is very likely to create a memory leak.

The ugly hack was to write the SchedulerFactoryBeanWithShutdownDelay class.

public class SchedulerFactoryBeanWithShutdownDelay extends SchedulerFactoryBean {
    private static final int SHUTDOWN_TIMEOUT = 2000;

    @Override
    public void destroy() throws SchedulerException {
        log.debug("Start shutdown of Quartz scheduler factory bean");
        super.destroy();
        try {
            log.debug("wait {}ms to shutdown Quartz", SHUTDOWN_TIMEOUT);
            Thread.sleep(SHUTDOWN_TIMEOUT);
            log.debug("Quartz scheduler shutdown completed");
        } catch (InterruptedException e) {
            log.error("", e);
        }
    }
}

But this issue should have been closed: https://jira.terracotta.org/jira/browse/QTZ-192

Have I made a mistake or can this be confirmed?

Answer 1

An excellent article on memory leaks in Tomcat. Read the article, start your web app, let Quartz jobs execute, then stop the web app, then take a heap dump of Tomcat's JVM, load the heap dump into Eclipse MAT and find out which classes cause memory leaks. Then you should be able to fix the issue.