java - 未能停止 Tomcat 中的 Elasticsearch 线程

Question

我正在为基于 Spring MVC 的网站使用 Tomcat 8.x。网站调用Elasticsearch的方式如下:

private static Client client;

以下是我如何只创建一次客户端对象:

public static Client getClient() {
    if (client == null) {           
        Settings settings = Settings.settingsBuilder()
                .put("cluster.name", "my_cluster")
                .build();
                
        try {
            TransportAddress[] transportAddress = new TransportAddress[1];
            for (int k=0; k<adds.length; k++) {
                transportAddress[0] = new InetSocketTransportAddress(InetAddress.getByName('127.0.0.1'), 9300);
            }
            client = TransportClient.builder().settings(settings)
                    .addPlugin(DeleteByQueryPlugin.class)
                    .build()
                    .addTransportAddresses(transportAddress);
        
        } catch (UnknownHostException e) {
            logger.error("Failed to get ES client");;
        }           
    }       
    
    return client;
}

下面是我使用客户端访问Elasticsearch的方式:

public SearchResponse searchForMyPage(Long owerId, HttpServletRequest request, Account visitor, CampaignResultType type) {

    String query = 'this is my query string';
    
    if (client == null) {
        client = getClient();
    }
    
    SearchResponse sr = client.prepareSearch('MyIndex')
            .setTypes('MyDoc'))
            .setQuery(query)
            .setHighlighterNumOfFragments(1)
            .setSize(10).execute().actionGet();         
    return sr;
}

但我在 Tomcat 日志中看到许多与 Elasticsearch 相关的异常。类似于以下内容:

19-May-2016 00:52:13.483 WARNING [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [ROOT] appears to have started a thread named [elasticsearch[Volpan][transport_client_worker][T#9]{New I/O worker #9}] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:

在 Java 网络应用程序中使用 Elasticsearch 的正确方法是什么？

更新

以下是 Tomcat 的日志，显示了从 Tomcat 启动到关闭的许多 Elasticsearch 相关错误。

20-May-2016 21:43:11.219 WARNING [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [ROOT] appears to have started a thread named [elasticsearch[War Machine][[timer]]] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
 java.lang.Thread.sleep(Native Method)
 org.elasticsearch.threadpool.ThreadPool$EstimatedTimeThread.run(ThreadPool.java:703)
20-May-2016 21:43:11.219 WARNING [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [ROOT] appears to have started a thread named [elasticsearch[War Machine][scheduler][T#1]] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
 sun.misc.Unsafe.park(Native Method)
 java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215)
 java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2078)
 java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1093)
 java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:809)
 java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067)
 java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127)
 java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
 java.lang.Thread.run(Thread.java:745)
20-May-2016 21:43:11.220 WARNING [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [ROOT] appears to have started a thread named [elasticsearch[War Machine][transport_client_worker][T#1]{New I/O worker #1}] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
 sun.nio.ch.WindowsSelectorImpl$SubSelector.poll0(Native Method)
 sun.nio.ch.WindowsSelectorImpl$SubSelector.poll(WindowsSelectorImpl.java:296)
 sun.nio.ch.WindowsSelectorImpl$SubSelector.access$400(WindowsSelectorImpl.java:278)
 sun.nio.ch.WindowsSelectorImpl.doSelect(WindowsSelectorImpl.java:159)
 sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86)
 sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97)
 org.jboss.netty.channel.socket.nio.SelectorUtil.select(SelectorUtil.java:68)
 org.jboss.netty.channel.socket.nio.AbstractNioSelector.select(AbstractNioSelector.java:434)
 org.jboss.netty.channel.socket.nio.AbstractNioSelector.run(AbstractNioSelector.java:212)
 org.jboss.netty.channel.socket.nio.AbstractNioWorker.run(AbstractNioWorker.java:89)
 org.jboss.netty.channel.socket.nio.NioWorker.run(NioWorker.java:178)
 org.jboss.netty.util.ThreadRenamingRunnable.run(ThreadRenamingRunnable.java:108)
 org.jboss.netty.util.internal.DeadLockProofWorker$1.run(DeadLockProofWorker.java:42)
 java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
 java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
 java.lang.Thread.run(Thread.java:745)
20-May-2016 21:43:11.221 WARNING [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [ROOT] appears to have started a thread named [elasticsearch[War Machine][transport_client_worker][T#2]{New I/O worker #2}] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
 sun.nio.ch.WindowsSelectorImpl$SubSelector.poll0(Native Method)
 sun.nio.ch.WindowsSelectorImpl$SubSelector.poll(WindowsSelectorImpl.java:296)
 sun.nio.ch.WindowsSelectorImpl$SubSelector.access$400(WindowsSelectorImpl.java:278)
 sun.nio.ch.WindowsSelectorImpl.doSelect(WindowsSelectorImpl.java:159)
 sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86)
 sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97)
 org.jboss.netty.channel.socket.nio.SelectorUtil.select(SelectorUtil.java:68)
 org.jboss.netty.channel.socket.nio.AbstractNioSelector.select(AbstractNioSelector.java:434)
 org.jboss.netty.channel.socket.nio.AbstractNioSelector.run(AbstractNioSelector.java:212)
 org.jboss.netty.channel.socket.nio.AbstractNioWorker.run(AbstractNioWorker.java:89)
 org.jboss.netty.channel.socket.nio.NioWorker.run(NioWorker.java:178)
 org.jboss.netty.util.ThreadRenamingRunnable.run(ThreadRenamingRunnable.java:108)
 org.jboss.netty.util.internal.DeadLockProofWorker$1.run(DeadLockProofWorker.java:42)
 java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
 java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
 java.lang.Thread.run(Thread.java:745)
20-May-2016 21:43:11.221 WARNING [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [ROOT] appears to have started a thread named [elasticsearch[War Machine][transport_client_worker][T#3]{New I/O worker #3}] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
 sun.nio.ch.WindowsSelectorImpl$SubSelector.poll0(Native Method)
 sun.nio.ch.WindowsSelectorImpl$SubSelector.poll(WindowsSelectorImpl.java:296)
 sun.nio.ch.WindowsSelectorImpl$SubSelector.access$400(WindowsSelectorImpl.java:278)
 sun.nio.ch.WindowsSelectorImpl.doSelect(WindowsSelectorImpl.java:159)
 sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86)
 sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97)
 org.jboss.netty.channel.socket.nio.SelectorUtil.select(SelectorUtil.java:68)
 org.jboss.netty.channel.socket.nio.AbstractNioSelector.select(AbstractNioSelector.java:434)
 org.jboss.netty.channel.socket.nio.AbstractNioSelector.run(AbstractNioSelector.java:212)
 org.jboss.netty.channel.socket.nio.AbstractNioWorker.run(AbstractNioWorker.java:89)
 org.jboss.netty.channel.socket.nio.NioWorker.run(NioWorker.java:178)
 org.jboss.netty.util.ThreadRenamingRunnable.run(ThreadRenamingRunnable.java:108)
 org.jboss.netty.util.internal.DeadLockProofWorker$1.run(DeadLockProofWorker.java:42)
 java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
 java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
 java.lang.Thread.run(Thread.java:745)
20-May-2016 21:43:11.222 WARNING [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [ROOT] appears to have started a thread named [elasticsearch[War Machine][transport_client_worker][T#4]{New I/O worker #4}] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
 sun.nio.ch.WindowsSelectorImpl$SubSelector.poll0(Native Method)
 sun.nio.ch.WindowsSelectorImpl$SubSelector.poll(WindowsSelectorImpl.java:296)
 sun.nio.ch.WindowsSelectorImpl$SubSelector.access$400(WindowsSelectorImpl.java:278)
 sun.nio.ch.WindowsSelectorImpl.doSelect(WindowsSelectorImpl.java:159)
 sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86)
 sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97)
 org.jboss.netty.channel.socket.nio.SelectorUtil.select(SelectorUtil.java:68)
 org.jboss.netty.channel.socket.nio.AbstractNioSelector.select(AbstractNioSelector.java:434)
 org.jboss.netty.channel.socket.nio.AbstractNioSelector.run(AbstractNioSelector.java:212)
 org.jboss.netty.channel.socket.nio.AbstractNioWorker.run(AbstractNioWorker.java:89)
 org.jboss.netty.channel.socket.nio.NioWorker.run(NioWorker.java:178)
 org.jboss.netty.util.ThreadRenamingRunnable.run(ThreadRenamingRunnable.java:108)
 org.jboss.netty.util.internal.DeadLockProofWorker$1.run(DeadLockProofWorker.java:42)
 java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
 java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
 java.lang.Thread.run(Thread.java:745)
20-May-2016 21:43:11.223 WARNING [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [ROOT] appears to have started a thread named [elasticsearch[War Machine][transport_client_worker][T#5]{New I/O worker #5}] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
 sun.nio.ch.WindowsSelectorImpl$SubSelector.poll0(Native Method)
 

Answer 1

您需要在应用程序关闭时调用 client.close()。你如何做到这一点取决于你的 Java 网络应用程序的细节。

例如(代码复制自 this stackoverflow answer )，适用于 Servlet 3.0 spec :

@WebListener
public class BackgroundJobManager implements ServletContextListener {

    private ScheduledExecutorService scheduler;

    @Override
    public void contextInitialized(ServletContextEvent event) {
        scheduler = Executors.newSingleThreadScheduledExecutor();
        scheduler.scheduleAtFixedRate(new YourParsingJob(), 0, 5, TimeUnit.HOUR);
    }

    @Override
    public void contextDestroyed(ServletContextEvent event) {
        scheduler.shutdownNow();
    }

}

或者使用 Spring，在您创建客户端的类中，定义一个 @PreDestroy 注释方法并在那里调用 client.close():

@PreDestroy
public void destroy() {
  client.close();
}