java - Netty 导致 tomcat 内存泄漏

Question

我正在使用 Netty 4.0.26.Final 和 Tomcat 8 在 Web 应用程序中实现嵌入式 TCP 服务器。

问题是，当我停止 Tomcat 时，我收到了这条消息:

The web application [app] appears to have started a thread named 

[nioEventLoopGroup-2-1] 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:87)
 sun.nio.ch.SelectorImpl.select(SelectorImpl.java:98)
 io.netty.channel.nio.NioEventLoop.select(NioEventLoop.java:622)
 io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:310)
 io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:111)
 io.netty.util.concurrent.DefaultThreadFactory$DefaultRunnableDecorator.run(DefaultThreadFactory.java:137)

我已经尝试使用此类在关闭 tomcat 之前关闭线程，但我仍然遇到同样的问题。

@Component
public class MyAppServletContextListener implements ServletContextListener{

    @Override
    public void contextInitialized(ServletContextEvent arg0) {
    }


    @Override
    public void contextDestroyed(ServletContextEvent arg0) {
        TrackingDaemon trackingDaemon= (TrackingDaemon) ApplicationContextProvider.getBean("trackingDaemon");
        trackingDaemon.bossGroup.shutdownGracefully();
        trackingDaemon.workerGroup.shutdownGracefully();
    }


}

BossGroup 和 workerGroup 是:

EventLoopGroup bossGroup = new NioEventLoopGroup(); 
EventLoopGroup workerGroup = new NioEventLoopGroup();

任何帮助将不胜感激..

Answer 1

我在 netty 4 和 tomcat 7 上遇到过这个问题，并通过从 shutdownGracefully() 捕获 future 事件并等待其完成来解决它。关闭应用程序时调用以下方法。

private void stopChannel() {
 log.trace("Stopping server socket on port '{}'", port);
 sendMessageService.deregisterMessageSender(endpointId);
 try {
   for (Channel channel : channels) {
     if (channel != null) {
       channel.close();
     }
   }
   serverChannel.close().sync();
   log.trace("Server socket on port '{}' stopped.", port);
 } catch (InterruptedException e) {
    throw new RuntimeException(e);
 } finally {
    Future<?> fc = connectionGroup.shutdownGracefully();
    Future<?> fw = workerGroup.shutdownGracefully();
   try {
     fc.await(); // when shutting down in tomcat waits for the netty threads to die
     fw.await();
   } catch (InterruptedException e) {
    throw new RuntimeException(e);
  }
   log.trace("Server workerGroup has shutdown successfully on port '{}'", port);
}