如何解决 tomcat 内存泄漏警告 - Web 应用程序已启动线程但未能停止它答案

【问题标题】：How to resolve tomcat memory leak warning - The web application have started a thread but has failed to stop it如何解决 tomcat 内存泄漏警告 - Web 应用程序已启动线程但未能停止它
【发布时间】：2017-12-07 22:44:30
【问题描述】：

我正在使用 com.ning.async-http-client(1.9.40) 库来发布异步请求。在关闭 tomcat 时，我在 catalina.out 日志中收到以下消息：-

SEVERE: The web application [/xyz] appears to have started a thread named [Hashed wheel timer #1] but has failed to stop it. This is very likely to create a memory leak.
Jul 03, 2017 1:27:15 PM org.apache.catalina.loader.WebappClassLoaderBase clearReferencesThreads
SEVERE: The web application [/xyz] appears to have started a thread named [New I/O worker #1] but has failed to stop it. This is very likely to create a memory leak.
Jul 03, 2017 1:27:15 PM org.apache.catalina.loader.WebappClassLoaderBase clearReferencesThreads
SEVERE: The web application [/xyz] appears to have started a thread named [New I/O worker #2] but has failed to stop it. This is very likely to create a memory leak.
Jul 03, 2017 1:27:15 PM org.apache.catalina.loader.WebappClassLoaderBase clearReferencesThreads
SEVERE: The web application [/xyz] appears to have started a thread named [New I/O boss #3] but has failed to stop it. This is very likely to create a memory leak.
Jul 03, 2017 1:27:15 PM org.apache.catalina.loader.WebappClassLoaderBase clearReferencesThreads
SEVERE: The web application [/xyz] appears to have started a thread named [Hashed wheel timer #2] but has failed to stop it. This is very likely to create a memory leak.**

这些线程的状态是：

"New I/O boss #3" prio=10 tid=0x00007ff3a00f9000 nid=0x17a9 runnable [0x00007ff3878f7000]
"New I/O worker #2" daemon prio=10 tid=0x00007ff3a00aa800 nid=0x17a8 runnable [0x00007ff3879f8000]
"New I/O worker #1" daemon prio=10 tid=0x00007ff3a00b8800 nid=0x17a7 runnable [0x00007ff387af9000]
"Hashed wheel timer #2" prio=10 tid=0x00007ff3a020e800 nid=0x17aa waiting on condition [0x00007ff3875f0000]
"Hashed wheel timer #1" prio=10 tid=0x00007ff3a0083000 nid=0x17a6 sleeping[0x00007ff387bfa000]

请提出一种方法来阻止应用程序中的这些线程。

【问题讨论】：

标签： java tomcat memory-leaks asynchttpclient

【解决方案1】：

AsyncHttpClient 实现了Closeable。当您的应用程序关闭时，调用close() 就足够了。

这将清理AsyncHttpClient使用的资源。

为了说明：

public static void main(String[] args) throws Exception {
    AsyncHttpClient asyncHttpClient = new AsyncHttpClient();
    Future<Response> f = asyncHttpClient.prepareGet("http://www.google.com/").execute();
    Response r = f.get();

    asyncHttpClient.close(); // when this is commented out, the application won't exit, as the non daemon threads prevent it.
}

【讨论】：