用Redis实现Spring会话时的`io.netty`异常

Question

我正在使用Redis实现Spring会话。

我得到了以下例外：

SEVERE [RMI TCP Connection(3)-127.0.0.1]
org.apache.catalina.loader.WebappClassLoaderBase.checkThreadLocalMapForLeaks 
The web application [ROOT] created a ThreadLocal with key of type [java.lang.ThreadLocal] 
(value [java.lang.ThreadLocal@e9d8bb]) and a value of type [io.netty.util.internal.InternalThreadLocalMap] 
(value [io.netty.util.internal.InternalThreadLocalMap@1559b23]) 
but failed to remove it when the web application was stopped. Threads are going to be 
renewed over time to try and avoid a probable memory leak.

我有以下依赖关系：

    <dependency>
        <groupId>io.lettuce</groupId>
        <artifactId>lettuce-core</artifactId>
        <version>5.2.1.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.session</groupId>
        <artifactId>spring-session-data-redis</artifactId>
        <version>2.2.1.RELEASE</version>
    </dependency>

我可以看到lettuce-core正在拖动io.netty类：

[INFO] +- io.lettuce:lettuce-core:jar:5.2.1.RELEASE:compile
[INFO] |  +- io.netty:netty-common:jar:4.1.43.Final:compile
[INFO] |  +- io.netty:netty-handler:jar:4.1.43.Final:compile
[INFO] |  |  +- io.netty:netty-buffer:jar:4.1.43.Final:compile
[INFO] |  |  \- io.netty:netty-codec:jar:4.1.43.Final:compile
[INFO] |  +- io.netty:netty-transport:jar:4.1.43.Final:compile
[INFO] |  |  \- io.netty:netty-resolver:jar:4.1.43.Final:compile
[INFO] |  \- io.projectreactor:reactor-core:jar:3.3.0.RELEASE:compile
[INFO] |     \- org.reactivestreams:reactive-streams:jar:1.0.3:compile

io.netty异常是一个已知的未固定的缺陷。

有办法解决这个问题吗？我已经尝试过以下几种方法：

• lettuce-core的version :相同的异常
• 用过的5.0.5版lettuce-core：Get NoSuchMethodError: NoSuchMethodError

有解决这个问题的办法吗？

Answer 1

bug报告的注释表明这将减轻问题，但并不能完全解决问题。也许下面这样的方法对于您的用例来说已经足够好了？

public class MyServletContextListener implements ServletContextListener {

    public void contextInitialized(ServletContextEvent event) {

    }

    public void contextDestroyed(ServletContextEvent event) {
        io.netty.util.internal.InternalThreadLocalMap.destroy();
    }

}