netty LEAK: ByteBuf.release() was not called before it's garbage-collected

背景、netty抛出完整的error信息如下：

2018-02-08 14:30:43.098 [nioEventLoopGroup-5-1] ERROR io.netty.util.ResourceLeakDetector:176 - LEAK: ByteBuf.release() was not called before it's garbage-collected. Enable advanced leak reporting to find out where the leak occurred. To enable advanced leak reporting, specify the JVM option '-Dio.netty.leakDetection.level=advanced' or call ResourceLeakDetector.setLevel() See http://netty.io/wiki/reference-counted-objects.html for more information.

一、结论很直观：内存泄露了

再读读提示：获取更多的信息有两种方法

1. 增加启动jvm参数-Dio.netty.leakDetection.level=advanced

java -jar -Dio.netty.leakDetection.level=advanced your-server.jar

或者

java -jar -Dio.netty.leakDetectionLevel=ADVANCED your-server.jar 

2. 在程序启动时增加相关日志信息

...省略代码...
try {
                    ServerBootstrap sbs = new ServerBootstrap().group(bossGroup, workerGroup)
                            .channel(NioServerSocketChannel.class).handler(new LoggingHandler(LogLevel.INFO))
                            .localAddress(new InetSocketAddress(port))
                            .childHandler(new ChannelInitializer<SocketChannel>() {
                                protected void initChannel(SocketChannel ch) throws Exception {
                                    ch.pipeline().addLast(new IdleStateHandler(10, 0, 0, TimeUnit.SECONDS));
                                    ch.pipeline().addLast(idleStateTrigger);
                                    ch.pipeline().addLast("decoder", new MessageDecoder());
                                    ch.pipeline().addLast("encoder", new MessageEncoder());
                                    ch.pipeline().addLast(serverHandler);
                                };

                            }).option(ChannelOption.SO_BACKLOG, 128).childOption(ChannelOption.SO_KEEPALIVE, true);
                    ResourceLeakDetector.setLevel(ResourceLeakDetector.Level.ADVANCED);
                    ChannelFuture future = sbs.bind(port).sync();
...省略代码...

二、这两种方式都能跟踪到内存泄露时的更多的抛出信息

Recent access records: 2
#2:
io.netty.buffer.AdvancedLeakAwareByteBuf.readBytes(AdvancedLeakAwareByteBuf.java:498)
io.netty.buffer.ByteBufInputStream.read(ByteBufInputStream.java:179)
com.esotericsoftware.kryo.io.Input.fill(Input.java:164)
com.esotericsoftware.kryo.io.Input.require(Input.java:196)
com.esotericsoftware.kryo.io.Input.readVarInt(Input.java:373)
com.esotericsoftware.kryo.util.DefaultClassResolver.readClass(DefaultClassResolver.java:127)
com.esotericsoftware.kryo.Kryo.readClass(Kryo.java:693)
com.esotericsoftware.kryo.Kryo.readClassAndObject(Kryo.java:804)
com.your.package.base.serialize.KryoSerializer.deserialize(KryoSerializer.java:54)
com.your.package.base.link.MessageDecoder.decode(MessageDecoder.java:53)
io.netty.handler.codec.LengthFieldBasedFrameDecoder.decode(...)

三、解决问题

分析日志，建议从自己的代码入手，然后将造成内存泄露的ByteBuf手动释放。

ReferenceCountUtil.release(byteBuf);