1. in.readBytes 導(dǎo)致堆外內(nèi)存泄漏
使用netty 中偶現(xiàn) LEAK: ByteBuf.release() was not called before it's garbage-collected. 在幾次檢查自己的代碼胜嗓，發(fā)現(xiàn)ByteBuf都有釋放。就是找不到問(wèn)題冈止，翻閱了一下netty的官方文檔殿如，有兩種方式可以 打印出泄漏的詳細(xì)信息
- ResourceLeakDetector.setLevel(ResourceLeakDetector.Level.ADVANCED);
- -Dio.netty.leakDetectionLevel=advanced
打印日志如下：
io.netty.buffer.AdvancedLeakAwareByteBuf.writeBytes(AdvancedLeakAwareByteBuf.java:600)
io.netty.buffer.AbstractByteBuf.readBytes(AbstractByteBuf.java:829)
com.XXX.XXX.XXX.network.codec.XXXTcpDecoder.decode(XXXTcpDecoder.java:55)
io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:489)
io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:428)
io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:265)
io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1334)
io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:926)
io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:134)
io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:644)
io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:579)
io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:496)
io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:458)
io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:858)
io.netty.util.concurrent.DefaultThreadFactory$DefaultRunnableDecorator.run(DefaultThreadFactory.java:138)
java.lang.Thread.run(Thread.java:748)
Created at:
io.netty.util.ResourceLeakDetector.track(ResourceLeakDetector.java:237)
io.netty.buffer.PooledByteBufAllocator.newDirectBuffer(PooledByteBufAllocator.java:331)
io.netty.buffer.AbstractByteBufAllocator.directBuffer(AbstractByteBufAllocator.java:181)
io.netty.buffer.AbstractByteBufAllocator.buffer(AbstractByteBufAllocator.java:117)
io.netty.buffer.AbstractByteBuf.readBytes(AbstractByteBuf.java:828)
com.XXX.XXX.XXX.network.codec.XXXTcpDecoder.decode(XXXTcpDecoder.java:55)
io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:489)
io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:428)
io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:265)
io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1334)
io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:926)
io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:134)
io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:644)
io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:579)
io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:496)
io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:458)
io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:858)
io.netty.util.concurrent.DefaultThreadFactory$DefaultRunnableDecorator.run(DefaultThreadFactory.java:138)
java.lang.Thread.run(Thread.java:748)
com.XXX.XXX.XXX.network.codec.XXXTcpDecoder.decode(XXXTcpDecoder.java:55
來(lái)看一下這一行明確提示泄漏的地方，然后看了一下對(duì)應(yīng)的代碼一臉懵逼
image.png
in.readBytes 需要釋放bytebuf ？？尊剔？？ 這他媽什么操作 嚇得我趕緊看了一下源代碼菱皆。须误。 注意 我特么也很sb 仔細(xì)看入?yún)?一個(gè)是 long 一個(gè)是 byte[] 導(dǎo)致我浪費(fèi)了很多時(shí)間
@Override
public ByteBuf readBytes(byte[] dst) {
readBytes(dst, 0, dst.length);
return this;
}
沒(méi)毛病啊，非常奇怪仇轻。為啥＞┝ ！Ｅ竦辍＜酪！ 然后就是各種google
加了 ReferenceCountUtil.release(in);
in.readByte();
int dataLength = remaining - 17;
byte[] dataByte = new byte[dataLength];
in.readBytes(dataByte);
String data = new String(dataByte);
in.readBytes(8);
疲陕。方淤。。蹄殃。携茂。
ReferenceCountUtil.release(in);
不但沒(méi)用，鏈接都報(bào)錯(cuò)了Ｗ缪摇；淇唷！７郧鸳谜！
接著開(kāi)始懷疑這個(gè)是不是netty自身的bug。式廷。咐扭。
換了版本還是有問(wèn)題！；稀；确尽！策严！ 受不了Ｋ肽健！Ｆ薜肌９涿唷！
然后繼續(xù)思考人生倔韭。無(wú)意再次點(diǎn)擊看源碼术浪。。突然有一句mmp 不知當(dāng)講不當(dāng)講Ｊ僮谩Ｒ人铡！
@Override
public ByteBuf readBytes(int length) {
checkReadableBytes(length);
if (length == 0) {
return Unpooled.EMPTY_BUFFER;
}
ByteBuf buf = alloc().buffer(length, maxCapacity);
buf.writeBytes(this, readerIndex, length);
readerIndex += length;
return buf;
}
.... readBytes方法返回新的byteBuf 醇疼？硕并？法焰？
image.png
那特么我剛開(kāi)始看是哪個(gè)源碼？倔毙？埃仪？ 然后把整個(gè) AbstractByteBuf 看了一遍
內(nèi)心崩潰 readBytes 方法有很多，每個(gè)入?yún)⒉煌略撸牵卵蛉。。么库。傻丝。。?br>
readBytes(int length) 這個(gè)是返回一個(gè)新的bytebuf 所以需要釋放掉Ｋ呷濉Ｆ乡帧！
弄了半天允睹，還是自己sb运准。從錯(cuò)誤中已經(jīng)明確提示哪一行沒(méi)有釋放，但是結(jié)果還是饒了這么多彎缭受。胁澳。。米者。韭畸。。
