Netty连接抛出StackOverflowException

时间：2019-01-15 15:47:28

标签： java netty

我们最近在生产环境中遇到问题，导致我们的软件停止正常运行。正如您在下面看到的那样，堆栈跟踪中没有显示我们的代码，而只是Netty中的递归调用。发生这种情况时，似乎所有将来的连接都会被拒绝，并且在几个内核上CPU都已用尽。 （不是全部，而是一些），这很奇怪，因为既然所有连接都断开之后就不再有流量，那么到底正在处理什么？

如前所述，这仅在我们的生产环境中发生。尽管当我们每天24小时运行多个实例且连接数达100个时，我们仍会在高峰时段看到此问题的频率更高，尽管我们每天24小时运行多个实例，且连接数为100，而我们每周仍然只能看到此问题2次，因此很遗憾地尝试获取有关这个问题是一个痛苦的过程。我们也有理由相信，当服务器之间的连接不良时，出现此问题的可能性就会增加。

我以前在Netty上工作不多，并且由于大多数不是我的代码，所以我对哪儿去哪儿都不了解，所以寻求帮助将是最好的选择。

这是我们的频道初始化程序中的代码：

    @Override
protected void initChannel(SocketChannel ch) {
    //Final handler in the pipeline. Deals with the objects once and hands them off to the rest of the code
    MessageHandler handler = new MessageHandler(client);
    //Converts the raw bytes into objects that we can deal with
    CodecsHandler codecs = new CodecsHandler(client, ProtocolType.HANDSHAKE.getProtocol());
    //Splits byte streams up into their packets
    FramingHandler framing = new FramingHandler();

    try {
        ch.config().setOption(ChannelOption.IP_TOS, 0x18);
    } catch (ChannelException ex) {
        log.warn("Kernel lacks support for IP_TOS");
    }
    ch.config().setAllocator(PooledByteBufAllocator.DEFAULT);

    ch.pipeline()
            .addLast("idle_timeout", new IdleStateHandler(READ_IDLE_TIMEOUT, WRITE_IDLE_TIMEOUT, 0))
            .addLast("framing", framing)
            //The Noop handler does nothing (These parts of the pipeline are placed later)
            .addLast("compression", NoopHandler.INSTANCE)
            .addLast("codecs", codecs)
            .addLast("handler", handler);
}

这是我们的消息处理程序类：

import com.flowpowered.network.Message;
import com.flowpowered.network.session.Session;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import lombok.extern.slf4j.Slf4j;
import mycode.Client;

import java.util.concurrent.atomic.AtomicReference;

@Slf4j
public final class MessageHandler extends SimpleChannelInboundHandler<Message> {

    private final AtomicReference<Session> session = new AtomicReference<>(null);
    private final Client client;

    public MessageHandler(Client client) {
        this.client = client;
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        Channel c = ctx.channel();
        //Sends some packets packet back to the server and sets the channel object in the client to the channel object above.
        //The returned object is an extended class of https://github.com/OverCaste/flow-networking/blob/master/src/main/java/com/flowpowered/networking/session/Session.java
        Session s = client.newSession(c);
        if (!session.compareAndSet(null, s)) {
            throw new IllegalStateException("Session may not be set more than once");
        }
        s.onReady();
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) {
        Session session = this.session.get();
        if(session != null) {
            session.onDisconnect();
        } else {
            log.warn("Child session was null so could not disconnect");
        }
    }

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, Message i) {
        //Passes the message off to our session object
        session.get().messageReceived(i);
    }

    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt) {

    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        session.get().onInboundThrowable(cause);
    }

    public AtomicReference<Session> getSession() {
        return session;
    }
}

这是我们的编解码器处理程序

import com.flowpowered.network.Codec;
import com.flowpowered.network.Message;
import com.flowpowered.network.util.ByteBufUtils;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.EncoderException;
import io.netty.handler.codec.MessageToMessageCodec;
import lombok.extern.slf4j.Slf4j;
import mycode.Client;
import mycode.CustomProtocol;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.List;

@Slf4j
public final class CodecsHandler extends MessageToMessageCodec<ByteBuf, Message> {

    private final CustomProtocol protocol;
    private final Client client;

    public CodecsHandler(Client client, CustomProtocol protocol) {
        this.protocol = protocol;
        this.client = client;
    }

    @Override
    protected void encode(ChannelHandlerContext ctx, Message msg, List<Object> out) throws Exception {
        // find codec
        Class<? extends Message> clazz = msg.getClass();
        //Codec registration is handled by https://github.com/OverCaste/flow-networking/blob/master/src/main/java/com/flowpowered/networking/Codec.java
        Codec.CodecRegistration reg = protocol.getCodecRegistration(clazz);
        if (reg == null) {
            throw new EncoderException("Unknown message type: " + clazz);
        }

        // write header
        ByteBuf headerBuf = ctx.alloc().buffer(8);
        ByteBufUtils.writeVarInt(headerBuf, reg.getOpcode());

        // write body
        ByteBuf messageBuf = ctx.alloc().buffer();
        messageBuf = reg.getCodec().encode(messageBuf, msg);

        out.add(Unpooled.wrappedBuffer(headerBuf, messageBuf));
    }

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf msg, List<Object> out) throws Exception {
        // find codec and read header
        //https://github.com/OverCaste/flow-networking/blob/master/src/main/java/com/flowpowered/networking/Codec.java
        Codec<?> codec = protocol.newReadHeader(msg);

        // read body
        Message decoded = codec.decode(msg);

        if (msg.readableBytes() > 0) {
            log.warn("Leftover bytes ({}) after decoding: {}", msg.readableBytes(), decoded);
        }

        out.add(decoded);
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        log.error("Codec throwable caught", cause);

        //We do some other stuff around other parts of the code here
    }
}

这是我们的FramingHandler 

import com.flowpowered.network.util.ByteBufUtils;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageCodec;

import java.util.List;

public final class FramingHandler extends ByteToMessageCodec<ByteBuf> {

    private static boolean readableVarInt(ByteBuf buf) {
        if (buf.readableBytes() > 5) {
            // maximum varint size
            return true;
        }

        int idx = buf.readerIndex();
        byte in;
        do {
            if (buf.readableBytes() < 1) {
                buf.readerIndex(idx);
                return false;
            }
            in = buf.readByte();
        } while ((in & 0x80) != 0);

        buf.readerIndex(idx);
        return true;
    }

    @Override
    protected void encode(ChannelHandlerContext ctx, ByteBuf msg, ByteBuf out) {
        ByteBufUtils.writeVarInt(out, msg.readableBytes());
        out.writeBytes(msg);
    }

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
        // check for length field readability
        in.markReaderIndex();
        if (!readableVarInt(in)) {
            return;
        }

        // check for contents readability
        int length = ByteBufUtils.readVarInt(in);
        if (in.readableBytes() < length) {
            in.resetReaderIndex();
            return;
        }

        // read contents into buf
        ByteBuf buf = ctx.alloc().buffer(length);
        in.readBytes(buf, length);
        out.add(buf);
    }
}

这里是压缩处理程序

import com.flowpowered.network.util.ByteBufUtils;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.DecoderException;
import io.netty.handler.codec.EncoderException;
import io.netty.handler.codec.MessageToMessageCodec;

import java.util.List;
import java.util.zip.Deflater;
import java.util.zip.Inflater;

public final class CompressionHandler extends MessageToMessageCodec<ByteBuf, ByteBuf> {

    private static final int MAX_INFLATED_BYTES = 1_000_000;
    private static final int COMPRESSION_LEVEL = Deflater.DEFAULT_COMPRESSION;

    private final int threshold;
    private final Inflater inflater;
    private final Deflater deflater;

    public CompressionHandler(int threshold) {
        this.threshold = threshold;
        inflater = new Inflater();
        deflater = new Deflater(COMPRESSION_LEVEL);
    }

    @Override
    protected void encode(ChannelHandlerContext ctx, ByteBuf msg, List<Object> out) {
        ByteBuf prefixBuf = ctx.alloc().buffer(5);
        ByteBuf contentsBuf;
        try {
            if (msg.readableBytes() >= threshold){
                // message should be compressed
                int index = msg.readerIndex();
                int length = msg.readableBytes();

                byte[] sourceData = new byte[length];
                msg.readBytes(sourceData);
                deflater.setInput(sourceData);
                deflater.finish();

                ByteBuf result = msg.alloc().buffer(length);
                byte[] byteArray = new byte[8192];
                int totalBytes = 0;
                while (!deflater.finished()){
                    int compressedLength = deflater.deflate(byteArray);
                    result.writeBytes(byteArray, 0, compressedLength);
                    totalBytes += compressedLength;
                }
                deflater.reset();

                if (totalBytes == 0){
                    // compression failed in some weird way
                    throw new EncoderException("Failed to compress message of size " + length);
                } else if (totalBytes >= length){
                    // compression increased the size. threshold is probably too low
                    // send as an uncompressed packet
                    result.release();
                    ByteBufUtils.writeVarInt(prefixBuf, 0);
                    msg.readerIndex(index);
                    msg.retain();
                    contentsBuf = msg;
                } else {
                    // all is well
                    ByteBufUtils.writeVarInt(prefixBuf, length);
                    contentsBuf = result;
                }
            } else {
                // message should be sent through
                ByteBufUtils.writeVarInt(prefixBuf, 0);
                msg.retain();
                contentsBuf = msg;
            }
        } catch (Exception e){
            prefixBuf.release();
            throw e;
        }

        out.add(Unpooled.wrappedBuffer(prefixBuf, contentsBuf));
    }

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf msg, List<Object> out) throws Exception {
        int index = msg.readerIndex();
        int uncompressedSize = ByteBufUtils.readVarInt(msg);
        if (uncompressedSize == 0) {
            // message is uncompressed
            int length = msg.readableBytes();
            if (length >= threshold) {
                // invalid
                throw new DecoderException("Received uncompressed message of size " + length + " greater than threshold " + threshold);
            }

            msg.retain();
            out.add(msg);
        } else {
            if (uncompressedSize > MAX_INFLATED_BYTES)
                //Don't trust this - this is a very big and may come with malicious intent
                throw new DecoderException("Resulting uncompressed size is too large for us to handle safely");
            // message is compressed
            byte[] sourceData = new byte[msg.readableBytes()];
            msg.readBytes(sourceData);
            inflater.setInput(sourceData);

            byte[] destData = new byte[8192];
            ByteBuf result = msg.alloc().buffer(uncompressedSize);
            int totalBytes = 0;
            while (!inflater.finished()){
                int resultLength = inflater.inflate(destData);
                result.writeBytes(destData, 0, resultLength);
                totalBytes += resultLength;
                if (totalBytes > uncompressedSize)
                    throw new DecoderException("Received compressed message claiming to be of size " + uncompressedSize + " but actually larger");
            }
            inflater.reset();

            if (totalBytes == 0) {
                // might be a leftover from before compression was enabled (no compression header)
                // uncompressedSize is likely to be < threshold
                result.release();
                msg.readerIndex(index);
                msg.retain();
                out.add(msg);
            } else if (totalBytes != uncompressedSize) {
                throw new DecoderException("Received compressed message claiming to be of size " + uncompressedSize + " but actually " + totalBytes);
            } else {
                out.add(result);
            }
        }
    }
}

这是我们的NoopH​​andler（实际上，它只是作为管道中尚未执行任何操作的部分的占位符）

import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerAdapter;

@ChannelHandler.Sharable
public class NoopHandler extends ChannelHandlerAdapter {

    public static final NoopHandler INSTANCE = new NoopHandler();

    private NoopHandler() {}
}

由于该项目的规模以及不允许发布所有代码的事实，我去除了很多不必要的代码和重构的类名。

https://pastebin.com/RAp1qcxb 

java.lang.StackOverflowError: null
at org.apache.logging.slf4j.Log4jLogger.log(Log4jLogger.java:371) ~[log4j-slf4j-impl-2.11.1.jar:2.11.1]
at io.netty.util.internal.logging.LocationAwareSlf4JLogger.log(LocationAwareSlf4JLogger.java:42) ~[netty-common-4.1.31.Final.jar:4.1.31.Final]
at io.netty.util.internal.logging.LocationAwareSlf4JLogger.warn(LocationAwareSlf4JLogger.java:198) ~[netty-common-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:294) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.notifyHandlerException(AbstractChannelHandlerContext.java:856) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:778) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:768) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:770) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.ChannelDuplexHandler.flush(ChannelDuplexHandler.java:117) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:776) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:768) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:770) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.ChannelDuplexHandler.flush(ChannelDuplexHandler.java:117) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:776) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:768) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:770) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.ChannelDuplexHandler.flush(ChannelDuplexHandler.java:117) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:776) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:768) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:770) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.ChannelDuplexHandler.flush(ChannelDuplexHandler.java:117) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:776) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:768) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:770) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.ChannelDuplexHandler.flush(ChannelDuplexHandler.java:117) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:776) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:768) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:770) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.ChannelDuplexHandler.flush(ChannelDuplexHandler.java:117) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:776) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:768) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:770) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.ChannelDuplexHandler.flush(ChannelDuplexHandler.java:117) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:776) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:768) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:770) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.ChannelDuplexHandler.flush(ChannelDuplexHandler.java:117) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:776) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:768) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:770) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.ChannelDuplexHandler.flush(ChannelDuplexHandler.java:117) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:776) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:768) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:770) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.ChannelDuplexHandler.flush(ChannelDuplexHandler.java:117) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:776) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:768) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:770) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.ChannelDuplexHandler.flush(ChannelDuplexHandler.java:117) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:776) ~[netty-transport-4.1.31.Final.jar:4.1.31.Final]
... ... ...

1 个答案:

答案 0 :(得分：1)

这是正在发生的事情的踪迹，最终看来findContextOutbound()最终返回了从一开始就调用AbstractChannelHandlerContext的同一flush()实例，并重复调用{{1} }。您可能需要调试并逐步完成这些方法，或者调查flush()发生的设置。

ChannelHandlerContext
Cycle:
    [repeat from 1] at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749)
    [6] at io.netty.channel.ChannelDuplexHandler.flush(ChannelDuplexHandler.java:117)
    [5] at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:776)
    [4] at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:768)
    [3] at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749)
    [2] at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:770)
    [1] at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749)

[1] AbstractChannelHandlerContext.flush():

      final AbstractChannelHandlerContext next = findContextOutbound(); // see following method
      EventExecutor executor = next.executor();
      if (executor.inEventLoop()){
          next.invokeFlush() // -> [2]
      } else { /* threadded invokeFlush */ }

    // do you happen to have two AbstractChannelHandlerContexts ctx1 and ctx2, such that?:
    //     ctx1.prev == ctx2 && ctx2.prev == ctx1;
    AbstractChannelHandlerContext.findContextOutbound():

      AbstractChannelHandlerContext ctx = this;
      do {
          ctx = ctx.prev;
      } while (!ctx.outbound);
      return ctx;

[2] AbstractChannelHandlerContext.invokeFlush():

      // this time invokeHandler() returns `false`
      if (invokeHandler()){
          invokeFlush0();
      }  else {
          flush(); // -> [3]
      }

    /**
     * Makes best possible effort to detect if `ChannelHandler.handlerAdded(ChannelHandlerContext)`
     * was called yet. If not return `false` and if called or could not detect return `true`.
     *
     * If this method returns `false` we will not invoke the `ChannelHandler` but just forward the event.
     * This is needed as `DefaultChannelPipeline` may already put the `ChannelHandler` in the linked-list
     * but not called `ChannelHandler.handlerAdded(ChannelHandlerContext)`.
     */
    AbstractChannelHandlerContext.invokeHandler():

      int handlerState = this.handlerState;
      return handlerState == ADD_COMPLETE || (!ordered && handlerState == ADD_PENDING);

[3] AbstractChannelHandlerContext.flush():

      final AbstractChannelHandlerContext next = findContextOutbound();
      EventExecutor executor = next.executor();
      if (executor.inEventLoop())
         next.invokeFlush() // -> [4]
      } else { /* threadded invokeFlush */ }

[4] AbstractChannelHandlerContext.invokeFlush():

      // this time invokeHandler() returns `true`
      if (invokeHandler()){
          invokeFlush0(); // -> [5]
      }  else {
         flush();
      }

[5] AbstractChannelHandlerContext.invokeFlush0():

      try {
          ((ChannelOutboundHandler) handler()).flush(this); // -> [6]
      } catch (Throwable t) {
          notifyHandlerException(t); // ultimately reaches this when `StackOverflowException`
      }
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