Netty 4 io.netty.channel.PartialFlushException 写入后

Question

第二次 .write 在我的代码中的新通道上，写入操作的ChannelFuture.isSuccess 为假，ChannelFuture.cause 为io.netty.channel.PartialFlushException: 0 out of 1 message(s) flushed。我不知道应该做些什么来避免这种情况，以及在哪里寻找更深层次的根本原因。

ChannelFuture.cause.getStackTraceString 是：

io.netty.channel.ChannelOutboundMessageHandlerAdapter.flush(ChannelOutboundMessageHandlerAdapter.java:118) io.netty.channel.CombinedChannelDuplexHandler.flush(CombinedChannelDuplexHandler.java:237) io.netty.channel.DefaultChannelHandlerContext.invokeFlush0(DefaultChannelHandlerContext.java:1308) io.netty.channel.DefaultChannelHandlerContext.write0(DefaultChannelHandlerContext.java:1445) io.netty.channel.DefaultChannelHandlerContext.write(DefaultChannelHandlerContext.java:1412) io.netty.channel.DefaultChannelHandlerContext.write(DefaultChannelHandlerContext.java:1034) io.netty.channel.DefaultChannelPipeline.write(DefaultChannelPipeline.java:959) io.netty.channel.AbstractChannel.write(AbstractChannel.java:246) pipe.Broker$writer$.write(Broker.scala:72) pipe.Broker$httpClientHandler.messageReceived(Broker.scala:57) pipe.Broker$httpClientHandler.messageReceived(Broker.scala:52) io.netty.channel.ChannelInboundMessageHandlerAdapter.inboundBufferUpdated(ChannelInboundMessageHandlerAdapter.java:104) io.netty.channel.DefaultChannelHandlerContext.invokeInboundBufferUpdated(DefaultChannelHandlerContext.java:951) io.netty.channel.DefaultChannelHandlerContext.fireInboundBufferUpdated0(DefaultChannelHandlerContext.java:926) io.netty.channel.DefaultChannelHandlerContext.fireInboundBufferUpdated(DefaultChannelHandlerContext.java:904) io.netty.handler.codec.ReplayingDecoder.callDecode(ReplayingDecoder.java:466) io.netty.handler.codec.ByteToMessageDecoder.inboundBufferUpdated(ByteToMessageDecoder.java:69) io.netty.channel.ChannelInboundByteHandlerAdapter.inboundBufferUpdated(ChannelInboundByteHandlerAdapter.java:51) io.netty.channel.CombinedChannelDuplexHandler.inboundBufferUpdated(CombinedChannelDuplexHandler.java:194) io.netty.channel.DefaultChannelHandlerContext.invokeInboundBufferUpdated(DefaultChannelHandlerContext.java:951) io.netty.channel.DefaultChannelHandlerContext.fireInboundBufferUpdated0(DefaultChannelHandlerContext.java:926) io.netty.channel.DefaultChannelHandlerContext.fireInboundBufferUpdated(DefaultChannelHandlerContext.java:904) io.netty.channel.DefaultChannelPipeline.fireInboundBufferUpdated(DefaultChannelPipeline.java:909) io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:115) io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:401) io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:365) io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:302) io.netty.channel.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:110) java.lang.Thread.run(未知来源)

通道上的第一个 .write 运行良好（isSuccess 为真，并且确实写入的消息完美地到达并在其目的地解析）。但是第二个 .write 始终如前所述失败。

第二个 .write 是从我重写的 ChannelInboundMessageHandlerAdapter.messageReceived 方法中发出的，一旦它收到远程对等方收到第一个 .write 的确认。

我执行实际写入的代码（这是 Scala）是：

 request = new DefaultHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.GET, "/"+msg)
              var writeFuture = channel.write(request).addListener(new ChannelFutureListener(){
                  def operationComplete(channelFuture: ChannelFuture){
                    if (channelFuture.isSuccess)
                        println("write finished successfully")
                    else 
                        println ("write failed: " + channelFuture.cause + "\n" + channelFuture.cause.getStackTraceString)
                  }
              })

可能是什么问题，应该如何追踪？

Answer 1

PartialFlushException 包含刷新失败的实际原因。您可以使用 Java 提供的Exception.getCause() 方法获取它：

PartialFlushException e = ...;
e.getCause(); // This will return the exception you raised.

要获取异常的完整信息，而不是打印异常，您必须调用printStackTrace()。

future.cause.printStackTrace()

有关链式异常的更多信息，请参阅this tutorial。