Netty only writes after read complete

[DSeeLP]

I want to cache all outgoing buffers and reuse them if a request is replayed. The problem is that netty only starts writing after the read is complete. I want to only decode the message once and then simply reply with the cached response.
But in the moment it looks like this:

Read and Decode
Read and Decode
Read and Decode
Read Complete
Write Not cached
Write Not cached
Write Not cached

But i want it to look like this:

Read and Decode
Write and cache buffer
Read
Write cached
Read
Write cached
Read Complete

Edit: The reply is cached in a seperate ChannelOutboundHandler.

[normanmaurer]

@DSeeLP please show the ChannelOuttboundHandler code and also your whole pipeline setup.

[DSeeLP]

Here is my Pipeline Setup: https://gist.github.com/DSeeLP/b68f8616eb3f49143f4a0f4ba02148c8
And i forgot that i was using an MessageToMessageEncoder<PacketResponse> instead of an ChannelOutboundHandler

[normanmaurer]

Replace ctx.write(...) with ctx.writeAndFlush(....). This should do the trick

[DSeeLP]

I found the problem i was using coroutines in my PacketHandler.

This is the code which caused my problem:

            runBlocking {
                context.channel.coroutineScope.launch {
                    context.handle()
                }.join()
            }

launch executes the write on a different thread so the writeAndFlush() in my PacketHandler was executed on a different Thread.

When i removed the launch and used context.handle() directly in runBlocking it worked.

But now after some packets have been processed i get an io.netty.util.IllegalReferenceCountException: refCnt: 0
So what would be the best way to cache bytebufs and later send them.
The log: https://gist.github.com/DSeeLP/5f5e9b85fc56d1727777e324e15dac3d

Edit: The exception in the log occurs when using ctx.writeAndFlush(byteBuf.copy())
This is the exception when supplying the bytebuf directly:

März 29, 2022 11:03:07 AM io.netty.util.ReferenceCountUtil safeRelease
WARNUNG: Failed to release a message: UnpooledDuplicatedByteBuf(freed)
io.netty.util.IllegalReferenceCountException: refCnt: 0, decrement: 1
	at io.netty.util.internal.ReferenceCountUpdater.toLiveRealRefCnt(ReferenceCountUpdater.java:74)
	at io.netty.util.internal.ReferenceCountUpdater.release(ReferenceCountUpdater.java:138)
	at io.netty.buffer.AbstractReferenceCountedByteBuf.release(AbstractReferenceCountedByteBuf.java:100)
	at io.netty.buffer.AbstractDerivedByteBuf.release0(AbstractDerivedByteBuf.java:98)
	at io.netty.buffer.AbstractDerivedByteBuf.release(AbstractDerivedByteBuf.java:94)
	at io.netty.util.ReferenceCountUtil.release(ReferenceCountUtil.java:90)
	at io.netty.util.ReferenceCountUtil.safeRelease(ReferenceCountUtil.java:116)
	at io.netty.channel.ChannelOutboundBuffer.remove0(ChannelOutboundBuffer.java:306)
	at io.netty.channel.ChannelOutboundBuffer.failFlushed(ChannelOutboundBuffer.java:660)
	at io.netty.channel.AbstractChannel$AbstractUnsafe.closeOutboundBufferForShutdown(AbstractChannel.java:672)
	at io.netty.channel.AbstractChannel$AbstractUnsafe.shutdownOutput(AbstractChannel.java:666)
	at io.netty.channel.AbstractChannel$AbstractUnsafe.handleWriteError(AbstractChannel.java:953)
	at io.netty.channel.AbstractChannel$AbstractUnsafe.flush0(AbstractChannel.java:933)
	at io.netty.channel.epoll.AbstractEpollChannel$AbstractEpollUnsafe.flush0(AbstractEpollChannel.java:557)
	at io.netty.channel.AbstractChannel$AbstractUnsafe.flush(AbstractChannel.java:895)
	at io.netty.channel.DefaultChannelPipeline$HeadContext.flush(DefaultChannelPipeline.java:1372)
	at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:750)
	at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:742)
	at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:728)
	at io.netty.channel.ChannelDuplexHandler.flush(ChannelDuplexHandler.java:127)
	at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:750)
	at io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:765)
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:790)
	at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:758)
	at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:808)
	at utils.codec.encoding.ResponseHandler.channelRead(ResponseHandler.kt:47)

[DSeeLP]

I figured everything out thank you.