Netty Splice operation not working in channelRead

Question

• I am using Splice Operation to transfer data from one inbound channel to outbound channel and vice versa using Splice operation to improve performance.
• Inbound channel is between client and proxy service and outbound channel is between proxy and backend service.
• Data should be transferred in channelRead() using Splice operation and not in channelActive() because we need to resolve target server address in channelRead() of 1 handler.
• We don't know the target server address at channel setup time and is based on request contents

itself, thats why its being done in channelRead()

Issue is Splice operation only works in channelActive() but when used in channelRead(), the operation gets stuck and request doesn't go to target server

This is my code

            if (useSplice) {
                 final EpollSocketChannel source = (EpollSocketChannel) ctx.channel();
                 final EpollSocketChannel destination = (EpollSocketChannel) outboundChannel;
     
                 source.config().setAutoRead(false);
     
                 source.eventLoop().execute(() -> source.spliceTo(destination, Integer.MAX_VALUE)
                         .addListener((ChannelFutureListener) future -> {
                             if (!future.isSuccess()) {
                                 future.channel().close();
                             }
                         }));
     
                 source.config().setAutoRead(true);
            }

If I add writeAndFlush() after splice operation, it unblocks the splice operation and server doesn't hang. There are also very good performance improvements observed after this.

         outboundChannel.writeAndFlush(msg).addListener((ChannelFutureListener) future -> {
                 if (future.isSuccess()) {
                     // was able to flush out data, start to read the next chunk
                 ctx.channel().read();
             } else {
                 log.error("Failed writing data.", future.cause());
                 future.channel().close();
             }
         });

Question:

• Is this the expected way to use splice in channelRead()
• Can splice be used in the middle of handler chain?

I on on Netty 4.1 and using JDK 11