I have a Netty ChannelInboundHandler in which I'm making calls to an external service (which is relatively slow). Depending upon the result of that call, I'm rewriting the pipeline to invoke different subsequent handlers. I have this working using a different executor group for the handler, but that's still inefficient, since the handler thread is doing nothing while waiting for the external service to respond.
Complicating the issue is that I'm doing this from a derivative of the PortUnificationServerHandler (itself a derivative of ByteToMessageDecoder), since the external service looks at the SNI hostname to determine whether or not to insert a SslHandler and decode or just to pass the traffic along straight.
I've seen how the HexDumpProxy example makes a call to an external service, but I don't see how this can be done from within something like ByteToMessageDecoder. My rough idea is to create a future for the external request, then have the futures call ChannelHandlerContext.fireUserEventTriggered on completion with a custom event that my handler can look for and do the pipeline rewrites. But that feels ugly, and tests didn't make it look like my event would reach my own handler...
Suggestions?