synchronous client send/rcv help

[Jason Ward]

I'm looking for some advice on a good design for the following problem.

I have a need to perform an app-level handshake once the channel is 
connected. I've implemented this via a handshake method call fired from 
the channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e) of 
my IoHandler (extending SimpleChannelUpstreamHandler).

The crux of the issue is a need for this app-level handshake to occur 
synchronously blocking each subsequent send (in the handshake) until a 
previous response from the peer is rcvd and validated. I've found that 
blocking during my handshake method in fact blocks the I/O thread 
altogether. I can see the peer actually receives the req and sends a 
response, but a corresponding messageReceived(ChannelHandlerContext ctx, 
MessageEvent e) isn't fired until after my originating caller times 
out... which just so happens to initiate a disconnect and disposal of 
resources as well.

I can easily workaround this issue by chaining messageReceived 
callbacks, but I'm looking for a more elegant solution. Does anyone have 
advice on how I can pull this off? Is there any example of how to force 
only some requests to be blocking? I've seen the thread on the forum 
where Trustin indicates adding a LinkedBlockingQueue is a solution, but 
the original poster's use-case is quite different from mine in that all 
requests needed to be blocking, and as best I understand it, I'm 
effectively doing the same thing but creating a problem because I'm 
calling my blocking method from channelConnected()... altho I might be 
totally wrong.


Any advice is greatly appreciated.


Note : Because this might be a simple problem with my I/O thread pools, 
I'll include my client code here (only slightly redacted for protected 
info).

            ClientSocketChannelFactory factory = new 
NioClientSocketChannelFactory(
                    Executors.newCachedThreadPool(new 
NamedThreadFactory("NioClientSocketChannelFactoryBoss_"+name)),
                    Executors.newCachedThreadPool(new 
NamedThreadFactory("NioClientSocketChannelFactory_"+name))
            );
            bootstrap = new ClientBootstrap(factory);
            bootstrap.setOption("tcpNoDelay", true);
            bootstrap.setOption("keepAlive", true);

            OrderedMemoryAwareThreadPoolExecutor threadPool = new 
OrderedMemoryAwareThreadPoolExecutor(
                    corePoolSize, 0, 0, keepAliveTime, TimeUnit.SECONDS, 
new NamedThreadFactory("XXX"+name));

            ChannelPipeline pipeline = bootstrap.getPipeline();
            pipeline.addLast("exec", new ExecutionHandler(threadPool));
            pipeline.addLast("decoder", new AsyncMSGIoDecoder());
            pipeline.addLast("encoder", new AsyncMSGIoEncoder());
            pipeline.addLast("handler", new MSGIoHandler(this));

            channelFuture = bootstrap.connect(new 
InetSocketAddress(host, port));


Thanks in advance,
JW