NIO: multiple selectors

Question

Hi,
How to implement nb server with multiples selectors? I have 3 selectors and 3 corresponding threads. Every selector serve for one type of operation OP_ACCEPT, OP_READ and OP_WRITE. When I receive a new connection and try to register a new channel with other selector the operation blocks on Channel.register(). It works only with the same selector that accepted this connection.
                    if ( key.isAcceptable() ) {
                        // accepting incoming socket connection
                        ServerSocketChannel ssc = (ServerSocketChannel) key.channel();
                             SocketChannel ch = ssc.accept();
                             // registering client
                             ch.configureBlocking( false );
                             ch.socket().setReceiveBufferSize( RECEIVE_BUFFER_SIZE );
                             ch.socket().setSendBufferSize( SEND_BUFFER_SIZE );
                             ch.register( readSelector, SelectionKey.OP_READ );
                        }Is it possible to use various selectors?

Answer 1

Dunno what you've done exactly but Selector.select() does three levels of synchronization which are described in the Javadoc, and SelectableChannel.register() also needs to synchronize on of of those items, i.e. the registered key set.
A separate reading thread can only help if there are multiple processors and the different threads are executing in different processors. I'm dubious about the strategy of separating reading from writing specifically. If I was going to use multiple selectors I would allocate channels to them arbitrarily rather than on the basis of OP_READ/OP_WRITE.