order

This article mainly studies dubbo's All Dispatcher.

Dispatcher

dubbo-2.7.3/dubbo-remoting/dubbo-remoting-api/src/main/java/org/apache/dubbo/remoting/Dispatcher.java

@SPI(AllDispatcher.NAME)
public interface Dispatcher {

    /**
     * dispatch the message to threadpool.
     *
     * @param handler
     * @param url
     * @return channel handler
     */
    @Adaptive({Constants.DISPATCHER_KEY, "dispather", "channel.handler"})
    // The last two parameters are reserved for compatibility with the old configuration
    ChannelHandler dispatch(ChannelHandler handler, URL url);

}

• The Dispatcher interface defines the dispatch method and returns the ChannelHandler

AllDispatcher

dubbo-2.7.3/dubbo-remoting/dubbo-remoting-api/src/main/java/org/apache/dubbo/remoting/transport/dispatcher/all/AllDispatcher.java

public class AllDispatcher implements Dispatcher {

    public static final String NAME = "all";

    @Override
    public ChannelHandler dispatch(ChannelHandler handler, URL url) {
        return new AllChannelHandler(handler, url);
    }

}

• AllDispatcher implements the Dispatcher interface, and its dispatch method returns AllChannelHandler

AllChannelHandler

dubbo-2.7.3/dubbo-remoting/dubbo-remoting-api/src/main/java/org/apache/dubbo/remoting/transport/dispatcher/all/AllChannelHandler.java

public class AllChannelHandler extends WrappedChannelHandler {

    public AllChannelHandler(ChannelHandler handler, URL url) {
        super(handler, url);
    }

    @Override
    public void connected(Channel channel) throws RemotingException {
        ExecutorService executor = getExecutorService();
        try {
            executor.execute(new ChannelEventRunnable(channel, handler, ChannelState.CONNECTED));
        } catch (Throwable t) {
            throw new ExecutionException("connect event", channel, getClass() + " error when process connected event .", t);
        }
    }

    @Override
    public void disconnected(Channel channel) throws RemotingException {
        ExecutorService executor = getExecutorService();
        try {
            executor.execute(new ChannelEventRunnable(channel, handler, ChannelState.DISCONNECTED));
        } catch (Throwable t) {
            throw new ExecutionException("disconnect event", channel, getClass() + " error when process disconnected event .", t);
        }
    }

    @Override
    public void received(Channel channel, Object message) throws RemotingException {
        ExecutorService executor = getExecutorService();
        try {
            executor.execute(new ChannelEventRunnable(channel, handler, ChannelState.RECEIVED, message));
        } catch (Throwable t) {
            //TODO A temporary solution to the problem that the exception information can not be sent to the opposite end after the thread pool is full. Need a refactoring
            //fix The thread pool is full, refuses to call, does not return, and causes the consumer to wait for time out
        	if(message instanceof Request && t instanceof RejectedExecutionException){
        		Request request = (Request)message;
        		if(request.isTwoWay()){
        			String msg = "Server side(" + url.getIp() + "," + url.getPort() + ") threadpool is exhausted ,detail msg:" + t.getMessage();
        			Response response = new Response(request.getId(), request.getVersion());
        			response.setStatus(Response.SERVER_THREADPOOL_EXHAUSTED_ERROR);
        			response.setErrorMessage(msg);
        			channel.send(response);
        			return;
        		}
        	}
            throw new ExecutionException(message, channel, getClass() + " error when process received event .", t);
        }
    }

    @Override
    public void caught(Channel channel, Throwable exception) throws RemotingException {
        ExecutorService executor = getExecutorService();
        try {
            executor.execute(new ChannelEventRunnable(channel, handler, ChannelState.CAUGHT, exception));
        } catch (Throwable t) {
            throw new ExecutionException("caught event", channel, getClass() + " error when process caught event .", t);
        }
    }
}

• AllChannelHandler inherits the WrappedChannelHandler, which connects, dis connected, received, caught all get the thread pool through the parent class getExecutorService, and then execute the created ChannelEventRunnable; the receive method is RejectedExecutionException when the exception is caught and the message is Request, and the request is tWhen woWay returns SERVER_THREADPOOL_EXHAUSTED_ERROR

Summary

• The Dispatcher interface defines the dispatch method and returns the ChannelHandler
• AllChannelHandler inherits the WrappedChannelHandler, whose connected, disconnected, received, caught all obtain the thread pool through the parent getExecutorService, and then execute the created ChannelEventRunnable
• The received method of AllChannelHandler returns SERVER_THREADPOOL_EXHAUSTED_ERROR when it catches an exception, the message is Request, and the request is twoWay

doc

• AllDispatcher