Disruptor RingBuffer-based minimalist NIO HTTP test server

DisruptorTest.java

import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.net.StandardSocketOptions;
import java.nio.ByteBuffer;
import java.nio.channels.CancelledKeyException;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;

import com.lmax.disruptor.AlertException;
import com.lmax.disruptor.BlockingWaitStrategy;
import com.lmax.disruptor.EventFactory;
import com.lmax.disruptor.FatalExceptionHandler;
import com.lmax.disruptor.RingBuffer;
import com.lmax.disruptor.SingleThreadedClaimStrategy;
import com.lmax.disruptor.TimeoutException;
import com.lmax.disruptor.WorkHandler;
import com.lmax.disruptor.WorkerPool;
import com.lmax.disruptor.dsl.Disruptor;

/**
 * @author Jon Brisbin <jon@jbrisbin.com>
 */
public class DisruptorTest {

  @SuppressWarnings({"unchecked"})
  public static void main(String[] args) throws InterruptedException, IOException, AlertException, TimeoutException {
    final int cores = Runtime.getRuntime().availableProcessors();

    Executor executor = Executors.newFixedThreadPool(cores);

    final int bufferSize = 8 * 1024;
    int ringSize = new Double(Math.pow(2, cores + 1)).intValue();

    final RingBuffer<ByteBuffer> bufferRing = new Disruptor<>(
        new EventFactory<ByteBuffer>() {
          @Override public ByteBuffer newInstance() {
            return ByteBuffer.allocate(bufferSize);
          }
        },
        executor,
        new SingleThreadedClaimStrategy(ringSize),
        new BlockingWaitStrategy()
    ).start();

    int handlerCount = cores;
    WorkHandler<SelectionEvent>[] handlers = new WorkHandler[handlerCount];
    for (int i = 0; i < handlerCount; i++) {
      handlers[i] = new WorkHandler<SelectionEvent>() {

        ByteBuffer msg = ByteBuffer.wrap(
            ("HTTP/1.1 200 OK\r\n" +
                "Connection: Keep-Alive\r\n" +
                "Content-Type: text/plain\r\n" +
                "Content-Length: 12\r\n\r\n" +
                "Hello World!").getBytes());

        @Override public void onEvent(SelectionEvent ev) throws Exception {
          // Allocate a ByteBuffer from a RingBuffer
          ByteBuffer buffer = bufferRing.get(ev.bufferId);
          if (buffer.position() > 0) {
            buffer.clear();
          }

          try {
            int read = -1;
            try {
              // Read data from the Channel
              read = ev.channel.read(buffer);
            } catch (IOException e) {
              switch (e.getMessage()) {
                case "Connection reset by peer":
                case "Broken pipe":
                  break;
                default:
                  e.printStackTrace();
              }
            } catch (CancelledKeyException e) {
              ev.channel.close();
            }

            if (read > 0) {
              try {
                // Write the response immediately
                ev.channel.write(msg.duplicate());
              } catch (IOException e) {
                switch (e.getMessage()) {
                  case "Connection reset by peer":
                  case "Broken pipe":
                    break;
                  default:
                    e.printStackTrace();
                }
              } catch (CancelledKeyException e) {
                // Close the channel if something goes wrong
                ev.channel.close();
              }

              // Read the data into memory
              buffer.flip();
              byte[] bytes = new byte[buffer.remaining()];
              buffer.get(bytes);
              //String input = new String(bytes);
            } else {
              ev.key.cancel();
            }
          } finally {
            // Put the ByteBuffer back into the RingBuffer for re-use
            bufferRing.publish(ev.bufferId);
          }
        }
      };
    }

    // Use a WorkerPool for handling requests
    WorkerPool acceptPool = new WorkerPool(
        new EventFactory<SelectionEvent>() {
          @Override public SelectionEvent newInstance() {
            return new SelectionEvent();
          }
        },
        new SingleThreadedClaimStrategy(ringSize),
        new BlockingWaitStrategy(),
        new FatalExceptionHandler(),
        handlers);
    final RingBuffer<SelectionEvent> workerRing = acceptPool.start(executor);

    final ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
    serverSocketChannel.configureBlocking(false);

    final Selector selector = Selector.open();
    serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
    serverSocketChannel.bind(new InetSocketAddress("127.0.0.1", 3000), 1024);

    // Allocate the first worker
    long workerId = workerRing.next();
    while (true) {
      int cnt = 0;
      try {
        cnt = selector.select();
      } catch (CancelledKeyException ignored) {
        // There's a bug on Mac OS X's JVM that might throw a bogus CancelledKeyException
      }
      if (cnt > 0) {
        Iterator<SelectionKey> keys = selector.selectedKeys().iterator();
        while (keys.hasNext()) {
          SelectionKey key = keys.next();
          keys.remove();
          try {
            if (key.isValid()) {
              SelectionEvent event;
              if (key.isAcceptable()) {
                if (serverSocketChannel.isOpen()) {
                  ServerSocket serverSocket = serverSocketChannel.socket();
                  serverSocket.setReceiveBufferSize(bufferSize);
                  serverSocket.setReuseAddress(true);

                  boolean hasSocket = true;
                  while (hasSocket) {
                    SocketChannel channel = serverSocketChannel.accept();
                    if (null != channel) {
                      channel.configureBlocking(false);
                      channel.setOption(StandardSocketOptions.SO_KEEPALIVE, true);
                      channel.setOption(StandardSocketOptions.TCP_NODELAY, true);
                      channel.setOption(StandardSocketOptions.SO_RCVBUF, bufferSize);
                      channel.setOption(StandardSocketOptions.SO_SNDBUF, bufferSize);
                      channel.register(selector, SelectionKey.OP_READ);

                      // Allocate an Event object for dispatching to the handler
                      event = workerRing.get(workerId);
                      event.id = workerId;
                      event.channel = channel;
                      event.selector = selector;
                      event.key = key;
                      event.serverChannel = serverSocketChannel;
                      // Allocate a new ByteBuffer from this thread (since I'm using a SingleThreadedClaimStrategy)
                      event.bufferId = bufferRing.next();
                      // Dispatch this event to a handler
                      workerRing.publish(workerId);
                      // Immediately allocate the next worker ID
                      workerId = workerRing.next();
                    } else {
                      hasSocket = false;
                    }
                  }
                }
              }

              if (key.isReadable() || key.isWritable()) {
                // Allocate an Event object for dispatching to the handler
                event = workerRing.get(workerId);
                event.id = workerId;
                event.channel = (SocketChannel) key.channel();
                event.selector = selector;
                event.key = key;
                event.serverChannel = serverSocketChannel;
                // Allocate a new ByteBuffer from this thread (since I'm using a SingleThreadedClaimStrategy)
                event.bufferId = bufferRing.next();
                // Dispatch this event to a handler
                workerRing.publish(workerId);
                // Immediately allocate the next worker ID
                workerId = workerRing.next();
              }

            }
          } catch (CancelledKeyException e) {
            key.channel().close();
          }
        }
      }

    }
  }

  private static class SelectionEvent {

    Long id;
    Selector selector;
    ServerSocketChannel serverChannel;
    SelectionKey key;
    SocketChannel channel;
    long bufferId = -1L;

    public SelectionEvent() {
    }

  }

}