Disruptor RingBuffer-based simplistic 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.ReadableByteChannel;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.channels.WritableByteChannel;
import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.BlockingDeque;
import java.util.concurrent.ConcurrentSkipListMap;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;
import java.util.concurrent.LinkedBlockingDeque;

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.Sequence;
import com.lmax.disruptor.SingleThreadedClaimStrategy;
import com.lmax.disruptor.TimeoutException;
import com.lmax.disruptor.WorkHandler;
import com.lmax.disruptor.WorkerPool;

/**
 * @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();
    final int bufferSize = 4 * 1024;
    final int ringSize = 2048;
    Executor executor = Executors.newFixedThreadPool(cores);

    final BlockingDeque<ByteBuffer> bufferPool = new LinkedBlockingDeque<>(ringSize);
    for (int i = 0; i < ringSize; i++) {
      bufferPool.add(ByteBuffer.allocate(bufferSize));
    }

    final Map<Long, SocketChannel> channels = new ConcurrentSkipListMap<>();
    final Map<Long, SelectionKey> selectionKeys = new ConcurrentSkipListMap<>();

    int handlerCount = cores;
    WorkHandler<SelectionEvent>[] handlers = new WorkHandler[handlerCount];
    final Sequence[] sequences = new Sequence[handlerCount];
    for (int i = 0; i < handlerCount; i++) {
      final int handlerId = 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());
        Sequence sequence = new Sequence(-1);

        {
          sequences[handlerId] = sequence;
        }

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

          SocketChannel channel = channels.get(ev.id);
          SelectionKey key = selectionKeys.get(ev.id);

          try {
            int read = safeRead(channel, buffer);
            while (read > 0) {
              safeWrite(channel, msg.duplicate());

              // Read the data into memory
              buffer.flip();
              byte[] bytes = new byte[buffer.remaining()];
              buffer.get(bytes);
              //String input = new String(bytes);
              buffer.clear();
              read = safeRead(channel, buffer);
            }
            if (read < 0) {
              key.cancel();
              selectionKeys.remove(ev.id);
            }
          } finally {
            // Put the ByteBuffer back into the RingBuffer for re-use
            bufferPool.add(buffer);
            sequence.set(ev.id);
          }
        }
      };
    }

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

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

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

    // Allocate the first worker
    long workerId = workerRing.next();
    while (true) {
      int cnt = 0;
      try {
        cnt = selector.select();
      } catch (CancelledKeyException e) {}
      if (cnt > 0) {
        Iterator<SelectionKey> keys = selector.selectedKeys().iterator();
        while (keys.hasNext()) {
          SelectionKey key = keys.next();
          keys.remove();
          if (key.isValid()) {
            SelectionEvent event;
            if (key.isAcceptable()) {
              ServerSocket serverSocket = serverSocketChannel.socket();
              serverSocket.setReceiveBufferSize(bufferSize);
              serverSocket.setReuseAddress(true);

              boolean hasSocket = true;
              do {
                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);
                  SelectionKey readKey = channel.register(selector, SelectionKey.OP_READ);

                  // Allocate an Event object for dispatching to the handler
                  event = workerRing.get(workerId);
                  event.id = workerId;
                  channels.put(workerId, channel);
                  selectionKeys.put(workerId, readKey);
                  // Dispatch this event to a handler
                  workerRing.publish(workerId);
                  // Immediately allocate the next worker ID
                  workerId = workerRing.next();
                } else {
                  hasSocket = false;
                }
              } while (hasSocket);
            } else if (key.isReadable()) {
              // Allocate an Event object for dispatching to the handler
              event = workerRing.get(workerId);
              event.id = workerId;
              channels.put(workerId, (SocketChannel) key.channel());
              selectionKeys.put(workerId, key);
              // Dispatch this event to a handler
              workerRing.publish(workerId);
              // Immediately allocate the next worker ID
              workerId = workerRing.next();
            }
          }
        }
      }
    }
  }

  static int safeRead(ReadableByteChannel channel, ByteBuffer dst) throws IOException {
    int read = -1;
    try {
      // Read data from the Channel
      read = channel.read(dst);
    } catch (IOException e) {
      switch ("" + e.getMessage()) {
        case "null":
        case "Connection reset by peer":
        case "Broken pipe":
          break;
        default:
          e.printStackTrace();
      }
      channel.close();
    } catch (CancelledKeyException e) {
      channel.close();
    }
    return read;
  }

  static int safeWrite(WritableByteChannel channel, ByteBuffer src) throws IOException {
    int written = -1;
    try {
      // Write the response immediately
      written = channel.write(src);
    } catch (IOException e) {
      switch ("" + e.getMessage()) {
        case "null":
        case "Connection reset by peer":
        case "Broken pipe":
          break;
        default:
          e.printStackTrace();
      }
      channel.close();
    } catch (CancelledKeyException e) {
      channel.close();
    }
    return written;
  }

  static class SelectionEvent {

    Long id;

    public SelectionEvent() {
    }

  }

}