Ongoing work on #74 introduced better abstractions in reactor - tcp and udp mode

reactor/src/main/java/com/iluwatar/reactor/AbstractNioChannel.java

@@ -0,0 +1,75 @@
+package com.iluwatar.reactor;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.channels.SelectableChannel;
+import java.nio.channels.SelectionKey;
+import java.util.Map;
+import java.util.Queue;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentLinkedQueue;
+
+public abstract class AbstractNioChannel {
+	
+	private SelectableChannel channel;
+	private ChannelHandler handler;
+	private Map<SelectableChannel, Queue<ByteBuffer>> channelToPendingWrites = new ConcurrentHashMap<>();
+	private NioReactor reactor;
+	
+	public AbstractNioChannel(ChannelHandler handler, SelectableChannel channel) {
+		this.handler = handler;
+		this.channel = channel;
+	}
+	
+	public void setReactor(NioReactor reactor) {
+		this.reactor = reactor;
+	}
+
+	public SelectableChannel getChannel() {
+		return channel;
+	}
+
+	public abstract int getInterestedOps();
+
+	public abstract ByteBuffer read(SelectionKey key) throws IOException;
+
+	public void setHandler(ChannelHandler handler) {
+		this.handler = handler;
+	}
+	
+	public ChannelHandler getHandler() {
+		return handler;
+	}
+
+	// Called from the context of reactor thread
+	public void write(SelectionKey key) throws IOException {
+		Queue<ByteBuffer> pendingWrites = channelToPendingWrites.get(key.channel());
+		while (true) {
+			ByteBuffer pendingWrite = pendingWrites.poll();
+			if (pendingWrite == null) {
+				System.out.println("No more pending writes");
+				reactor.changeOps(key, SelectionKey.OP_READ);
+				break;
+			}
+			
+			doWrite(pendingWrite, key);
+		}
+	}
+
+	protected abstract void doWrite(ByteBuffer pendingWrite, SelectionKey key) throws IOException;
+
+	public void write(ByteBuffer buffer, SelectionKey key) {
+		Queue<ByteBuffer> pendingWrites = this.channelToPendingWrites.get(key.channel());
+		if (pendingWrites == null) {
+			synchronized (this.channelToPendingWrites) {
+				pendingWrites = this.channelToPendingWrites.get(key.channel());
+				if (pendingWrites == null) {
+					pendingWrites = new ConcurrentLinkedQueue<>();
+					this.channelToPendingWrites.put(key.channel(), pendingWrites);
+				}
+			}
+		}
+		pendingWrites.add(buffer);
+		reactor.changeOps(key, SelectionKey.OP_WRITE);
+	}
+}

reactor/src/main/java/com/iluwatar/reactor/App.java

@@ -1,69 +1,32 @@
 package com.iluwatar.reactor;
 
 import java.io.IOException;
-import java.net.InetSocketAddress;
-import java.nio.ByteBuffer;
-import java.nio.channels.DatagramChannel;
-import java.nio.channels.SelectableChannel;
-import java.nio.channels.ServerSocketChannel;
-import java.nio.channels.SocketChannel;
-
-import com.iluwatar.reactor.NioReactor.NioChannelEventHandler;
 
 public class App {
 
 	public static void main(String[] args) {
 		try {
-			NioReactor reactor = new NioReactor();
-
+			NioReactor reactor = new NioReactor(new ThreadPoolDispatcher(2));
+			LoggingHandler loggingHandler = new LoggingHandler();
 			reactor
-				.registerChannel(tcpChannel(6666))
-				.registerChannel(tcpChannel(6667))
+				.registerChannel(tcpChannel(6666, loggingHandler))
+				.registerChannel(tcpChannel(6667, loggingHandler))
+				.registerChannel(udpChannel(6668, loggingHandler))
 			.start();
-
-			reactor.registerHandler(new LoggingServer());
 		} catch (IOException e) {
 			e.printStackTrace();
 		}
 	}
 
-	private static SelectableChannel udpChannel(int port) throws IOException {
-		DatagramChannel channel = DatagramChannel.open();
-		channel.socket().bind(new InetSocketAddress(port));
-		channel.configureBlocking(false);
-		System.out.println("Bound UDP socket at port: " + port);
+	private static AbstractNioChannel tcpChannel(int port, ChannelHandler handler) throws IOException {
+		NioServerSocketChannel channel = new NioServerSocketChannel(port, handler);
+		channel.bind();
 		return channel;
 	}
-
-	private static SelectableChannel tcpChannel(int port) throws IOException {
-		ServerSocketChannel channel = ServerSocketChannel.open();
-		channel.socket().bind(new InetSocketAddress(port));
-		channel.configureBlocking(false);
-		System.out.println("Bound TCP socket at port: " + port);
+	
+	private static AbstractNioChannel udpChannel(int port, ChannelHandler handler) throws IOException {
+		NioDatagramChannel channel = new NioDatagramChannel(port, handler);
+		channel.bind();
 		return channel;
 	}
-
-	static class LoggingServer implements NioChannelEventHandler {
-
-		@Override
-		public void onReadable(SocketChannel channel) {
-			ByteBuffer requestBuffer = ByteBuffer.allocate(1024);
-			try {
-				int byteCount = channel.read(requestBuffer);
-				if (byteCount > 0) {
-					byte[] logRequestContents = new byte[byteCount];
-					byte[] array = requestBuffer.array();
-					System.arraycopy(array, 0, logRequestContents, 0, byteCount);
-					doLogging(new String(logRequestContents));
-				}
-			} catch (IOException e) {
-				e.printStackTrace();
-			}
-		}
-
-		private void doLogging(String log) {
-			// do logging at server side
-			System.out.println(log);
-		}
-	}
 }

reactor/src/main/java/com/iluwatar/reactor/AppClient.java

@@ -1,16 +1,22 @@
 package com.iluwatar.reactor;
 
 import java.io.IOException;
+import java.io.InputStream;
 import java.io.OutputStream;
 import java.io.PrintWriter;
+import java.net.DatagramPacket;
+import java.net.DatagramSocket;
 import java.net.InetAddress;
+import java.net.InetSocketAddress;
 import java.net.Socket;
+import java.net.SocketException;
 
 public class AppClient {
 
 	public static void main(String[] args) {
-		new Thread(new LoggingClient("Client 1", 6666)).start();
-		new Thread(new LoggingClient("Client 2", 6667)).start();
+//		new Thread(new LoggingClient("Client 1", 6666)).start();
+//		new Thread(new LoggingClient("Client 2", 6667)).start();
+		new Thread(new UDPLoggingClient(6668)).start();
 	}
 
 	
@@ -33,7 +39,7 @@ public class AppClient {
 				socket = new Socket(InetAddress.getLocalHost(), serverPort);
 				OutputStream outputStream = socket.getOutputStream();
 				PrintWriter writer = new PrintWriter(outputStream);
-				writeLogs(writer);
+				writeLogs(writer, socket.getInputStream());
 			} catch (IOException e) {
 				e.printStackTrace();
 				throw new RuntimeException(e);
@@ -48,8 +54,8 @@ public class AppClient {
 			}
 		}
 
-		private void writeLogs(PrintWriter writer) {
-			for (int i = 0; i < 10; i++) {
+		private void writeLogs(PrintWriter writer, InputStream inputStream) throws IOException {
+			for (int i = 0; i < 1; i++) {
 				writer.println(clientName + " - Log request: " + i);
 				try {
 					Thread.sleep(100);
@@ -57,6 +63,53 @@ public class AppClient {
 					e.printStackTrace();
 				}
 				writer.flush();
+				byte[] data = new byte[1024];
+				int read = inputStream.read(data, 0, data.length);
+				if (read == 0) {
+					System.out.println("Read zero bytes");
+				} else {
+					System.out.println(new String(data, 0, read));
+				}
+			}
+		}
+	}
+	
+	static class UDPLoggingClient implements Runnable {
+		private int port;
+
+		public UDPLoggingClient(int port) {
+			this.port = port;
+		}
+		
+		@Override
+		public void run() {
+			DatagramSocket socket = null;
+			try {
+				socket = new DatagramSocket();
+				for (int i = 0; i < 1; i++) {
+					String message = "UDP Client" + " - Log request: " + i;
+					try {
+						DatagramPacket packet = new DatagramPacket(message.getBytes(), message.getBytes().length, new InetSocketAddress(InetAddress.getLocalHost(), port));
+						socket.send(packet);
+						
+						byte[] data = new byte[1024];
+						DatagramPacket reply = new DatagramPacket(data, data.length);
+						socket.receive(reply);
+						if (reply.getLength() == 0) {
+							System.out.println("Read zero bytes");
+						} else {
+							System.out.println(new String(reply.getData(), 0, reply.getLength()));
+						}
+					} catch (IOException e) {
+						e.printStackTrace();
+					}
+				}
+			} catch (SocketException e1) {
+				e1.printStackTrace();
+			} finally {
+				if (socket != null) {
+					socket.close();
+				}
 			}
 		}
 	}

reactor/src/main/java/com/iluwatar/reactor/ChannelHandler.java

@@ -0,0 +1,9 @@
+package com.iluwatar.reactor;
+
+import java.nio.ByteBuffer;
+import java.nio.channels.SelectionKey;
+
+public interface ChannelHandler {
+
+	void handleChannelRead(AbstractNioChannel channel, ByteBuffer readBytes, SelectionKey key);
+}

reactor/src/main/java/com/iluwatar/reactor/Dispatcher.java

@@ -0,0 +1,8 @@
+package com.iluwatar.reactor;
+
+import java.nio.ByteBuffer;
+import java.nio.channels.SelectionKey;
+
+public interface Dispatcher {
+	void onChannelReadEvent(AbstractNioChannel channel, ByteBuffer readBytes, SelectionKey key);
+}

reactor/src/main/java/com/iluwatar/reactor/LoggingHandler.java

@@ -0,0 +1,24 @@
+package com.iluwatar.reactor;
+
+import java.nio.ByteBuffer;
+import java.nio.channels.SelectionKey;
+
+public class LoggingHandler implements ChannelHandler {
+
+	@Override
+	public void handleChannelRead(AbstractNioChannel channel, ByteBuffer readBytes, SelectionKey key) {
+		byte[] data = readBytes.array();
+		doLogging(data);
+		sendEchoReply(channel, data, key);
+	}
+
+	private void sendEchoReply(AbstractNioChannel channel, byte[] data, SelectionKey key) {
+		ByteBuffer buffer = ByteBuffer.wrap("Data logged successfully".getBytes());
+		channel.write(buffer, key);
+	}
+
+	private void doLogging(byte[] data) {
+		// assuming UTF-8 :(
+		System.out.println(new String(data));
+	}
+}

reactor/src/main/java/com/iluwatar/reactor/NioDatagramChannel.java

@@ -0,0 +1,47 @@
+package com.iluwatar.reactor;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.nio.ByteBuffer;
+import java.nio.channels.DatagramChannel;
+import java.nio.channels.SelectionKey;
+
+public class NioDatagramChannel extends AbstractNioChannel {
+
+	private int port;
+
+	public NioDatagramChannel(int port, ChannelHandler handler) throws IOException {
+		super(handler, DatagramChannel.open());
+		this.port = port;
+	}
+
+	@Override
+	public int getInterestedOps() {
+		return SelectionKey.OP_READ;
+	}
+
+	@Override
+	public ByteBuffer read(SelectionKey key) throws IOException {
+		ByteBuffer buffer = ByteBuffer.allocate(1024);
+		getChannel().receive(buffer);
+		return buffer;
+	}
+	
+	@Override
+	public DatagramChannel getChannel() {
+		return (DatagramChannel) super.getChannel();
+	}
+	
+	public void bind() throws IOException {
+		getChannel().socket().bind(new InetSocketAddress(InetAddress.getLocalHost(), port));
+		getChannel().configureBlocking(false);
+		System.out.println("Bound UDP socket at port: " + port);
+	}
+
+	@Override
+	protected void doWrite(ByteBuffer pendingWrite, SelectionKey key) throws IOException {
+		pendingWrite.flip();
+		getChannel().write(pendingWrite);
+	}
+}

reactor/src/main/java/com/iluwatar/reactor/NioReactor.java

@@ -1,46 +1,39 @@
 package com.iluwatar.reactor;
 
 import java.io.IOException;
-import java.nio.channels.SelectableChannel;
+import java.nio.ByteBuffer;
 import java.nio.channels.SelectionKey;
 import java.nio.channels.Selector;
 import java.nio.channels.ServerSocketChannel;
 import java.nio.channels.SocketChannel;
-import java.util.List;
+import java.util.Iterator;
+import java.util.Queue;
 import java.util.Set;
-import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.ConcurrentLinkedQueue;
 
 /*
  * Abstractions
  * ---------------
- * 
- * 1 - Dispatcher
  * 2 - Synchronous Event De-multiplexer
- * 3 - Event
- * 4 - Event Handler & concrete event handler (application business logic)
- * 5 - Selector
  */
 public class NioReactor {
 
 	private Selector selector;
-	private Acceptor acceptor;
-	private List<NioChannelEventHandler> eventHandlers = new CopyOnWriteArrayList<>();
+	private Dispatcher dispatcher;
+	private Queue<Command> pendingChanges = new ConcurrentLinkedQueue<>();
 	
-	public NioReactor() throws IOException {
-		this.acceptor = new Acceptor();
+	public NioReactor(Dispatcher dispatcher) throws IOException {
+		this.dispatcher = dispatcher;
 		this.selector = Selector.open();
 	}
 	
-	public NioReactor registerChannel(SelectableChannel channel) throws IOException {
-		SelectionKey key = channel.register(selector, SelectionKey.OP_ACCEPT);
-		key.attach(acceptor);
+	public NioReactor registerChannel(AbstractNioChannel channel) throws IOException {
+		SelectionKey key = channel.getChannel().register(selector, channel.getInterestedOps());
+		key.attach(channel);
+		channel.setReactor(this);
 		return this;
 	}
 	
-	public void registerHandler(NioChannelEventHandler handler) {
-		eventHandlers.add(handler);
-	}
-	
 	public void start() throws IOException {
 		new Thread( new Runnable() {
 			@Override
@@ -52,66 +45,110 @@ public class NioReactor {
 					e.printStackTrace();
 				}
 			}
-		}).start();
+		}, "Reactor Main").start();
 	}
 
 	private void eventLoop() throws IOException {
 		while (true) {
-			selector.select(1000);
+			// honor any pending requests first
+			processPendingChanges();
+			
+			selector.select();
+			
 			Set<SelectionKey> keys = selector.selectedKeys();
-			for (SelectionKey key : keys) {
-				dispatchEvent(key);
+
+			Iterator<SelectionKey> iterator = keys.iterator();
+			
+			while (iterator.hasNext()) {
+				SelectionKey key = iterator.next();
+				if (!key.isValid()) {
+					iterator.remove();
+					continue;
+				}
+				processKey(key);
 			}
 			keys.clear();
 		}
 	}
 	
-	private void dispatchEvent(SelectionKey key) throws IOException {
-		Object handler = key.attachment();
-		if (handler != null) {
-			((EventHandler)handler).handle(key.channel());
+	private void processPendingChanges() {
+		Iterator<Command> iterator = pendingChanges.iterator();
+		while (iterator.hasNext()) {
+			Command command = iterator.next();
+			System.out.println("Processing pending change: " + command);
+			command.execute();
+			iterator.remove();
 		}
 	}
 
-	interface EventHandler {
-		void handle(SelectableChannel channel) throws IOException;
-	}
-
-	private class Acceptor implements EventHandler {
-		
-		public void handle(SelectableChannel channel) throws IOException {
-			// non-blocking accept as acceptor will only be called when accept event is available
-			SocketChannel clientChannel = ((ServerSocketChannel)channel).accept();
-			if (clientChannel != null) {
-				new ChannelHandler(clientChannel).handle(clientChannel);
-			}
-			System.out.println("Connection established with a client");
+	private void processKey(SelectionKey key) throws IOException {
+		if (key.isAcceptable()) {
+			acceptConnection(key);
+		} else if (key.isReadable()) {
+			System.out.println("Key is readable");
+			read(key);
+		} else if (key.isWritable()) {
+			System.out.println("Key is writable");
+			write(key);
 		}
 	}
-	
-	public static interface NioChannelEventHandler {
-		void onReadable(SocketChannel channel);
+
+	private void write(SelectionKey key) throws IOException {
+		AbstractNioChannel channel = (AbstractNioChannel) key.attachment();
+		channel.write(key);
 	}
-	
-	private class ChannelHandler implements EventHandler {
-		
-		private SocketChannel clientChannel;
-		private SelectionKey selectionKey;
 
-		public ChannelHandler(SocketChannel clientChannel) throws IOException {
-			this.clientChannel = clientChannel;
-			clientChannel.configureBlocking(false);
-			selectionKey = clientChannel.register(selector, 0);
-			selectionKey.attach(this);
-			selectionKey.interestOps(SelectionKey.OP_READ);
-			selector.wakeup();
-		}
-
-		public void handle(SelectableChannel channel) throws IOException {
-			// only read events are supported.
-			for (NioChannelEventHandler eventHandler : eventHandlers) {
-				eventHandler.onReadable(clientChannel);
+	private void read(SelectionKey key) {
+		ByteBuffer readBytes;
+		try {
+			readBytes = ((AbstractNioChannel)key.attachment()).read(key);
+			dispatchReadEvent(key, readBytes);
+		} catch (IOException e) {
+			try {
+				key.channel().close();
+			} catch (IOException e1) {
+				e1.printStackTrace();
 			}
 		}
 	}
-}
+
+	private void dispatchReadEvent(SelectionKey key, ByteBuffer readBytes) {
+		dispatcher.onChannelReadEvent((AbstractNioChannel)key.attachment(), readBytes, key);
+	}
+
+	private void acceptConnection(SelectionKey key) throws IOException {
+		ServerSocketChannel serverSocketChannel = (ServerSocketChannel) key.channel();
+		SocketChannel socketChannel = serverSocketChannel.accept();
+		socketChannel.configureBlocking(false);
+		SelectionKey readKey = socketChannel.register(selector, SelectionKey.OP_READ);
+		readKey.attach(key.attachment());
+	}
+
+	interface Command {
+		void execute();
+	}
+	
+	public void changeOps(SelectionKey key, int interestedOps) {
+		pendingChanges.add(new ChangeKeyOpsCommand(key, interestedOps));
+		selector.wakeup();
+	}
+	
+	class ChangeKeyOpsCommand implements Command {
+		private SelectionKey key;
+		private int interestedOps;
+		
+		public ChangeKeyOpsCommand(SelectionKey key, int interestedOps) {
+			this.key = key;
+			this.interestedOps = interestedOps;
+		}
+		
+		public void execute() {
+			key.interestOps(interestedOps);
+		}
+		
+		@Override
+		public String toString() {
+			return "Change of ops to: " + interestedOps;
+		}
+	}
+}

reactor/src/main/java/com/iluwatar/reactor/NioServerSocketChannel.java

@@ -0,0 +1,52 @@
+package com.iluwatar.reactor;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.nio.ByteBuffer;
+import java.nio.channels.SelectionKey;
+import java.nio.channels.ServerSocketChannel;
+import java.nio.channels.SocketChannel;
+
+public class NioServerSocketChannel extends AbstractNioChannel {
+
+	private int port;
+
+	public NioServerSocketChannel(int port, ChannelHandler handler) throws IOException {
+		super(handler, ServerSocketChannel.open());
+		this.port = port;
+	}
+
+	@Override
+	public int getInterestedOps() {
+		return SelectionKey.OP_ACCEPT;
+	}
+
+	@Override
+	public ServerSocketChannel getChannel() {
+		return (ServerSocketChannel) super.getChannel();
+	}
+	
+	@Override
+	public ByteBuffer read(SelectionKey key) throws IOException {
+		SocketChannel socketChannel = (SocketChannel) key.channel();
+		ByteBuffer buffer = ByteBuffer.allocate(1024);
+		int read = socketChannel.read(buffer);
+		if (read == -1) {
+			throw new IOException("Socket closed");
+		}
+		return buffer;
+	}
+
+	public void bind() throws IOException {
+		((ServerSocketChannel)getChannel()).socket().bind(new InetSocketAddress(InetAddress.getLocalHost(), port));
+		((ServerSocketChannel)getChannel()).configureBlocking(false);
+		System.out.println("Bound TCP socket at port: " + port);
+	}
+
+	@Override
+	protected void doWrite(ByteBuffer pendingWrite, SelectionKey key) throws IOException {
+		System.out.println("Writing on channel");
+		((SocketChannel)key.channel()).write(pendingWrite);
+	}
+}

reactor/src/main/java/com/iluwatar/reactor/SameThreadDispatcher.java

@@ -0,0 +1,14 @@
+package com.iluwatar.reactor;
+
+import java.nio.ByteBuffer;
+import java.nio.channels.SelectionKey;
+
+public class SameThreadDispatcher implements Dispatcher {
+
+	@Override
+	public void onChannelReadEvent(AbstractNioChannel channel, ByteBuffer readBytes, SelectionKey key) {
+		if (channel.getHandler() != null) {
+			channel.getHandler().handleChannelRead(channel, readBytes, key);
+		}
+	}
+}

reactor/src/main/java/com/iluwatar/reactor/ThreadPoolDispatcher.java

@@ -0,0 +1,27 @@
+package com.iluwatar.reactor;
+
+import java.nio.ByteBuffer;
+import java.nio.channels.SelectionKey;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+public class ThreadPoolDispatcher extends SameThreadDispatcher {
+
+	private ExecutorService exectorService;
+
+	public ThreadPoolDispatcher(int poolSize) {
+		this.exectorService = Executors.newFixedThreadPool(poolSize);
+	}
+	
+	@Override
+	public void onChannelReadEvent(AbstractNioChannel channel, ByteBuffer readBytes, SelectionKey key) {
+		exectorService.execute(new Runnable() {
+			
+			@Override
+			public void run() {
+				ThreadPoolDispatcher.super.onChannelReadEvent(channel, readBytes, key);
+			}
+		});
+	}
+
+}

reactor/todo.txt

@@ -0,0 +1,4 @@
+* Make UDP channel work (connect is required)
+* Cleanup
+* Document - Javadoc
+* Better design?? Get review of @iluwatar