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Work on #74, updated javadocs, reformatted code to google style guide, added missing final modifiers

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This commit is contained in:
Narendra Pathai 2015-09-12 17:46:24 +05:30
parent aebd69efb4
commit 8d429525dc
12 changed files with 908 additions and 875 deletions
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131
reactor/src/main/java/com/iluwatar/reactor/app/App.java
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@ -10,19 +10,17 @@ import com.iluwatar.reactor.framework.NioServerSocketChannel;
import com.iluwatar.reactor.framework.ThreadPoolDispatcher; import com.iluwatar.reactor.framework.ThreadPoolDispatcher;
/** /**
* This application demonstrates Reactor pattern. The example demonstrated is a Distributed Logging Service * This application demonstrates Reactor pattern. The example demonstrated is a Distributed Logging
* where it listens on multiple TCP or UDP sockets for incoming log requests. * Service where it listens on multiple TCP or UDP sockets for incoming log requests.
* *
* <p> * <p>
* <i>INTENT</i> * <i>INTENT</i> <br/>
* <br/>
* The Reactor design pattern handles service requests that are delivered concurrently to an * The Reactor design pattern handles service requests that are delivered concurrently to an
* application by one or more clients. The application can register specific handlers for processing * application by one or more clients. The application can register specific handlers for processing
* which are called by reactor on specific events. * which are called by reactor on specific events.
* *
* <p> * <p>
* <i>PROBLEM</i> * <i>PROBLEM</i> <br/>
* <br/>
* Server applications in a distributed system must handle multiple clients that send them service * Server applications in a distributed system must handle multiple clients that send them service
* requests. Following forces need to be resolved: * requests. Following forces need to be resolved:
* <ul> * <ul>
@ -33,8 +31,28 @@ import com.iluwatar.reactor.framework.ThreadPoolDispatcher;
* </ul> * </ul>
* *
* <p> * <p>
* The application utilizes single thread to listen for requests on all ports. It does not create * <i>PARTICIPANTS</i> <br/>
* a separate thread for each client, which provides better scalability under load (number of clients * <ul>
* <li>Synchronous Event De-multiplexer</li> {@link NioReactor} plays the role of synchronous event
* de-multiplexer. It waits for events on multiple channels registered to it in an event loop.
*
* <p>
* <li>Initiation Dispatcher</li> {@link NioReactor} plays this role as the application specific
* {@link ChannelHandler}s are registered to the reactor.
*
* <p>
* <li>Handle</li> {@link AbstractNioChannel} acts as a handle that is registered to the reactor.
* When any events occur on a handle, reactor calls the appropriate handler.
*
* <p>
* <li>Event Handler</li> {@link ChannelHandler} acts as an event handler, which is bound to a
* channel and is called back when any event occurs on any of its associated handles. Application
* logic resides in event handlers.
* </ul>
*
* <p>
* The application utilizes single thread to listen for requests on all ports. It does not create a
* separate thread for each client, which provides better scalability under load (number of clients
* increase). * increase).
* *
* <p> * <p>
@ -45,59 +63,60 @@ import com.iluwatar.reactor.framework.ThreadPoolDispatcher;
*/ */
public class App { public class App {
private NioReactor reactor; private NioReactor reactor;
/** /**
* App entry. * App entry.
* @throws IOException *
*/ * @throws IOException
public static void main(String[] args) throws IOException { */
new App().start(); public static void main(String[] args) throws IOException {
} new App().start();
}
/** /**
* Starts the NIO reactor. * Starts the NIO reactor.
* @throws IOException if any channel fails to bind. *
*/ * @throws IOException if any channel fails to bind.
public void start() throws IOException { */
/* public void start() throws IOException {
* The application can customize its event dispatching mechanism. /*
*/ * The application can customize its event dispatching mechanism.
reactor = new NioReactor(new ThreadPoolDispatcher(2)); */
reactor = new NioReactor(new ThreadPoolDispatcher(2));
/* /*
* This represents application specific business logic that dispatcher will call * This represents application specific business logic that dispatcher will call on appropriate
* on appropriate events. These events are read events in our example. * events. These events are read events in our example.
*/ */
LoggingHandler loggingHandler = new LoggingHandler(); LoggingHandler loggingHandler = new LoggingHandler();
/* /*
* Our application binds to multiple channels and uses same logging handler to handle * Our application binds to multiple channels and uses same logging handler to handle incoming
* incoming log requests. * log requests.
*/ */
reactor reactor.registerChannel(tcpChannel(6666, loggingHandler)).registerChannel(tcpChannel(6667, loggingHandler))
.registerChannel(tcpChannel(6666, loggingHandler)) .registerChannel(udpChannel(6668, loggingHandler)).start();
.registerChannel(tcpChannel(6667, loggingHandler)) }
.registerChannel(udpChannel(6668, loggingHandler))
.start();
}
/** /**
* Stops the NIO reactor. This is a blocking call. * Stops the NIO reactor. This is a blocking call.
*/ *
public void stop() { * @throws InterruptedException if interrupted while stopping the reactor.
reactor.stop(); */
} public void stop() throws InterruptedException {
reactor.stop();
}
private static AbstractNioChannel tcpChannel(int port, ChannelHandler handler) throws IOException { private static AbstractNioChannel tcpChannel(int port, ChannelHandler handler) throws IOException {
NioServerSocketChannel channel = new NioServerSocketChannel(port, handler); NioServerSocketChannel channel = new NioServerSocketChannel(port, handler);
channel.bind(); channel.bind();
return channel; return channel;
} }
private static AbstractNioChannel udpChannel(int port, ChannelHandler handler) throws IOException { private static AbstractNioChannel udpChannel(int port, ChannelHandler handler) throws IOException {
NioDatagramChannel channel = new NioDatagramChannel(port, handler); NioDatagramChannel channel = new NioDatagramChannel(port, handler);
channel.bind(); channel.bind();
return channel; return channel;
} }
} }

243
reactor/src/main/java/com/iluwatar/reactor/app/AppClient.java
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@ -21,144 +21,145 @@ import java.util.concurrent.TimeUnit;
* @author npathai * @author npathai
*/ */
public class AppClient { public class AppClient {
private ExecutorService service = Executors.newFixedThreadPool(4); private final ExecutorService service = Executors.newFixedThreadPool(4);
/** /**
* App client entry. * App client entry.
* @throws IOException if any I/O error occurs. *
*/ * @throws IOException if any I/O error occurs.
public static void main(String[] args) throws IOException { */
AppClient appClient = new AppClient(); public static void main(String[] args) throws IOException {
appClient.start(); AppClient appClient = new AppClient();
} appClient.start();
}
/** /**
* Starts the logging clients. * Starts the logging clients.
* @throws IOException if any I/O error occurs. *
*/ * @throws IOException if any I/O error occurs.
public void start() throws IOException { */
service.execute(new TCPLoggingClient("Client 1", 6666)); public void start() throws IOException {
service.execute(new TCPLoggingClient("Client 2", 6667)); service.execute(new TCPLoggingClient("Client 1", 6666));
service.execute(new UDPLoggingClient("Client 3", 6668)); service.execute(new TCPLoggingClient("Client 2", 6667));
service.execute(new UDPLoggingClient("Client 4", 6668)); service.execute(new UDPLoggingClient("Client 3", 6668));
} service.execute(new UDPLoggingClient("Client 4", 6668));
}
/** /**
* Stops logging clients. This is a blocking call. * Stops logging clients. This is a blocking call.
*/ */
public void stop() { public void stop() {
service.shutdown(); service.shutdown();
if (!service.isTerminated()) { if (!service.isTerminated()) {
service.shutdownNow(); service.shutdownNow();
try { try {
service.awaitTermination(1000, TimeUnit.SECONDS); service.awaitTermination(1000, TimeUnit.SECONDS);
} catch (InterruptedException e) { } catch (InterruptedException e) {
e.printStackTrace(); e.printStackTrace();
} }
} }
} }
private static void artificialDelayOf(long millis) { private static void artificialDelayOf(long millis) {
try { try {
Thread.sleep(millis); Thread.sleep(millis);
} catch (InterruptedException e) { } catch (InterruptedException e) {
e.printStackTrace(); e.printStackTrace();
} }
} }
/** /**
* A logging client that sends requests to Reactor on TCP socket. * A logging client that sends requests to Reactor on TCP socket.
*/ */
static class TCPLoggingClient implements Runnable { static class TCPLoggingClient implements Runnable {
private int serverPort; private final int serverPort;
private String clientName; private final String clientName;
/** /**
* Creates a new TCP logging client. * Creates a new TCP logging client.
* *
* @param clientName the name of the client to be sent in logging requests. * @param clientName the name of the client to be sent in logging requests.
* @param port the port on which client will send logging requests. * @param port the port on which client will send logging requests.
*/ */
public TCPLoggingClient(String clientName, int serverPort) { public TCPLoggingClient(String clientName, int serverPort) {
this.clientName = clientName; this.clientName = clientName;
this.serverPort = serverPort; this.serverPort = serverPort;
} }
public void run() { public void run() {
try (Socket socket = new Socket(InetAddress.getLocalHost(), serverPort)) { try (Socket socket = new Socket(InetAddress.getLocalHost(), serverPort)) {
OutputStream outputStream = socket.getOutputStream(); OutputStream outputStream = socket.getOutputStream();
PrintWriter writer = new PrintWriter(outputStream); PrintWriter writer = new PrintWriter(outputStream);
sendLogRequests(writer, socket.getInputStream()); sendLogRequests(writer, socket.getInputStream());
} catch (IOException e) { } catch (IOException e) {
e.printStackTrace(); e.printStackTrace();
throw new RuntimeException(e); throw new RuntimeException(e);
} }
} }
private void sendLogRequests(PrintWriter writer, InputStream inputStream) throws IOException { private void sendLogRequests(PrintWriter writer, InputStream inputStream) throws IOException {
for (int i = 0; i < 4; i++) { for (int i = 0; i < 4; i++) {
writer.println(clientName + " - Log request: " + i); writer.println(clientName + " - Log request: " + i);
writer.flush(); writer.flush();
byte[] data = new byte[1024]; byte[] data = new byte[1024];
int read = inputStream.read(data, 0, data.length); int read = inputStream.read(data, 0, data.length);
if (read == 0) { if (read == 0) {
System.out.println("Read zero bytes"); System.out.println("Read zero bytes");
} else { } else {
System.out.println(new String(data, 0, read)); System.out.println(new String(data, 0, read));
} }
artificialDelayOf(100); artificialDelayOf(100);
} }
} }
} }
/** /**
* A logging client that sends requests to Reactor on UDP socket. * A logging client that sends requests to Reactor on UDP socket.
*/ */
static class UDPLoggingClient implements Runnable { static class UDPLoggingClient implements Runnable {
private String clientName; private final String clientName;
private InetSocketAddress remoteAddress; private final InetSocketAddress remoteAddress;
/** /**
* Creates a new UDP logging client. * Creates a new UDP logging client.
* *
* @param clientName the name of the client to be sent in logging requests. * @param clientName the name of the client to be sent in logging requests.
* @param port the port on which client will send logging requests. * @param port the port on which client will send logging requests.
* @throws UnknownHostException if localhost is unknown * @throws UnknownHostException if localhost is unknown
*/ */
public UDPLoggingClient(String clientName, int port) throws UnknownHostException { public UDPLoggingClient(String clientName, int port) throws UnknownHostException {
this.clientName = clientName; this.clientName = clientName;
this.remoteAddress = new InetSocketAddress(InetAddress.getLocalHost(), port); this.remoteAddress = new InetSocketAddress(InetAddress.getLocalHost(), port);
} }
@Override @Override
public void run() { public void run() {
try (DatagramSocket socket = new DatagramSocket()) { try (DatagramSocket socket = new DatagramSocket()) {
for (int i = 0; i < 4; i++) { for (int i = 0; i < 4; i++) {
String message = clientName + " - Log request: " + i; String message = clientName + " - Log request: " + i;
DatagramPacket request = new DatagramPacket(message.getBytes(), DatagramPacket request = new DatagramPacket(message.getBytes(), message.getBytes().length, remoteAddress);
message.getBytes().length, remoteAddress);
socket.send(request); socket.send(request);
byte[] data = new byte[1024]; byte[] data = new byte[1024];
DatagramPacket reply = new DatagramPacket(data, data.length); DatagramPacket reply = new DatagramPacket(data, data.length);
socket.receive(reply); socket.receive(reply);
if (reply.getLength() == 0) { if (reply.getLength() == 0) {
System.out.println("Read zero bytes"); System.out.println("Read zero bytes");
} else { } else {
System.out.println(new String(reply.getData(), 0, reply.getLength())); System.out.println(new String(reply.getData(), 0, reply.getLength()));
} }
artificialDelayOf(100); artificialDelayOf(100);
} }
} catch (IOException e1) { } catch (IOException e1) {
e1.printStackTrace(); e1.printStackTrace();
} }
} }
} }
} }

79
reactor/src/main/java/com/iluwatar/reactor/app/LoggingHandler.java
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@ -8,53 +8,54 @@ import com.iluwatar.reactor.framework.ChannelHandler;
import com.iluwatar.reactor.framework.NioDatagramChannel.DatagramPacket; import com.iluwatar.reactor.framework.NioDatagramChannel.DatagramPacket;
/** /**
* Logging server application logic. It logs the incoming requests on standard console and returns * Logging server application logic. It logs the incoming requests on standard console and returns a
* a canned acknowledgement back to the remote peer. * canned acknowledgement back to the remote peer.
* *
* @author npathai * @author npathai
*/ */
public class LoggingHandler implements ChannelHandler { public class LoggingHandler implements ChannelHandler {
private static final byte[] ACK = "Data logged successfully".getBytes(); private static final byte[] ACK = "Data logged successfully".getBytes();
/** /**
* Decodes the received data and logs it on standard console. * Decodes the received data and logs it on standard console.
*/ */
@Override @Override
public void handleChannelRead(AbstractNioChannel channel, Object readObject, SelectionKey key) { public void handleChannelRead(AbstractNioChannel channel, Object readObject, SelectionKey key) {
/* /*
* As this handler is attached with both TCP and UDP channels we need to check whether * As this handler is attached with both TCP and UDP channels we need to check whether the data
* the data received is a ByteBuffer (from TCP channel) or a DatagramPacket (from UDP channel). * received is a ByteBuffer (from TCP channel) or a DatagramPacket (from UDP channel).
*/ */
if (readObject instanceof ByteBuffer) { if (readObject instanceof ByteBuffer) {
doLogging(((ByteBuffer)readObject)); doLogging(((ByteBuffer) readObject));
sendReply(channel, key); sendReply(channel, key);
} else if (readObject instanceof DatagramPacket) { } else if (readObject instanceof DatagramPacket) {
DatagramPacket datagram = (DatagramPacket)readObject; DatagramPacket datagram = (DatagramPacket) readObject;
doLogging(datagram.getData()); doLogging(datagram.getData());
sendReply(channel, datagram, key); sendReply(channel, datagram, key);
} else { } else {
throw new IllegalStateException("Unknown data received"); throw new IllegalStateException("Unknown data received");
} }
} }
private void sendReply(AbstractNioChannel channel, DatagramPacket incomingPacket, SelectionKey key) { private void sendReply(AbstractNioChannel channel, DatagramPacket incomingPacket, SelectionKey key) {
/* /*
* Create a reply acknowledgement datagram packet setting the receiver to the sender of incoming message. * Create a reply acknowledgement datagram packet setting the receiver to the sender of incoming
*/ * message.
DatagramPacket replyPacket = new DatagramPacket(ByteBuffer.wrap(ACK)); */
replyPacket.setReceiver(incomingPacket.getSender()); DatagramPacket replyPacket = new DatagramPacket(ByteBuffer.wrap(ACK));
replyPacket.setReceiver(incomingPacket.getSender());
channel.write(replyPacket, key); channel.write(replyPacket, key);
} }
private void sendReply(AbstractNioChannel channel, SelectionKey key) { private void sendReply(AbstractNioChannel channel, SelectionKey key) {
ByteBuffer buffer = ByteBuffer.wrap(ACK); ByteBuffer buffer = ByteBuffer.wrap(ACK);
channel.write(buffer, key); channel.write(buffer, key);
} }
private void doLogging(ByteBuffer data) { private void doLogging(ByteBuffer data) {
// assuming UTF-8 :( // assuming UTF-8 :(
System.out.println(new String(data.array(), 0, data.limit())); System.out.println(new String(data.array(), 0, data.limit()));
} }
} }

242
reactor/src/main/java/com/iluwatar/reactor/framework/AbstractNioChannel.java
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@ -10,143 +10,145 @@ import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentLinkedQueue; import java.util.concurrent.ConcurrentLinkedQueue;
/** /**
* This represents the <i>Handle</i> of Reactor pattern. These are resources managed by OS * This represents the <i>Handle</i> of Reactor pattern. These are resources managed by OS which can
* which can be submitted to {@link NioReactor}. * be submitted to {@link NioReactor}.
* *
* <p> * <p>
* This class serves has the responsibility of reading the data when a read event occurs and * This class serves has the responsibility of reading the data when a read event occurs and writing
* writing the data back when the channel is writable. It leaves the reading and writing of * the data back when the channel is writable. It leaves the reading and writing of data on the
* data on the concrete implementation. It provides a block writing mechanism wherein when * concrete implementation. It provides a block writing mechanism wherein when any
* any {@link ChannelHandler} wants to write data back, it queues the data in pending write queue * {@link ChannelHandler} wants to write data back, it queues the data in pending write queue and
* and clears it in block manner. This provides better throughput. * clears it in block manner. This provides better throughput.
* *
* @author npathai * @author npathai
* *
*/ */
public abstract class AbstractNioChannel { public abstract class AbstractNioChannel {
private SelectableChannel channel; private final SelectableChannel channel;
private ChannelHandler handler; private final ChannelHandler handler;
private Map<SelectableChannel, Queue<Object>> channelToPendingWrites = new ConcurrentHashMap<>(); private final Map<SelectableChannel, Queue<Object>> channelToPendingWrites = new ConcurrentHashMap<>();
private NioReactor reactor; private NioReactor reactor;
/** /**
* Creates a new channel. * Creates a new channel.
* @param handler which will handle events occurring on this channel. *
* @param channel a NIO channel to be wrapped. * @param handler which will handle events occurring on this channel.
*/ * @param channel a NIO channel to be wrapped.
public AbstractNioChannel(ChannelHandler handler, SelectableChannel channel) { */
this.handler = handler; public AbstractNioChannel(ChannelHandler handler, SelectableChannel channel) {
this.channel = channel; this.handler = handler;
} this.channel = channel;
}
/** /**
* Injects the reactor in this channel. * Injects the reactor in this channel.
*/ */
void setReactor(NioReactor reactor) { void setReactor(NioReactor reactor) {
this.reactor = reactor; this.reactor = reactor;
} }
/** /**
* @return the wrapped NIO channel. * @return the wrapped NIO channel.
*/ */
public SelectableChannel getChannel() { public SelectableChannel getChannel() {
return channel; return channel;
} }
/** /**
* The operation in which the channel is interested, this operation is provided to {@link Selector}. * The operation in which the channel is interested, this operation is provided to
* * {@link Selector}.
* @return interested operation. *
* @see SelectionKey * @return interested operation.
*/ * @see SelectionKey
public abstract int getInterestedOps(); */
public abstract int getInterestedOps();
/** /**
* Binds the channel on provided port. * Binds the channel on provided port.
* *
* @throws IOException if any I/O error occurs. * @throws IOException if any I/O error occurs.
*/ */
public abstract void bind() throws IOException; public abstract void bind() throws IOException;
/** /**
* Reads the data using the key and returns the read data. The underlying channel should be fetched using * Reads the data using the key and returns the read data. The underlying channel should be
* {@link SelectionKey#channel()}. * fetched using {@link SelectionKey#channel()}.
* *
* @param key the key on which read event occurred. * @param key the key on which read event occurred.
* @return data read. * @return data read.
* @throws IOException if any I/O error occurs. * @throws IOException if any I/O error occurs.
*/ */
public abstract Object read(SelectionKey key) throws IOException; public abstract Object read(SelectionKey key) throws IOException;
/** /**
* @return the handler associated with this channel. * @return the handler associated with this channel.
*/ */
public ChannelHandler getHandler() { public ChannelHandler getHandler() {
return handler; return handler;
} }
/* /*
* Called from the context of reactor thread when the key becomes writable. * Called from the context of reactor thread when the key becomes writable. The channel writes the
* The channel writes the whole pending block of data at once. * whole pending block of data at once.
*/ */
void flush(SelectionKey key) throws IOException { void flush(SelectionKey key) throws IOException {
Queue<Object> pendingWrites = channelToPendingWrites.get(key.channel()); Queue<Object> pendingWrites = channelToPendingWrites.get(key.channel());
while (true) { while (true) {
Object pendingWrite = pendingWrites.poll(); Object pendingWrite = pendingWrites.poll();
if (pendingWrite == null) { if (pendingWrite == null) {
// We don't have anything more to write so channel is interested in reading more data // We don't have anything more to write so channel is interested in reading more data
reactor.changeOps(key, SelectionKey.OP_READ); reactor.changeOps(key, SelectionKey.OP_READ);
break; break;
} }
// ask the concrete channel to make sense of data and write it to java channel // ask the concrete channel to make sense of data and write it to java channel
doWrite(pendingWrite, key); doWrite(pendingWrite, key);
} }
} }
/** /**
* Writes the data to the channel. * Writes the data to the channel.
* *
* @param pendingWrite the data to be written on channel. * @param pendingWrite the data to be written on channel.
* @param key the key which is writable. * @param key the key which is writable.
* @throws IOException if any I/O error occurs. * @throws IOException if any I/O error occurs.
*/ */
protected abstract void doWrite(Object pendingWrite, SelectionKey key) throws IOException; protected abstract void doWrite(Object pendingWrite, SelectionKey key) throws IOException;
/** /**
* Queues the data for writing. The data is not guaranteed to be written on underlying channel * Queues the data for writing. The data is not guaranteed to be written on underlying channel
* when this method returns. It will be written when the channel is flushed. * when this method returns. It will be written when the channel is flushed.
* *
* <p> * <p>
* This method is used by the {@link ChannelHandler} to send reply back to the client. * This method is used by the {@link ChannelHandler} to send reply back to the client. <br/>
* <br/> * Example:
* Example: *
* <pre> * <pre>
* <code> * <code>
* {@literal @}Override * {@literal @}Override
* public void handleChannelRead(AbstractNioChannel channel, Object readObject, SelectionKey key) { * public void handleChannelRead(AbstractNioChannel channel, Object readObject, SelectionKey key) {
* byte[] data = ((ByteBuffer)readObject).array(); * byte[] data = ((ByteBuffer)readObject).array();
* ByteBuffer buffer = ByteBuffer.wrap("Server reply".getBytes()); * ByteBuffer buffer = ByteBuffer.wrap("Server reply".getBytes());
* channel.write(buffer, key); * channel.write(buffer, key);
* } * }
* </code> * </code>
* *
* @param data the data to be written on underlying channel. * @param data the data to be written on underlying channel.
* @param key the key which is writable. * @param key the key which is writable.
*/ */
public void write(Object data, SelectionKey key) { public void write(Object data, SelectionKey key) {
Queue<Object> pendingWrites = this.channelToPendingWrites.get(key.channel()); Queue<Object> pendingWrites = this.channelToPendingWrites.get(key.channel());
if (pendingWrites == null) { if (pendingWrites == null) {
synchronized (this.channelToPendingWrites) { synchronized (this.channelToPendingWrites) {
pendingWrites = this.channelToPendingWrites.get(key.channel()); pendingWrites = this.channelToPendingWrites.get(key.channel());
if (pendingWrites == null) { if (pendingWrites == null) {
pendingWrites = new ConcurrentLinkedQueue<>(); pendingWrites = new ConcurrentLinkedQueue<>();
this.channelToPendingWrites.put(key.channel(), pendingWrites); this.channelToPendingWrites.put(key.channel(), pendingWrites);
} }
} }
} }
pendingWrites.add(data); pendingWrites.add(data);
reactor.changeOps(key, SelectionKey.OP_WRITE); reactor.changeOps(key, SelectionKey.OP_WRITE);
} }
} }

20
reactor/src/main/java/com/iluwatar/reactor/framework/ChannelHandler.java
View File

@ -7,19 +7,19 @@ import java.nio.channels.SelectionKey;
* to it by the {@link Dispatcher}. This is where the application logic resides. * to it by the {@link Dispatcher}. This is where the application logic resides.
* *
* <p> * <p>
* A {@link ChannelHandler} can be associated with one or many {@link AbstractNioChannel}s, and whenever * A {@link ChannelHandler} can be associated with one or many {@link AbstractNioChannel}s, and
* an event occurs on any of the associated channels, the handler is notified of the event. * whenever an event occurs on any of the associated channels, the handler is notified of the event.
* *
* @author npathai * @author npathai
*/ */
public interface ChannelHandler { public interface ChannelHandler {
/** /**
* Called when the {@code channel} receives some data from remote peer. * Called when the {@code channel} receives some data from remote peer.
* *
* @param channel the channel from which the data was received. * @param channel the channel from which the data was received.
* @param readObject the data read. * @param readObject the data read.
* @param key the key on which read event occurred. * @param key the key on which read event occurred.
*/ */
void handleChannelRead(AbstractNioChannel channel, Object readObject, SelectionKey key); void handleChannelRead(AbstractNioChannel channel, Object readObject, SelectionKey key);
} }

50
reactor/src/main/java/com/iluwatar/reactor/framework/Dispatcher.java
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@ -4,15 +4,15 @@ import java.nio.channels.SelectionKey;
/** /**
* Represents the event dispatching strategy. When {@link NioReactor} senses any event on the * Represents the event dispatching strategy. When {@link NioReactor} senses any event on the
* registered {@link AbstractNioChannel}s then it de-multiplexes the event type, read or write * registered {@link AbstractNioChannel}s then it de-multiplexes the event type, read or write or
* or connect, and then calls the {@link Dispatcher} to dispatch the read events. This decouples the I/O * connect, and then calls the {@link Dispatcher} to dispatch the read events. This decouples the
* processing from application specific processing. * I/O processing from application specific processing. <br/>
* <br/> * Dispatcher should call the {@link ChannelHandler} associated with the channel on which event
* Dispatcher should call the {@link ChannelHandler} associated with the channel on which event occurred. * occurred.
* *
* <p> * <p>
* The application can customize the way in which event is dispatched such as using the reactor thread to * The application can customize the way in which event is dispatched such as using the reactor
* dispatch event to channels or use a worker pool to do the non I/O processing. * thread to dispatch event to channels or use a worker pool to do the non I/O processing.
* *
* @see SameThreadDispatcher * @see SameThreadDispatcher
* @see ThreadPoolDispatcher * @see ThreadPoolDispatcher
@ -20,22 +20,24 @@ import java.nio.channels.SelectionKey;
* @author npathai * @author npathai
*/ */
public interface Dispatcher { public interface Dispatcher {
/** /**
* This hook method is called when read event occurs on particular channel. The data read * This hook method is called when read event occurs on particular channel. The data read is
* is provided in <code>readObject</code>. The implementation should dispatch this read event * provided in <code>readObject</code>. The implementation should dispatch this read event to the
* to the associated {@link ChannelHandler} of <code>channel</code>. * associated {@link ChannelHandler} of <code>channel</code>.
* *
* <p> * <p>
* The type of <code>readObject</code> depends on the channel on which data was received. * The type of <code>readObject</code> depends on the channel on which data was received.
* *
* @param channel on which read event occurred * @param channel on which read event occurred
* @param readObject object read by channel * @param readObject object read by channel
* @param key on which event occurred * @param key on which event occurred
*/ */
void onChannelReadEvent(AbstractNioChannel channel, Object readObject, SelectionKey key); void onChannelReadEvent(AbstractNioChannel channel, Object readObject, SelectionKey key);
/** /**
* Stops dispatching events and cleans up any acquired resources such as threads. * Stops dispatching events and cleans up any acquired resources such as threads.
*/ *
void stop(); * @throws InterruptedException if interrupted while stopping dispatcher.
*/
void stop() throws InterruptedException;
} }

250
reactor/src/main/java/com/iluwatar/reactor/framework/NioDatagramChannel.java
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@ -15,143 +15,147 @@ import java.nio.channels.SelectionKey;
*/ */
public class NioDatagramChannel extends AbstractNioChannel { public class NioDatagramChannel extends AbstractNioChannel {
private int port; private final int port;
/** /**
* Creates a {@link DatagramChannel} which will bind at provided port and use <code>handler</code> to handle * Creates a {@link DatagramChannel} which will bind at provided port and use <code>handler</code>
* incoming events on this channel. * to handle incoming events on this channel.
* <p> * <p>
* Note the constructor does not bind the socket, {@link #bind()} method should be called for binding * Note the constructor does not bind the socket, {@link #bind()} method should be called for
* the socket. * binding the socket.
* *
* @param port the port to be bound to listen for incoming datagram requests. * @param port the port to be bound to listen for incoming datagram requests.
* @param handler the handler to be used for handling incoming requests on this channel. * @param handler the handler to be used for handling incoming requests on this channel.
* @throws IOException if any I/O error occurs. * @throws IOException if any I/O error occurs.
*/ */
public NioDatagramChannel(int port, ChannelHandler handler) throws IOException { public NioDatagramChannel(int port, ChannelHandler handler) throws IOException {
super(handler, DatagramChannel.open()); super(handler, DatagramChannel.open());
this.port = port; this.port = port;
} }
@Override @Override
public int getInterestedOps() { public int getInterestedOps() {
/* there is no need to accept connections in UDP, so the channel shows interest in /*
* reading data. * there is no need to accept connections in UDP, so the channel shows interest in reading data.
*/ */
return SelectionKey.OP_READ; return SelectionKey.OP_READ;
} }
/** /**
* Reads and returns a {@link DatagramPacket} from the underlying channel. * Reads and returns a {@link DatagramPacket} from the underlying channel.
* @return the datagram packet read having the sender address. *
*/ * @return the datagram packet read having the sender address.
@Override */
public DatagramPacket read(SelectionKey key) throws IOException { @Override
ByteBuffer buffer = ByteBuffer.allocate(1024); public DatagramPacket read(SelectionKey key) throws IOException {
SocketAddress sender = ((DatagramChannel)key.channel()).receive(buffer); ByteBuffer buffer = ByteBuffer.allocate(1024);
SocketAddress sender = ((DatagramChannel) key.channel()).receive(buffer);
/* /*
* It is required to create a DatagramPacket because we need to preserve which * It is required to create a DatagramPacket because we need to preserve which socket address
* socket address acts as destination for sending reply packets. * acts as destination for sending reply packets.
*/ */
buffer.flip(); buffer.flip();
DatagramPacket packet = new DatagramPacket(buffer); DatagramPacket packet = new DatagramPacket(buffer);
packet.setSender(sender); packet.setSender(sender);
return packet; return packet;
} }
/** /**
* @return the underlying datagram channel. * @return the underlying datagram channel.
*/ */
@Override @Override
public DatagramChannel getChannel() { public DatagramChannel getChannel() {
return (DatagramChannel) super.getChannel(); return (DatagramChannel) super.getChannel();
} }
/** /**
* Binds UDP socket on the provided <code>port</code>. * Binds UDP socket on the provided <code>port</code>.
* *
* @throws IOException if any I/O error occurs. * @throws IOException if any I/O error occurs.
*/ */
@Override @Override
public void bind() throws IOException { public void bind() throws IOException {
getChannel().socket().bind(new InetSocketAddress(InetAddress.getLocalHost(), port)); getChannel().socket().bind(new InetSocketAddress(InetAddress.getLocalHost(), port));
getChannel().configureBlocking(false); getChannel().configureBlocking(false);
System.out.println("Bound UDP socket at port: " + port); System.out.println("Bound UDP socket at port: " + port);
} }
/** /**
* Writes the pending {@link DatagramPacket} to the underlying channel sending data to * Writes the pending {@link DatagramPacket} to the underlying channel sending data to the
* the intended receiver of the packet. * intended receiver of the packet.
*/ */
@Override @Override
protected void doWrite(Object pendingWrite, SelectionKey key) throws IOException { protected void doWrite(Object pendingWrite, SelectionKey key) throws IOException {
DatagramPacket pendingPacket = (DatagramPacket) pendingWrite; DatagramPacket pendingPacket = (DatagramPacket) pendingWrite;
getChannel().send(pendingPacket.getData(), pendingPacket.getReceiver()); getChannel().send(pendingPacket.getData(), pendingPacket.getReceiver());
} }
/** /**
* Writes the outgoing {@link DatagramPacket} to the channel. The intended receiver of the * Writes the outgoing {@link DatagramPacket} to the channel. The intended receiver of the
* datagram packet must be set in the <code>data</code> using {@link DatagramPacket#setReceiver(SocketAddress)}. * datagram packet must be set in the <code>data</code> using
*/ * {@link DatagramPacket#setReceiver(SocketAddress)}.
@Override */
public void write(Object data, SelectionKey key) { @Override
super.write(data, key); public void write(Object data, SelectionKey key) {
} super.write(data, key);
}
/** /**
* Container of data used for {@link NioDatagramChannel} to communicate with remote peer. * Container of data used for {@link NioDatagramChannel} to communicate with remote peer.
*/ */
public static class DatagramPacket { public static class DatagramPacket {
private SocketAddress sender; private SocketAddress sender;
private ByteBuffer data; private ByteBuffer data;
private SocketAddress receiver; private SocketAddress receiver;
/** /**
* Creates a container with underlying data. * Creates a container with underlying data.
* *
* @param data the underlying message to be written on channel. * @param data the underlying message to be written on channel.
*/ */
public DatagramPacket(ByteBuffer data) { public DatagramPacket(ByteBuffer data) {
this.data = data; this.data = data;
} }
/** /**
* @return the sender address. * @return the sender address.
*/ */
public SocketAddress getSender() { public SocketAddress getSender() {
return sender; return sender;
} }
/** /**
* Sets the sender address of this packet. * Sets the sender address of this packet.
* @param sender the sender address. *
*/ * @param sender the sender address.
public void setSender(SocketAddress sender) { */
this.sender = sender; public void setSender(SocketAddress sender) {
} this.sender = sender;
}
/** /**
* @return the receiver address. * @return the receiver address.
*/ */
public SocketAddress getReceiver() { public SocketAddress getReceiver() {
return receiver; return receiver;
} }
/** /**
* Sets the intended receiver address. This must be set when writing to the channel. * Sets the intended receiver address. This must be set when writing to the channel.
* @param receiver the receiver address. *
*/ * @param receiver the receiver address.
public void setReceiver(SocketAddress receiver) { */
this.receiver = receiver; public void setReceiver(SocketAddress receiver) {
} this.receiver = receiver;
}
/** /**
* @return the underlying message that will be written on channel. * @return the underlying message that will be written on channel.
*/ */
public ByteBuffer getData() { public ByteBuffer getData() {
return data; return data;
} }
} }
} }

373
reactor/src/main/java/com/iluwatar/reactor/framework/NioReactor.java
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@ -12,228 +12,225 @@ import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.ExecutorService; import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors; import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit; import java.util.concurrent.TimeUnit;
/** /**
* This class acts as Synchronous Event De-multiplexer and Initiation Dispatcher of Reactor pattern. * This class acts as Synchronous Event De-multiplexer and Initiation Dispatcher of Reactor pattern.
* Multiple handles i.e. {@link AbstractNioChannel}s can be registered to the reactor and it blocks * Multiple handles i.e. {@link AbstractNioChannel}s can be registered to the reactor and it blocks
* for events from all these handles. Whenever an event occurs on any of the registered handles, * for events from all these handles. Whenever an event occurs on any of the registered handles, it
* it synchronously de-multiplexes the event which can be any of read, write or accept, and * synchronously de-multiplexes the event which can be any of read, write or accept, and dispatches
* dispatches the event to the appropriate {@link ChannelHandler} using the {@link Dispatcher}. * the event to the appropriate {@link ChannelHandler} using the {@link Dispatcher}.
* *
* <p> * <p>
* Implementation: * Implementation: A NIO reactor runs in its own thread when it is started using {@link #start()}
* A NIO reactor runs in its own thread when it is started using {@link #start()} method. * method. {@link NioReactor} uses {@link Selector} for realizing Synchronous Event De-multiplexing.
* {@link NioReactor} uses {@link Selector} for realizing Synchronous Event De-multiplexing.
* *
* <p> * <p>
* NOTE: This is one of the ways to implement NIO reactor and it does not take care of all possible edge cases * NOTE: This is one of the ways to implement NIO reactor and it does not take care of all possible
* which are required in a real application. This implementation is meant to demonstrate the fundamental * edge cases which are required in a real application. This implementation is meant to demonstrate
* concepts that lie behind Reactor pattern. * the fundamental concepts that lie behind Reactor pattern.
* *
* @author npathai * @author npathai
* *
*/ */
public class NioReactor { public class NioReactor {
private Selector selector; private final Selector selector;
private Dispatcher dispatcher; private final Dispatcher dispatcher;
/** /**
* All the work of altering the SelectionKey operations and Selector operations are performed in * All the work of altering the SelectionKey operations and Selector operations are performed in
* the context of main event loop of reactor. So when any channel needs to change its readability * the context of main event loop of reactor. So when any channel needs to change its readability
* or writability, a new command is added in the command queue and then the event loop picks up * or writability, a new command is added in the command queue and then the event loop picks up
* the command and executes it in next iteration. * the command and executes it in next iteration.
*/ */
private Queue<Runnable> pendingCommands = new ConcurrentLinkedQueue<>(); private final Queue<Runnable> pendingCommands = new ConcurrentLinkedQueue<>();
private ExecutorService reactorMain = Executors.newSingleThreadExecutor(); private final ExecutorService reactorMain = Executors.newSingleThreadExecutor();
/** /**
* Creates a reactor which will use provided {@code dispatcher} to dispatch events. * Creates a reactor which will use provided {@code dispatcher} to dispatch events. The
* The application can provide various implementations of dispatcher which suits its * application can provide various implementations of dispatcher which suits its needs.
* needs. *
* * @param dispatcher a non-null dispatcher used to dispatch events on registered channels.
* @param dispatcher a non-null dispatcher used to dispatch events on registered channels. * @throws IOException if any I/O error occurs.
* @throws IOException if any I/O error occurs. */
*/ public NioReactor(Dispatcher dispatcher) throws IOException {
public NioReactor(Dispatcher dispatcher) throws IOException { this.dispatcher = dispatcher;
this.dispatcher = dispatcher; this.selector = Selector.open();
this.selector = Selector.open(); }
}
/** /**
* Starts the reactor event loop in a new thread. * Starts the reactor event loop in a new thread.
* *
* @throws IOException if any I/O error occurs. * @throws IOException if any I/O error occurs.
*/ */
public void start() throws IOException { public void start() throws IOException {
reactorMain.execute(() -> { reactorMain.execute(() -> {
try { try {
System.out.println("Reactor started, waiting for events..."); System.out.println("Reactor started, waiting for events...");
eventLoop(); eventLoop();
} catch (IOException e) { } catch (IOException e) {
e.printStackTrace(); e.printStackTrace();
} }
}); });
} }
/** /**
* Stops the reactor and related resources such as dispatcher. * Stops the reactor and related resources such as dispatcher.
*/ *
public void stop() { * @throws InterruptedException if interrupted while stopping the reactor.
reactorMain.shutdownNow(); */
selector.wakeup(); public void stop() throws InterruptedException {
try { reactorMain.shutdownNow();
reactorMain.awaitTermination(4, TimeUnit.SECONDS); selector.wakeup();
} catch (InterruptedException e) { reactorMain.awaitTermination(4, TimeUnit.SECONDS);
e.printStackTrace(); dispatcher.stop();
} }
dispatcher.stop();
}
/** /**
* Registers a new channel (handle) with this reactor. Reactor will start waiting for events on this channel * Registers a new channel (handle) with this reactor. Reactor will start waiting for events on
* and notify of any events. While registering the channel the reactor uses {@link AbstractNioChannel#getInterestedOps()} * this channel and notify of any events. While registering the channel the reactor uses
* to know about the interested operation of this channel. * {@link AbstractNioChannel#getInterestedOps()} to know about the interested operation of this
* * channel.
* @param channel a new channel on which reactor will wait for events. The channel must be bound *
* prior to being registered. * @param channel a new channel on which reactor will wait for events. The channel must be bound
* @return this * prior to being registered.
* @throws IOException if any I/O error occurs. * @return this
*/ * @throws IOException if any I/O error occurs.
public NioReactor registerChannel(AbstractNioChannel channel) throws IOException { */
SelectionKey key = channel.getChannel().register(selector, channel.getInterestedOps()); public NioReactor registerChannel(AbstractNioChannel channel) throws IOException {
key.attach(channel); SelectionKey key = channel.getChannel().register(selector, channel.getInterestedOps());
channel.setReactor(this); key.attach(channel);
return this; channel.setReactor(this);
} return this;
}
private void eventLoop() throws IOException { private void eventLoop() throws IOException {
while (true) { while (true) {
// honor interrupt request // honor interrupt request
if (Thread.interrupted()) { if (Thread.interrupted()) {
break; break;
} }
// honor any pending commands first // honor any pending commands first
processPendingCommands(); processPendingCommands();
/* /*
* Synchronous event de-multiplexing happens here, this is blocking call which * Synchronous event de-multiplexing happens here, this is blocking call which returns when it
* returns when it is possible to initiate non-blocking operation on any of the * is possible to initiate non-blocking operation on any of the registered channels.
* registered channels. */
*/ selector.select();
selector.select();
/* /*
* Represents the events that have occurred on registered handles. * Represents the events that have occurred on registered handles.
*/ */
Set<SelectionKey> keys = selector.selectedKeys(); Set<SelectionKey> keys = selector.selectedKeys();
Iterator<SelectionKey> iterator = keys.iterator(); Iterator<SelectionKey> iterator = keys.iterator();
while (iterator.hasNext()) { while (iterator.hasNext()) {
SelectionKey key = iterator.next(); SelectionKey key = iterator.next();
if (!key.isValid()) { if (!key.isValid()) {
iterator.remove(); iterator.remove();
continue; continue;
} }
processKey(key); processKey(key);
} }
keys.clear(); keys.clear();
} }
} }
private void processPendingCommands() { private void processPendingCommands() {
Iterator<Runnable> iterator = pendingCommands.iterator(); Iterator<Runnable> iterator = pendingCommands.iterator();
while (iterator.hasNext()) { while (iterator.hasNext()) {
Runnable command = iterator.next(); Runnable command = iterator.next();
command.run(); command.run();
iterator.remove(); iterator.remove();
} }
} }
/* /*
* Initiation dispatcher logic, it checks the type of event and notifier application * Initiation dispatcher logic, it checks the type of event and notifier application specific
* specific event handler to handle the event. * event handler to handle the event.
*/ */
private void processKey(SelectionKey key) throws IOException { private void processKey(SelectionKey key) throws IOException {
if (key.isAcceptable()) { if (key.isAcceptable()) {
onChannelAcceptable(key); onChannelAcceptable(key);
} else if (key.isReadable()) { } else if (key.isReadable()) {
onChannelReadable(key); onChannelReadable(key);
} else if (key.isWritable()) { } else if (key.isWritable()) {
onChannelWritable(key); onChannelWritable(key);
} }
} }
private void onChannelWritable(SelectionKey key) throws IOException { private void onChannelWritable(SelectionKey key) throws IOException {
AbstractNioChannel channel = (AbstractNioChannel) key.attachment(); AbstractNioChannel channel = (AbstractNioChannel) key.attachment();
channel.flush(key); channel.flush(key);
} }
private void onChannelReadable(SelectionKey key) { private void onChannelReadable(SelectionKey key) {
try { try {
// reads the incoming data in context of reactor main loop. Can this be improved? // reads the incoming data in context of reactor main loop. Can this be improved?
Object readObject = ((AbstractNioChannel)key.attachment()).read(key); Object readObject = ((AbstractNioChannel) key.attachment()).read(key);
dispatchReadEvent(key, readObject); dispatchReadEvent(key, readObject);
} catch (IOException e) { } catch (IOException e) {
try { try {
key.channel().close(); key.channel().close();
} catch (IOException e1) { } catch (IOException e1) {
e1.printStackTrace(); e1.printStackTrace();
} }
} }
} }
/* /*
* Uses the application provided dispatcher to dispatch events to application handler. * Uses the application provided dispatcher to dispatch events to application handler.
*/ */
private void dispatchReadEvent(SelectionKey key, Object readObject) { private void dispatchReadEvent(SelectionKey key, Object readObject) {
dispatcher.onChannelReadEvent((AbstractNioChannel)key.attachment(), readObject, key); dispatcher.onChannelReadEvent((AbstractNioChannel) key.attachment(), readObject, key);
} }
private void onChannelAcceptable(SelectionKey key) throws IOException { private void onChannelAcceptable(SelectionKey key) throws IOException {
ServerSocketChannel serverSocketChannel = (ServerSocketChannel) key.channel(); ServerSocketChannel serverSocketChannel = (ServerSocketChannel) key.channel();
SocketChannel socketChannel = serverSocketChannel.accept(); SocketChannel socketChannel = serverSocketChannel.accept();
socketChannel.configureBlocking(false); socketChannel.configureBlocking(false);
SelectionKey readKey = socketChannel.register(selector, SelectionKey.OP_READ); SelectionKey readKey = socketChannel.register(selector, SelectionKey.OP_READ);
readKey.attach(key.attachment()); readKey.attach(key.attachment());
} }
/** /**
* Queues the change of operations request of a channel, which will change the interested * Queues the change of operations request of a channel, which will change the interested
* operations of the channel sometime in future. * operations of the channel sometime in future.
* <p> * <p>
* This is a non-blocking method and does not guarantee that the operations have changed when * This is a non-blocking method and does not guarantee that the operations have changed when this
* this method returns. * method returns.
* *
* @param key the key for which operations have to be changed. * @param key the key for which operations have to be changed.
* @param interestedOps the new interest operations. * @param interestedOps the new interest operations.
*/ */
public void changeOps(SelectionKey key, int interestedOps) { public void changeOps(SelectionKey key, int interestedOps) {
pendingCommands.add(new ChangeKeyOpsCommand(key, interestedOps)); pendingCommands.add(new ChangeKeyOpsCommand(key, interestedOps));
selector.wakeup(); selector.wakeup();
} }
/** /**
* A command that changes the interested operations of the key provided. * A command that changes the interested operations of the key provided.
*/ */
class ChangeKeyOpsCommand implements Runnable { class ChangeKeyOpsCommand implements Runnable {
private SelectionKey key; private SelectionKey key;
private int interestedOps; private int interestedOps;
public ChangeKeyOpsCommand(SelectionKey key, int interestedOps) { public ChangeKeyOpsCommand(SelectionKey key, int interestedOps) {
this.key = key; this.key = key;
this.interestedOps = interestedOps; this.interestedOps = interestedOps;
} }
public void run() { public void run() {
key.interestOps(interestedOps); key.interestOps(interestedOps);
} }
@Override @Override
public String toString() { public String toString() {
return "Change of ops to: " + interestedOps; return "Change of ops to: " + interestedOps;
} }
} }
} }

131
reactor/src/main/java/com/iluwatar/reactor/framework/NioServerSocketChannel.java
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@ -9,81 +9,82 @@ import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel; import java.nio.channels.SocketChannel;
/** /**
* A wrapper over {@link NioServerSocketChannel} which can read and write data on a {@link SocketChannel}. * A wrapper over {@link NioServerSocketChannel} which can read and write data on a
* {@link SocketChannel}.
* *
* @author npathai * @author npathai
*/ */
public class NioServerSocketChannel extends AbstractNioChannel { public class NioServerSocketChannel extends AbstractNioChannel {
private int port; private final int port;
/** /**
* Creates a {@link ServerSocketChannel} which will bind at provided port and use * Creates a {@link ServerSocketChannel} which will bind at provided port and use
* <code>handler</code> to handle incoming events on this channel. * <code>handler</code> to handle incoming events on this channel.
* <p> * <p>
* Note the constructor does not bind the socket, {@link #bind()} method should be called for binding * Note the constructor does not bind the socket, {@link #bind()} method should be called for
* the socket. * binding the socket.
* *
* @param port the port on which channel will be bound to accept incoming connection requests. * @param port the port on which channel will be bound to accept incoming connection requests.
* @param handler the handler that will handle incoming requests on this channel. * @param handler the handler that will handle incoming requests on this channel.
* @throws IOException if any I/O error occurs. * @throws IOException if any I/O error occurs.
*/ */
public NioServerSocketChannel(int port, ChannelHandler handler) throws IOException { public NioServerSocketChannel(int port, ChannelHandler handler) throws IOException {
super(handler, ServerSocketChannel.open()); super(handler, ServerSocketChannel.open());
this.port = port; this.port = port;
} }
@Override @Override
public int getInterestedOps() { public int getInterestedOps() {
// being a server socket channel it is interested in accepting connection from remote peers. // being a server socket channel it is interested in accepting connection from remote peers.
return SelectionKey.OP_ACCEPT; return SelectionKey.OP_ACCEPT;
} }
/** /**
* @return the underlying {@link ServerSocketChannel}. * @return the underlying {@link ServerSocketChannel}.
*/ */
@Override @Override
public ServerSocketChannel getChannel() { public ServerSocketChannel getChannel() {
return (ServerSocketChannel) super.getChannel(); return (ServerSocketChannel) super.getChannel();
} }
/** /**
* Reads and returns {@link ByteBuffer} from the underlying {@link SocketChannel} represented by * Reads and returns {@link ByteBuffer} from the underlying {@link SocketChannel} represented by
* the <code>key</code>. Due to the fact that there is a dedicated channel for each client connection * the <code>key</code>. Due to the fact that there is a dedicated channel for each client
* we don't need to store the sender. * connection we don't need to store the sender.
*/ */
@Override @Override
public ByteBuffer read(SelectionKey key) throws IOException { public ByteBuffer read(SelectionKey key) throws IOException {
SocketChannel socketChannel = (SocketChannel) key.channel(); SocketChannel socketChannel = (SocketChannel) key.channel();
ByteBuffer buffer = ByteBuffer.allocate(1024); ByteBuffer buffer = ByteBuffer.allocate(1024);
int read = socketChannel.read(buffer); int read = socketChannel.read(buffer);
buffer.flip(); buffer.flip();
if (read == -1) { if (read == -1) {
throw new IOException("Socket closed"); throw new IOException("Socket closed");
} }
return buffer; return buffer;
} }
/** /**
* Binds TCP socket on the provided <code>port</code>. * Binds TCP socket on the provided <code>port</code>.
* *
* @throws IOException if any I/O error occurs. * @throws IOException if any I/O error occurs.
*/ */
@Override @Override
public void bind() throws IOException { public void bind() throws IOException {
((ServerSocketChannel)getChannel()).socket().bind(new InetSocketAddress(InetAddress.getLocalHost(), port)); ((ServerSocketChannel) getChannel()).socket().bind(new InetSocketAddress(InetAddress.getLocalHost(), port));
((ServerSocketChannel)getChannel()).configureBlocking(false); ((ServerSocketChannel) getChannel()).configureBlocking(false);
System.out.println("Bound TCP socket at port: " + port); System.out.println("Bound TCP socket at port: " + port);
} }
/** /**
* Writes the pending {@link ByteBuffer} to the underlying channel sending data to * Writes the pending {@link ByteBuffer} to the underlying channel sending data to the intended
* the intended receiver of the packet. * receiver of the packet.
*/ */
@Override @Override
protected void doWrite(Object pendingWrite, SelectionKey key) throws IOException { protected void doWrite(Object pendingWrite, SelectionKey key) throws IOException {
ByteBuffer pendingBuffer = (ByteBuffer) pendingWrite; ByteBuffer pendingBuffer = (ByteBuffer) pendingWrite;
((SocketChannel)key.channel()).write(pendingBuffer); ((SocketChannel) key.channel()).write(pendingBuffer);
} }
} }

47
reactor/src/main/java/com/iluwatar/reactor/framework/SameThreadDispatcher.java
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@ -4,8 +4,8 @@ import java.nio.channels.SelectionKey;
/** /**
* Dispatches the events in the context of caller thread. This implementation is a good fit for * Dispatches the events in the context of caller thread. This implementation is a good fit for
* small applications where there are limited clients. Using this implementation limits the scalability * small applications where there are limited clients. Using this implementation limits the
* because the I/O thread performs the application specific processing. * scalability because the I/O thread performs the application specific processing.
* *
* <p> * <p>
* For better performance use {@link ThreadPoolDispatcher}. * For better performance use {@link ThreadPoolDispatcher}.
@ -16,28 +16,25 @@ import java.nio.channels.SelectionKey;
*/ */
public class SameThreadDispatcher implements Dispatcher { public class SameThreadDispatcher implements Dispatcher {
/** /**
* Dispatches the read event in the context of caller thread. * Dispatches the read event in the context of caller thread. <br/>
* <br/> * Note this is a blocking call. It returns only after the associated handler has handled the read
* Note this is a blocking call. It returns only after the associated handler has handled the * event.
* read event. */
*/ @Override
@Override public void onChannelReadEvent(AbstractNioChannel channel, Object readObject, SelectionKey key) {
public void onChannelReadEvent(AbstractNioChannel channel, Object readObject, SelectionKey key) { /*
if (channel.getHandler() != null) { * Calls the associated handler to notify the read event where application specific code
/* * resides.
* Calls the associated handler to notify the read event where application specific code */
* resides. channel.getHandler().handleChannelRead(channel, readObject, key);
*/ }
channel.getHandler().handleChannelRead(channel, readObject, key);
}
}
/** /**
* No resources to free. * No resources to free.
*/ */
@Override @Override
public void stop() { public void stop() {
// no-op // no-op
} }
} }

71
reactor/src/main/java/com/iluwatar/reactor/framework/ThreadPoolDispatcher.java
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@ -6,50 +6,45 @@ import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit; import java.util.concurrent.TimeUnit;
/** /**
* An implementation that uses a pool of worker threads to dispatch the events. This provides * An implementation that uses a pool of worker threads to dispatch the events. This provides better
* better scalability as the application specific processing is not performed in the context * scalability as the application specific processing is not performed in the context of I/O
* of I/O (reactor) thread. * (reactor) thread.
* *
* @author npathai * @author npathai
* *
*/ */
public class ThreadPoolDispatcher extends SameThreadDispatcher { public class ThreadPoolDispatcher implements Dispatcher {
private ExecutorService executorService; private final ExecutorService executorService;
/** /**
* Creates a pooled dispatcher with tunable pool size. * Creates a pooled dispatcher with tunable pool size.
* *
* @param poolSize number of pooled threads * @param poolSize number of pooled threads
*/ */
public ThreadPoolDispatcher(int poolSize) { public ThreadPoolDispatcher(int poolSize) {
this.executorService = Executors.newFixedThreadPool(poolSize); this.executorService = Executors.newFixedThreadPool(poolSize);
} }
/** /**
* Submits the work of dispatching the read event to worker pool, where it gets picked * Submits the work of dispatching the read event to worker pool, where it gets picked up by
* up by worker threads. * worker threads. <br/>
* <br/> * Note that this is a non-blocking call and returns immediately. It is not guaranteed that the
* Note that this is a non-blocking call and returns immediately. It is not guaranteed * event has been handled by associated handler.
* that the event has been handled by associated handler. */
*/ @Override
@Override public void onChannelReadEvent(AbstractNioChannel channel, Object readObject, SelectionKey key) {
public void onChannelReadEvent(AbstractNioChannel channel, Object readObject, SelectionKey key) { executorService.execute(() -> channel.getHandler().handleChannelRead(channel, readObject, key));
executorService.execute(() -> }
ThreadPoolDispatcher.super.onChannelReadEvent(channel, readObject, key));
}
/**
* Stops the pool of workers.
*/
@Override
public void stop() {
executorService.shutdownNow();
try {
executorService.awaitTermination(4, TimeUnit.SECONDS);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
/**
* Stops the pool of workers.
*
* @throws InterruptedException if interrupted while stopping pool of workers.
*/
@Override
public void stop() throws InterruptedException {
executorService.shutdown();
executorService.awaitTermination(4, TimeUnit.SECONDS);
}
} }

42
reactor/src/test/java/com/iluwatar/reactor/app/AppTest.java
View File

@ -4,24 +4,38 @@ import java.io.IOException;
import org.junit.Test; import org.junit.Test;
/**
*
* This class tests the Distributed Logging service by starting a Reactor and then sending it
* concurrent logging requests using multiple clients.
*
* @author npathai
*/
public class AppTest { public class AppTest {
@Test /**
public void testApp() throws IOException { * Test the application.
App app = new App(); *
app.start(); * @throws IOException if any I/O error occurs.
* @throws InterruptedException if interrupted while stopping the application.
*/
@Test
public void testApp() throws IOException, InterruptedException {
App app = new App();
app.start();
AppClient client = new AppClient(); AppClient client = new AppClient();
client.start(); client.start();
try { // allow clients to send requests. Artificial delay.
Thread.sleep(2000); try {
} catch (InterruptedException e) { Thread.sleep(2000);
e.printStackTrace(); } catch (InterruptedException e) {
} e.printStackTrace();
}
client.stop(); client.stop();
app.stop(); app.stop();
} }
} }