Added a discovery support by listening to UDP.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@15122 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/UDPBroadcastThread.java

+/*
+ * The MIT License
+ *
+ * Copyright (c) 2004-2009, Sun Microsystems, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package hudson;
+
+import hudson.model.Hudson;
+
+import java.io.IOException;
+import java.net.InetSocketAddress;
+import java.net.SocketAddress;
+import java.nio.ByteBuffer;
+import java.nio.channels.ClosedByInterruptException;
+import java.nio.channels.DatagramChannel;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+/**
+ * Monitors a UDP broadcast and respond with the location of the Hudson service.
+ *
+ * <p>
+ * Useful for auto-discovery of Hudson in the network.
+ *
+ * @author Kohsuke Kawaguchi
+ */
+public class UDPBroadcastThread extends Thread {
+    private final Hudson hudson;
+    public UDPBroadcastThread(Hudson hudson) {
+        super("Hudson UDP "+PORT+" monitoring thread");
+        this.hudson = hudson;
+    }
+
+    @Override
+    public void run() {
+        try {
+            DatagramChannel ch = DatagramChannel.open();
+            try {
+                ch.socket().bind(new InetSocketAddress(PORT));
+
+                ByteBuffer b = ByteBuffer.allocate(2048);
+                while(true) {
+                    // the only thing that matters here is who sent it, not what was sent.
+                    SocketAddress sender = ch.receive(b);
+
+                    // prepare a response
+                    TcpSlaveAgentListener tal = hudson.getTcpSlaveAgentListener();
+
+                    StringBuilder buf = new StringBuilder("<hudson>");
+                    tag(buf,"version",Hudson.VERSION);
+                    tag(buf,"url",hudson.getRootUrl());
+                    tag(buf,"slave-port",tal==null?null:tal.getPort());
+                    buf.append("</hudson>");
+
+                    b.clear();
+                    b.put(buf.toString().getBytes("UTF-8"));
+                    b.flip();
+                    ch.send(b, sender);
+                }
+            } finally {
+                ch.close();
+            }
+        } catch (ClosedByInterruptException e) {
+            // shut down
+        } catch (IOException e) {
+            LOGGER.log(Level.WARNING, "UDP handling problem",e);
+        }
+    }
+
+    private void tag(StringBuilder buf, String tag, Object value) {
+        if(value==null) return;
+        buf.append('<').append(tag).append('>').append(value).append("</").append(tag).append('>');
+    }
+
+    public void shutdown() {
+        interrupt();
+    }
+
+    public static final int PORT = Integer.getInteger("hudson.udp",33848);
+
+    private static final Logger LOGGER = Logger.getLogger(UDPBroadcastThread.class.getName());
+}

core/src/main/java/hudson/model/Hudson.java

@@ -39,6 +39,7 @@ import hudson.Util;
 import static hudson.Util.fixEmpty;
 import hudson.WebAppMain;
 import hudson.XmlFile;
+import hudson.UDPBroadcastThread;
 import hudson.logging.LogRecorderManager;
 import hudson.lifecycle.WindowsInstallerLink;
 import hudson.lifecycle.Lifecycle;
@@ -330,6 +331,8 @@ public final class Hudson extends AbstractModelObject implements ItemGroup<TopLe
 
     public transient volatile TcpSlaveAgentListener tcpSlaveAgentListener;
 
+    private transient UDPBroadcastThread udpBroadcastThread;
+
     /**
      * List of registered {@link JobListener}s.
      */
@@ -497,6 +500,9 @@ public final class Hudson extends AbstractModelObject implements ItemGroup<TopLe
         else
             tcpSlaveAgentListener = null;
 
+        udpBroadcastThread = new UDPBroadcastThread(this);
+        udpBroadcastThread.start();
+
         updateComputerList();
 
         getQueue().load();
@@ -1804,6 +1810,7 @@ public final class Hudson extends AbstractModelObject implements ItemGroup<TopLe
             c.kill();
             pending.add(c.disconnect());
         }
+        udpBroadcastThread.shutdown();
         ExternalJob.reloadThread.interrupt();
         Trigger.timer.cancel();
         // TODO: how to wait for the completion of the last job?

test/src/test/java/hudson/UDPBroadcastThreadTest.java

+package hudson;
+
+import org.jvnet.hudson.test.HudsonTestCase;
+import org.xml.sax.InputSource;
+import org.xml.sax.helpers.DefaultHandler;
+
+import javax.xml.parsers.SAXParserFactory;
+import java.net.DatagramSocket;
+import java.net.DatagramPacket;
+import java.net.InetAddress;
+import java.io.StringReader;
+
+/**
+ * @author Kohsuke Kawaguchi
+ */
+public class UDPBroadcastThreadTest extends HudsonTestCase {
+    public void test1() throws Exception {
+        DatagramSocket s = new DatagramSocket();
+        DatagramPacket p = new DatagramPacket(new byte[1024],1024);
+        p.setAddress(InetAddress.getLocalHost());
+        p.setPort(UDPBroadcastThread.PORT);
+        s.send(p);
+        s.setSoTimeout(5000); // to prevent test hang
+
+        s.receive(p);
+        String xml = new String(p.getData(), 0, p.getLength(), "UTF-8");
+        System.out.println(xml);
+
+        // make sure at least this XML parses
+        SAXParserFactory spf = SAXParserFactory.newInstance();
+        spf.setNamespaceAware(true);
+        spf.newSAXParser().parse(new InputSource(new StringReader(xml)),new DefaultHandler());
+    }
+}