run this asynchronously so that slaves can be used right away

core/src/main/java/jenkins/slaves/restarter/JnlpSlaveRestarterInstaller.java

@@ -9,6 +9,7 @@ import hudson.remoting.EngineListener;
 import hudson.remoting.EngineListenerAdapter;
 import hudson.remoting.VirtualChannel;
 import hudson.slaves.ComputerListener;
+import jenkins.model.Jenkins.MasterComputer;
 
 import java.io.IOException;
 import java.io.Serializable;
@@ -31,62 +32,68 @@ import static java.util.logging.Level.*;
 @Extension
 public class JnlpSlaveRestarterInstaller extends ComputerListener implements Serializable {
     @Override
-    public void onOnline(Computer c, TaskListener listener) throws IOException, InterruptedException {
-        final List<SlaveRestarter> restarters = new ArrayList<SlaveRestarter>(SlaveRestarter.all());
+    public void onOnline(final Computer c, final TaskListener listener) throws IOException, InterruptedException {
+        MasterComputer.threadPoolForRemoting.submit(new java.util.concurrent.Callable<Object>() {
+            @Override
+            public Object call() throws Exception {
+                final List<SlaveRestarter> restarters = new ArrayList<SlaveRestarter>(SlaveRestarter.all());
 
-        VirtualChannel ch = c.getChannel();
-        if (ch==null)   return; // defensive check
+                VirtualChannel ch = c.getChannel();
+                if (ch==null)   return null; // defensive check
 
-        List<SlaveRestarter> effective = null;
-        try {
-            effective = ch.call(new Callable<List<SlaveRestarter>, IOException>() {
-                public List<SlaveRestarter> call() throws IOException {
-                    Engine e = Engine.current();
-                    if (e == null) return null;    // not running under Engine
+                List<SlaveRestarter> effective = null;
+                try {
+                    effective = ch.call(new Callable<List<SlaveRestarter>, IOException>() {
+                        public List<SlaveRestarter> call() throws IOException {
+                            Engine e = Engine.current();
+                            if (e == null) return null;    // not running under Engine
 
-                    try {
-                        Engine.class.getMethod("addListener", EngineListener.class);
-                    } catch (NoSuchMethodException _) {
-                        return null;    // running with older version of remoting that doesn't support adding listener
-                    }
+                            try {
+                                Engine.class.getMethod("addListener", EngineListener.class);
+                            } catch (NoSuchMethodException _) {
+                                return null;    // running with older version of remoting that doesn't support adding listener
+                            }
 
-                    // filter out ones that doesn't apply
-                    for (Iterator<SlaveRestarter> itr = restarters.iterator(); itr.hasNext(); ) {
-                        SlaveRestarter r =  itr.next();
-                        if (!r.canWork())
-                            itr.remove();
-                    }
+                            // filter out ones that doesn't apply
+                            for (Iterator<SlaveRestarter> itr = restarters.iterator(); itr.hasNext(); ) {
+                                SlaveRestarter r =  itr.next();
+                                if (!r.canWork())
+                                    itr.remove();
+                            }
 
-                    e.addListener(new EngineListenerAdapter() {
-                        @Override
-                        public void onDisconnect() {
-                            try {
-                                for (SlaveRestarter r : restarters) {
+                            e.addListener(new EngineListenerAdapter() {
+                                @Override
+                                public void onDisconnect() {
                                     try {
-                                        LOGGER.info("Restarting slave via "+r);
-                                        r.restart();
-                                    } catch (Exception x) {
-                                        LOGGER.log(SEVERE, "Failed to restart slave with "+r, x);
+                                        for (SlaveRestarter r : restarters) {
+                                            try {
+                                                LOGGER.info("Restarting slave via "+r);
+                                                r.restart();
+                                            } catch (Exception x) {
+                                                LOGGER.log(SEVERE, "Failed to restart slave with "+r, x);
+                                            }
+                                        }
+                                    } finally {
+                                        // if we move on to the reconnection without restart,
+                                        // don't let the current implementations kick in when the slave loses connection again
+                                        restarters.clear();
                                     }
                                 }
-                            } finally {
-                                // if we move on to the reconnection without restart,
-                                // don't let the current implementations kick in when the slave loses connection again
-                                restarters.clear();
-                            }
+                            });
+
+                            return restarters;
                         }
                     });
-
-                    return restarters;
+                } catch (IOException e) {
+                    e.printStackTrace(listener.error("Failed to install restarter"));
+                    // don't let this fail the slave connection
                 }
-            });
-        } catch (IOException e) {
-            e.printStackTrace(listener.error("Failed to install restarter"));
-            // don't let this fail the slave connection
-        }
 
-        // TODO: report this to GUI
-        listener.getLogger().println("Effective SlaveRestarter on "+c.getDisplayName()+": "+effective);
+                // TODO: report this to GUI
+                listener.getLogger().println("Effective SlaveRestarter on " + c.getDisplayName() + ": " + effective);
+                return null;
+            }
+        });
     }
 
     private static final Logger LOGGER = Logger.getLogger(JnlpSlaveRestarterInstaller.class.getName());