Added additional event hooks.

- Pass TaskListener to enable listeners to report what they are doing
- Added another callback to report a failure

changelog.html

@@ -66,6 +66,9 @@ Upcoming changes</a>
   <li class=rfe>
     Proactively watch out for incomplete extensions to avoid cryptic NPE.
     (<a href="http://issues.jenkins-ci.org/browse/JENKINS-8866">issue 8866</a>)
+  <li class=rfe>
+    Added more event callbacks on <tt>ComputerListener</tt>
+    (<a href="http://jenkins.361315.n4.nabble.com/Hooking-into-failed-slave-launches-td3339646.html">thread</a>)
 </ul>
 </div><!--=TRUNK-END=-->
 

core/src/main/java/hudson/slaves/ComputerListener.java

@@ -44,20 +44,43 @@ import java.io.IOException;
  */
 public abstract class ComputerListener implements ExtensionPoint {
     /**
-     * Called before a {@link Computer} is brought online.
+     * Called before a {@link ComputerLauncher} is asked to launch a connection with {@link Computer}.
      *
      * <p>
      * This enables you to do some configurable checks to see if we
      * want to bring this slave online or if there are considerations
      * that would keep us from doing so.
      *
+     * <p>
+     * Throwing {@link AbortException} would let you veto the launch operation. Other thrown exceptions
+     * will also have the same effect, but their stack trace will be dumped, so they are meant for error situation.
+     *
+     * @param c
+     *      Computer that's being launched. Never null.
+     * @param taskListener
+     *      Connected to the slave console log. Useful for reporting progress/errors on a lengthy operation.
+     *      Never null.
      * @throws AbortException
      *      Exceptions will be recorded to the listener, and
      *      the computer will not become online.
      *
-     * @since 1.400
+     * @since 1.402
+     */
+    public void preLaunch(Computer c, TaskListener taskListener) throws IOException, InterruptedException {
+    }
+
+    /**
+     * Called when a slave attempted to connect via {@link ComputerLauncher} but it failed.
+     *
+     * @param c
+     *      Computer that was trying to launch. Never null.
+     * @param taskListener
+     *      Connected to the slave console log. Useful for reporting progress/errors on a lengthy operation.
+     *      Never null.
+     *
+     * @since 1.402
      */
-    public void allowOnline(Computer c) throws AbortException {
+    public void onLaunchFailure(Computer c, TaskListener taskListener) throws IOException, InterruptedException {
     }
 
     /**

core/src/main/java/hudson/slaves/SlaveComputer.java

@@ -192,7 +192,7 @@ public class SlaveComputer extends Computer {
                     log.rewind();
                     try {
                         for (ComputerListener cl : ComputerListener.all())
-                            cl.allowOnline(SlaveComputer.this);
+                            cl.preLaunch(SlaveComputer.this, taskListener);
                         launcher.launch(SlaveComputer.this, taskListener);
                         return null;
                     } catch (AbortException e) {
@@ -207,8 +207,11 @@ public class SlaveComputer extends Computer {
                         throw e;
                     }
                 } finally {
-                    if (channel==null)
+                    if (channel==null) {
                         offlineCause = new OfflineCause.LaunchFailed();
+                        for (ComputerListener cl : ComputerListener.all())
+                            cl.onLaunchFailure(SlaveComputer.this, taskListener);
+                    }
                 }
             }
         });