[FIXED JENKINS-23481][FIXED JENKINS-23551] Send onOffline notification to...

[FIXED JENKINS-23481][FIXED JENKINS-23551] Send onOffline notification to master computer prior Jenkins restart.

Introduces new overload `ComputerListener.onOffline(Computer, OfflineCause)`.

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

@@ -36,6 +36,9 @@ import hudson.AbortException;
 
 import java.io.IOException;
 
+import javax.annotation.CheckForNull;
+import javax.annotation.Nonnull;
+
 /**
  * Receives notifications about status changes of {@link Computer}s.
  *
@@ -161,9 +164,21 @@ public abstract class ComputerListener implements ExtensionPoint {
 
     /**
      * Called right after a {@link Computer} went offline.
+     *
+     * @deprecated since TODO. Use {@link #onOffline(Computer, OfflineCause)} instead.
      */
+    @Deprecated
     public void onOffline(Computer c) {}
 
+    /**
+     * Called right after a {@link Computer} went offline.
+     *
+     * @since TODO
+     */
+    public void onOffline(@Nonnull Computer c, @CheckForNull OfflineCause cause) {
+        onOffline(c);
+    }
+
     /**
      * Indicates that the computer was marked as temporarily online by the administrator.
      * This is the reverse operation of {@link #onTemporarilyOffline(Computer, OfflineCause)}

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

@@ -55,7 +55,10 @@ public abstract class OfflineCause {
     public static class SimpleOfflineCause extends OfflineCause {
         public final Localizable description;
 
-        private SimpleOfflineCause(Localizable description) {
+        /**
+         * @since TODO
+         */
+        protected SimpleOfflineCause(Localizable description) {
             this.description = description;
         }
 

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

@@ -625,7 +625,7 @@ public class SlaveComputer extends Computer {
                 logger.log(Level.SEVERE, "Failed to terminate channel to " + getDisplayName(), e);
             }
             for (ComputerListener cl : ComputerListener.all())
-                cl.onOffline(this);
+                cl.onOffline(this, offlineCause);
         }
     }
 

core/src/main/java/jenkins/model/Jenkins.java

@@ -3329,6 +3329,31 @@ public class Jenkins extends AbstractCIBase implements DirectlyModifiableTopLeve
         }.start();
     }
 
+    @Extension @Restricted(NoExternalUse.class)
+    public static class MasterRestartNotifyier extends RestartListener {
+
+        @Override
+        public void onRestart() {
+            Computer computer = Jenkins.getInstance().toComputer();
+            if (computer == null) return;
+            RestartCause cause = new RestartCause();
+            for (ComputerListener listener: ComputerListener.all()) {
+                listener.onOffline(computer, cause);
+            }
+        }
+
+        @Override
+        public boolean isReadyToRestart() throws IOException, InterruptedException {
+            return true;
+        }
+
+        private static class RestartCause extends OfflineCause.SimpleOfflineCause {
+            protected RestartCause() {
+                super(Messages._Jenkins_IsRestarting());
+            }
+        }
+    }
+
     /**
      * Shutdown the system.
      * @since 1.161

core/src/main/resources/hudson/model/Messages.properties

@@ -359,3 +359,4 @@ Jenkins.CheckDisplayName.NameNotUniqueWarning=The display name, "{0}", is used a
 Jenkins.CheckDisplayName.DisplayNameNotUniqueWarning=The display name, "{0}", is already in use by another job and could cause confusion and delay.
 
 Jenkins.NotAllowedName="{0}" is not allowed name
+Jenkins.IsRestarting=Jenkins is restarting