Added a new extension point that allows plugins to postpone the restart.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@34846 71c3de6d-444a-0410-be80-ed276b4c234a

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

@@ -2474,7 +2474,7 @@ public final class Hudson extends Node implements ItemGroup<TopLevelItem>, Stapl
         doQuietDown().generateResponse(null,rsp,this);
     }
 
-    public synchronized HttpRedirect doQuietDown() {
+    public synchronized HttpRedirect doQuietDown() throws IOException {
         try {
             return doQuietDown(false,0);
         } catch (InterruptedException e) {
@@ -2485,7 +2485,7 @@ public final class Hudson extends Node implements ItemGroup<TopLevelItem>, Stapl
     @CLIMethod(name="quiet-down")
     public HttpRedirect doQuietDown(
             @Option(name="-block",usage="Block until the system really quiets down and no builds are running") @QueryParameter boolean block,
-            @Option(name="-timeout",usage="If non-zero, only block up to the specified number of milliseconds") @QueryParameter int timeout) throws InterruptedException {
+            @Option(name="-timeout",usage="If non-zero, only block up to the specified number of milliseconds") @QueryParameter int timeout) throws InterruptedException, IOException {
         synchronized (this) {
             checkPermission(ADMINISTER);
             isQuietingDown = true;
@@ -2493,8 +2493,8 @@ public final class Hudson extends Node implements ItemGroup<TopLevelItem>, Stapl
         if (block) {
             if (timeout > 0) timeout += System.currentTimeMillis();
             while (isQuietingDown
-                   && (overallLoad.computeTotalExecutors() > overallLoad.computeIdleExecutors())
-                   && (timeout <= 0 || System.currentTimeMillis() < timeout)) {
+                   && (timeout <= 0 || System.currentTimeMillis() < timeout)
+                   && RestartListener.isAllReady()) {
                 Thread.sleep(1000);
             }
         }
@@ -2958,6 +2958,8 @@ public final class Hudson extends Node implements ItemGroup<TopLevelItem>, Stapl
                     // give some time for the browser to load the "reloading" page
                     Thread.sleep(5000);
                     LOGGER.severe(String.format("Restarting VM as requested by %s",exitUser));
+                    for (RestartListener listener : RestartListener.all())
+                        listener.onRestart();
                     lifecycle.restart();
                 } catch (InterruptedException e) {
                     LOGGER.log(Level.WARNING, "Failed to restart Hudson",e);
@@ -2995,6 +2997,8 @@ public final class Hudson extends Node implements ItemGroup<TopLevelItem>, Stapl
                         LOGGER.info("Restart in 10 seconds");
                         Thread.sleep(10000);
                         LOGGER.severe(String.format("Restarting VM as requested by %s",exitUser));
+                        for (RestartListener listener : RestartListener.all())
+                            listener.onRestart();
                         lifecycle.restart();
                     } else {
                         LOGGER.info("Safe-restart mode cancelled");

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

+package hudson.model;
+
+import hudson.Extension;
+import hudson.ExtensionList;
+import hudson.ExtensionPoint;
+
+import java.io.IOException;
+
+/**
+ * Extension point that allows plugins to veto the restart.
+ *
+ * @author Kohsuke Kawaguchi
+ * @since 1.376
+ */
+public abstract class RestartListener implements ExtensionPoint {
+    /**
+     * Called periodically during the safe restart.
+     *
+     * @return false to block the restart
+     */
+    public abstract boolean isReadyToRestart() throws IOException, InterruptedException;
+
+    /**
+     * Called immediately before the restart is actually triggered.
+     */
+    public void onRestart() {}
+
+    /**
+     * Returns all the registered {@link LabelFinder}s.
+     */
+    public static ExtensionList<RestartListener> all() {
+        return Hudson.getInstance().getExtensionList(RestartListener.class);
+    }
+
+    /**
+     * Returns true iff all the listeners OKed the restart.
+     */
+    public static boolean isAllReady() throws IOException, InterruptedException {
+        for (RestartListener listener : all()) {
+            if (!listener.isReadyToRestart())
+                return false;
+        }
+        return true;
+    }
+
+    /**
+     * Default logic. Wait for all the executors to become idle.
+     */
+    @Extension
+    public static class Default extends RestartListener {
+        @Override
+        public boolean isReadyToRestart() throws IOException, InterruptedException {
+            Hudson h = Hudson.getInstance();
+            return h.overallLoad.computeTotalExecutors() <= h.overallLoad.computeIdleExecutors();
+        }
+    }
+}