added a marker interface to help plugin developers.

core/src/main/java/hudson/PluginManager.java

@@ -46,6 +46,7 @@ import jenkins.InitReactorRunner;
 import jenkins.RestartRequiredException;
 import jenkins.YesNoMaybe;
 import jenkins.model.Jenkins;
+import jenkins.util.io.OnMaster;
 import org.apache.commons.fileupload.FileItem;
 import org.apache.commons.fileupload.disk.DiskFileItemFactory;
 import org.apache.commons.fileupload.servlet.ServletFileUpload;
@@ -99,7 +100,7 @@ import static hudson.init.InitMilestone.*;
  * @author Kohsuke Kawaguchi
  */
 @ExportedBean
-public abstract class PluginManager extends AbstractModelObject {
+public abstract class PluginManager extends AbstractModelObject implements OnMaster {
     /**
      * All discovered plugins.
      */

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

@@ -60,6 +60,7 @@ import hudson.widgets.HistoryWidget.Adapter;
 import hudson.widgets.Widget;
 import jenkins.model.Jenkins;
 import jenkins.model.ProjectNamingStrategy;
+import jenkins.util.io.OnMaster;
 import net.sf.json.JSONException;
 import net.sf.json.JSONObject;
 import org.jfree.chart.ChartFactory;
@@ -102,7 +103,7 @@ import static javax.servlet.http.HttpServletResponse.*;
  * @author Kohsuke Kawaguchi
  */
 public abstract class Job<JobT extends Job<JobT, RunT>, RunT extends Run<JobT, RunT>>
-        extends AbstractItem implements ExtensionPoint, StaplerOverridable {
+        extends AbstractItem implements ExtensionPoint, StaplerOverridable, OnMaster {
 
     /**
      * Next build number. Kept in a separate file because this is the only

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

@@ -59,6 +59,7 @@ import java.util.List;
 import java.util.logging.Logger;
 
 import jenkins.model.Jenkins;
+import jenkins.util.io.OnMaster;
 import net.sf.json.JSONObject;
 import org.kohsuke.stapler.BindInterceptor;
 import org.kohsuke.stapler.Stapler;
@@ -77,7 +78,7 @@ import org.kohsuke.stapler.export.Exported;
  * @see NodeDescriptor
  */
 @ExportedBean
-public abstract class Node extends AbstractModelObject implements ReconfigurableDescribable<Node>, ExtensionPoint, AccessControlled {
+public abstract class Node extends AbstractModelObject implements ReconfigurableDescribable<Node>, ExtensionPoint, AccessControlled, OnMaster {
 
     private static final Logger LOGGER = Logger.getLogger(Node.class.getName());
 

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

@@ -97,6 +97,7 @@ import javax.servlet.ServletException;
 import javax.servlet.http.HttpServletResponse;
 
 import jenkins.model.Jenkins;
+import jenkins.util.io.OnMaster;
 import net.sf.json.JSONObject;
 import org.apache.commons.io.input.NullInputStream;
 import org.apache.commons.io.IOUtils;
@@ -128,7 +129,7 @@ import static java.util.logging.Level.*;
  */
 @ExportedBean
 public abstract class Run <JobT extends Job<JobT,RunT>,RunT extends Run<JobT,RunT>>
-        extends Actionable implements ExtensionPoint, Comparable<RunT>, AccessControlled, PersistenceRoot, DescriptorByNameOwner {
+        extends Actionable implements ExtensionPoint, Comparable<RunT>, AccessControlled, PersistenceRoot, DescriptorByNameOwner, OnMaster {
 
     protected transient final JobT project;
 

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

@@ -47,6 +47,7 @@ import hudson.util.PersistedList;
 import hudson.util.XStream2;
 import jenkins.RestartRequiredException;
 import jenkins.model.Jenkins;
+import jenkins.util.io.OnMaster;
 import org.acegisecurity.Authentication;
 import org.acegisecurity.context.SecurityContext;
 import org.apache.commons.io.input.CountingInputStream;
@@ -104,7 +105,7 @@ import org.kohsuke.stapler.interceptor.RequirePOST;
  * @since 1.220
  */
 @ExportedBean
-public class UpdateCenter extends AbstractModelObject implements Saveable {
+public class UpdateCenter extends AbstractModelObject implements Saveable, OnMaster {
 	
     private static final String UPDATE_CENTER_URL = System.getProperty(UpdateCenter.class.getName()+".updateCenterUrl","http://updates.jenkins-ci.org/");
 	

core/src/main/java/jenkins/util/io/OnMaster.java

+package jenkins.util.io;
+
+/**
+ * Marks the objects in Jenkins that only exist in the core
+ * and not on slaves.
+ *
+ * <p>
+ * This marker interface is for plugin developers to quickly
+ * tell if they can take a specific object from a master to
+ * a slave.
+ *
+ * (Core developers, if you find classes/interfaces that extend
+ * from this, please be encouraged to add them.)
+ *
+ * @author Kohsuke Kawaguchi
+ * @since 1.475
+ */
+public interface OnMaster {
+}