[JENKINS-38370] Start defining APIs that are for the master JVM only

core/src/main/java/hudson/ExtensionList.java

@@ -46,6 +46,7 @@
 import java.util.logging.Logger;
 import javax.annotation.CheckForNull;
 import javax.annotation.Nonnull;
+import jenkins.util.io.OnMaster;
 
 /**
  * Retains the known extension instances for the given type 'T'.
@@ -68,7 +69,7 @@
  * @see jenkins.model.Jenkins#getExtensionList(Class)
  * @see jenkins.model.Jenkins#getDescriptorList(Class)
  */
-public class ExtensionList<T> extends AbstractList<T> {
+public class ExtensionList<T> extends AbstractList<T> implements OnMaster {
     /**
      * @deprecated as of 1.417
      *      Use {@link #jenkins}

core/src/main/java/hudson/ExtensionPoint.java

@@ -29,6 +29,7 @@
 import java.lang.annotation.Retention;
 import static java.lang.annotation.RetentionPolicy.RUNTIME;
 import java.lang.annotation.Target;
+import jenkins.util.io.OnMaster;
 
 /**
  * Marker interface that designates extensible components
@@ -47,7 +48,7 @@
  * @see Plugin
  * @see Extension
  */
-public interface ExtensionPoint {
+public interface ExtensionPoint extends OnMaster {
     /**
      * Used by designers of extension points (direct subtypes of {@link ExtensionPoint}) to indicate that
      * the legacy instances are scoped to {@link Jenkins} instance. By default, legacy instances are

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

@@ -39,6 +39,7 @@
 import jenkins.model.GlobalConfiguration;
 import jenkins.model.GlobalConfigurationCategory;
 import jenkins.model.Jenkins;
+import jenkins.util.io.OnMaster;
 import net.sf.json.JSONArray;
 import net.sf.json.JSONObject;
 import org.kohsuke.stapler.*;
@@ -125,7 +126,7 @@
  * @author Kohsuke Kawaguchi
  * @see Describable
  */
-public abstract class Descriptor<T extends Describable<T>> implements Saveable {
+public abstract class Descriptor<T extends Describable<T>> implements Saveable, OnMaster {
     /**
      * The class being described by this descriptor.
      */

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

@@ -27,6 +27,7 @@
 import hudson.Functions;
 import jenkins.util.SystemProperties;
 import hudson.security.PermissionScope;
+import jenkins.util.io.OnMaster;
 import org.kohsuke.stapler.StaplerRequest;
 
 import java.io.IOException;
@@ -67,7 +68,7 @@
  * @see Items
  * @see ItemVisitor
  */
-public interface Item extends PersistenceRoot, SearchableModelObject, AccessControlled {
+public interface Item extends PersistenceRoot, SearchableModelObject, AccessControlled, OnMaster {
     /**
      * Gets the parent that contains this item.
      */

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

@@ -128,7 +128,7 @@
  * @author Kohsuke Kawaguchi
  */
 public abstract class Job<JobT extends Job<JobT, RunT>, RunT extends Run<JobT, RunT>>
-        extends AbstractItem implements ExtensionPoint, StaplerOverridable, ModelObjectWithChildren, OnMaster {
+        extends AbstractItem implements ExtensionPoint, StaplerOverridable, ModelObjectWithChildren {
 
     private static final Logger LOGGER = Logger.getLogger(Job.class.getName());
 

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

@@ -212,6 +212,7 @@
 import jenkins.util.JenkinsJVM;
 import jenkins.util.Timer;
 import jenkins.util.io.FileBoolean;
+import jenkins.util.io.OnMaster;
 import jenkins.util.xml.XMLUtils;
 import net.jcip.annotations.GuardedBy;
 import net.sf.json.JSONObject;
@@ -323,7 +324,7 @@
 @ExportedBean
 public class Jenkins extends AbstractCIBase implements DirectlyModifiableTopLevelItemGroup, StaplerProxy, StaplerFallback,
         ModifiableViewGroup, AccessControlled, DescriptorByNameOwner,
-        ModelObjectWithContextMenu, ModelObjectWithChildren {
+        ModelObjectWithContextMenu, ModelObjectWithChildren, OnMaster {
     private transient final Queue queue;
 
     /**

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

@@ -16,4 +16,36 @@
  * @since 1.475
  */
 public interface OnMaster {
+// TODO uncomment once we can have a delegating ClassFilter, also add SystemProperty to toggle feature
+//    @Extension
+//    @Restricted(NoExternalUse.class)
+//    class ChannelConfiguratorImpl extends ChannelConfigurator {
+//        @Override
+//        public void onChannelBuilding(ChannelBuilder builder, @Nullable Object context) {
+//            if (context instanceof SlaveComputer) {
+//                builder.withClassFilter(new ClassFilterImpl(builder.getClassFilter(), OnMaster.class.getName, ...));
+//            }
+//        }
+//    }
+//
+//    @Restricted(NoExternalUse.class)
+//    class ClassFilterImpl extends ClassFilter {
+//        private final ClassFilter delegate;
+//        private final Set<String> blacklist;
+//
+//        public ClassFilterImpl(ClassFilter delegate, String... blacklist) {
+//            this.blacklist = new HashSet<>(blacklist);
+//            this.delegate = delegate;
+//        }
+//
+//        @Override
+//        protected boolean isBlacklisted(String name) {
+//            return blacklist.contains(name) || delegate.isBlacklisted(name);
+//        }
+//
+//        @Override
+//        protected boolean isBlacklisted(Class c) {
+//            return c.getAnnotation(MasterJVMOnly.class) != null || delegate.isBlacklisted(c);
+//        }
+//    }
 }