Ensure ClassLoaders have names for debugging

core/src/main/java/hudson/ClassicPluginStrategy.java

@@ -52,6 +52,7 @@
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
+import java.util.UUID;
 import java.util.jar.Attributes;
 import java.util.jar.JarFile;
 import java.util.jar.Manifest;
@@ -235,7 +236,11 @@
         dependencyLoader = getBaseClassLoader(atts, dependencyLoader);
 
         return new PluginWrapper(pluginManager, archive, manifest, baseResourceURL,
-                createClassLoader(paths, dependencyLoader, atts), disableFile, dependencies, optionalDependencies);
+                createClassLoader(computeClassLoaderName(manifest, archive), paths, dependencyLoader, atts), disableFile, dependencies, optionalDependencies);
+    }
+
+    private static String computeClassLoaderName(Manifest mf, File archive) {
+        return "PluginClassLoader for " + PluginWrapper.computeShortName(mf, archive.getName());
     }
 
     private void fix(Attributes atts, List<PluginWrapper.Dependency> optionalDependencies) {
@@ -263,15 +268,28 @@
         return DetachedPluginsUtil.getImpliedDependencies(pluginName, jenkinsVersion);
     }
 
-    @Deprecated
+    /**
+     * @deprecated since TODO use {@link #createClassLoader(String, List, ClassLoader, Attributes)}
+     */
+    @Deprecated(since = "//TODO")
     protected ClassLoader createClassLoader(List<File> paths, ClassLoader parent) throws IOException {
         return createClassLoader(paths, parent, null);
     }
 
     /**
-     * Creates the classloader that can load all the specified jar files and delegate to the given parent.
+     * @deprecated since TODO use {@link #createClassLoader(String, List, ClassLoader, Attributes)}
      */
+    @Deprecated(since="@TODO")
     protected ClassLoader createClassLoader(List<File> paths, ClassLoader parent, Attributes atts) throws IOException {
+        // generate a legacy id so at least we can track to something
+        return createClassLoader("legacy"+UUID.randomUUID(), paths, parent, atts);
+    }
+
+    /**
+     * Creates a  classloader that can load all the specified jar files and delegate to the given parent.
+     * @since //TODO
+     */
+    protected ClassLoader createClassLoader(String name, List<File> paths, ClassLoader parent, Attributes atts) throws IOException {
         boolean usePluginFirstClassLoader =
                 atts != null && Boolean.parseBoolean(atts.getValue("PluginFirstClassLoader"));
 
@@ -285,9 +303,9 @@
         }
         URLClassLoader2 classLoader;
         if (usePluginFirstClassLoader) {
-            classLoader = new PluginFirstClassLoader2(urls.toArray(new URL[0]), parent);
+            classLoader = new PluginFirstClassLoader2(name, urls.toArray(new URL[0]), parent);
         } else {
-            classLoader = new URLClassLoader2(urls.toArray(new URL[0]), parent);
+            classLoader = new URLClassLoader2(name, urls.toArray(new URL[0]), parent);
         }
         return classLoader;
     }
@@ -561,7 +579,7 @@
         }
 
         DependencyClassLoader(ClassLoader parent, File archive, List<Dependency> dependencies, PluginManager pluginManager) {
-            super(parent);
+            super("dependency ClassLoader for " + archive.getPath(), parent);
             this._for = archive;
             this.dependencies = List.copyOf(dependencies);
             this.pluginManager = pluginManager;

core/src/main/java/hudson/PluginFirstClassLoader2.java

@@ -25,8 +25,9 @@ public class PluginFirstClassLoader2 extends URLClassLoader2 {
         registerAsParallelCapable();
     }
 
-    public PluginFirstClassLoader2(@NonNull URL[] urls, @NonNull ClassLoader parent) {
-        super(Objects.requireNonNull(urls), Objects.requireNonNull(parent));
+
+    public PluginFirstClassLoader2(String name, @NonNull URL[] urls, @NonNull ClassLoader parent) {
+        super(name, Objects.requireNonNull(urls), Objects.requireNonNull(parent));
     }
 
     /**

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

@@ -1099,7 +1099,7 @@ protected void copyBundledPlugin(URL src, String fileName) throws IOException {
     }
 
     /*package*/ static @CheckForNull Manifest parsePluginManifest(URL bundledJpi) {
-        try (URLClassLoader cl = new URLClassLoader(new URL[]{bundledJpi})) {
+        try (URLClassLoader cl = new URLClassLoader("Temporary classloader for parsing " + bundledJpi.toString(), new URL[]{bundledJpi}, ClassLoader.getSystemClassLoader())) {
             InputStream in = null;
             try {
                 URL res = cl.findResource(PluginWrapper.MANIFEST_FILENAME);
@@ -2337,7 +2337,7 @@ public static final class UberClassLoader extends ClassLoader {
         }
 
         public UberClassLoader(List<PluginWrapper> activePlugins) {
-            super(PluginManager.class.getClassLoader());
+            super(activePlugins.stream().map(PluginWrapper::getShortName).collect(Collectors.joining(", ", "UberClassLoader for ", "")), PluginManager.class.getClassLoader());
             this.activePlugins = activePlugins;
         }
 

core/src/main/java/hudson/util/MaskingClassLoader.java

@@ -59,7 +59,7 @@ public MaskingClassLoader(ClassLoader parent, String... masks) {
     }
 
     public MaskingClassLoader(ClassLoader parent, Collection<String> masks) {
-        super(parent);
+        super("Masking ClassLoader of " + parent.getName(), parent);
         this.masksClasses = List.copyOf(masks);
 
         /*

core/src/main/java/jenkins/util/URLClassLoader2.java

@@ -17,14 +17,43 @@ public class URLClassLoader2 extends URLClassLoader implements JenkinsClassLoade
         registerAsParallelCapable();
     }
 
+    /**
+     * @deprecated use {@link URLClassLoader2#URLClassLoader2(String, URL[])}
+     */
+    @Deprecated(since = "//TODO")
     public URLClassLoader2(URL[] urls) {
         super(urls);
     }
 
+    /**
+     * @deprecated use {@link URLClassLoader2#URLClassLoader2(String, URL[], ClassLoader)}
+     */
+    @Deprecated(since = "//TODO")
     public URLClassLoader2(URL[] urls, ClassLoader parent) {
         super(urls, parent);
     }
 
+    /**
+     * Create a new {@link URLClassLoader2} with the given name and URLS and the {@link #getSystemClassLoader()} as its parent.
+     * @param name name of this classloader.
+     * @param urls the list of URLS to find classes in.
+     * @since //TODO
+     */
+    public URLClassLoader2(String name, URL[] urls) {
+        super(name, urls, getSystemClassLoader());
+    }
+
+    /**
+     *  Create a new {@link URLClassLoader2} with the given name, URLS parent.
+     * @param name name of this classloader.
+     * @param urls the list of URLS to find classes in.
+     * @param parent the parent to search for classes before we look in the {@code urls}
+     * @since //TODO
+     */
+    public URLClassLoader2(String name, URL[] urls, ClassLoader parent) {
+        super(name, urls, parent);
+    }
+
     @Override
     public void addURL(URL url) {
         super.addURL(url);

core/src/test/java/hudson/PluginWrapperTest.java

@@ -105,7 +105,7 @@ public void dependencyFailedToLoad() {
     @Issue("JENKINS-66563")
     @Test
     public void insertJarsIntoClassPath() throws Exception {
-        try (URLClassLoader2 cl = new URLClassLoader2(new URL[0])) {
+        try (URLClassLoader2 cl = new URLClassLoader2("Test", new URL[0])) {
             assertInjectingJarsWorks(cl);
         }
     }

pom.xml

@@ -87,7 +87,7 @@ THE SOFTWARE.
     <changelog.url>https://www.jenkins.io/changelog</changelog.url>
 
     <!-- Bundled Remoting version -->
-    <remoting.version>3206.vb_15dcf73f6a_9</remoting.version>
+    <remoting.version>3242.vfe5ce6301591</remoting.version>
     <!-- Minimum Remoting version, which is tested for API compatibility -->
     <remoting.minimum.supported.version>4.13</remoting.minimum.supported.version>
 

war/src/main/java/executable/Main.java

@@ -266,7 +266,7 @@ public static void main(String[] args) throws IllegalAccessException {
         // locate the Winstone launcher
         ClassLoader cl;
         try {
-            cl = new URLClassLoader(new URL[] {tmpJar.toURI().toURL()});
+            cl = new URLClassLoader("Jenkins Main ClassLoader", new URL[] {tmpJar.toURI().toURL()}, ClassLoader.getSystemClassLoader());
         } catch (MalformedURLException e) {
             throw new UncheckedIOException(e);
         }