Remove plugin classloader indirection (#113154)

Extensible plugins use a custom classloader for other plugin jars. When
extensible plugins were first added, the transport client still existed,
and elasticsearch plugins did not exist in the transport client (at
least not the ones that create classloaders). Yet the transport client
still created a PluginsService. An indirection was used to avoid
creating separate classloaders when the transport client had created the
PluginsService.

The transport client was removed in 8.0, but the indirection still
exists. This commit removes that indirection layer.

Author: rjernst

build-tools-internal/src/main/java/org/elasticsearch/gradle/internal/InternalDistributionModuleCheckTaskProvider.java

@@ -59,7 +59,6 @@ public class InternalDistributionModuleCheckTaskProvider {
         "org.elasticsearch.nativeaccess",
         "org.elasticsearch.plugin",
         "org.elasticsearch.plugin.analysis",
-        "org.elasticsearch.pluginclassloader",
         "org.elasticsearch.securesm",
         "org.elasticsearch.server",
         "org.elasticsearch.simdvec",

libs/plugin-classloader/build.gradle

@@ -40,8 +40,6 @@ dependencies {
   api project(":libs:elasticsearch-tdigest")
   implementation project(":libs:elasticsearch-simdvec")
 
-  implementation project(':libs:elasticsearch-plugin-classloader')
-
   // lucene
   api "org.apache.lucene:lucene-core:${versions.lucene}"
   api "org.apache.lucene:lucene-analysis-common:${versions.lucene}"

libs/plugin-classloader/src/main/java/module-info.java

@@ -25,7 +25,6 @@
     requires org.elasticsearch.nativeaccess;
     requires org.elasticsearch.geo;
     requires org.elasticsearch.lz4;
-    requires org.elasticsearch.pluginclassloader;
     requires org.elasticsearch.securesm;
     requires org.elasticsearch.xcontent;
     requires org.elasticsearch.logging;

server/build.gradle

@@ -7,7 +7,7 @@
  * License v3.0 only", or the "Server Side Public License, v 1".
  */
 
-package org.elasticsearch.plugins.loader;
+package org.elasticsearch.plugins;
 
 import java.security.AccessController;
 import java.security.PrivilegedAction;
@@ -17,7 +17,7 @@
 /**
  * A classloader that is a union over the parent core classloader and classloaders of extended plugins.
  */
-public class ExtendedPluginsClassLoader extends ClassLoader {
+class ExtendedPluginsClassLoader extends ClassLoader {
 
     /** Loaders of plugins extended by a plugin. */
     private final List<ClassLoader> extendedLoaders;

server/src/main/java/module-info.java

@@ -468,7 +468,7 @@ private void loadBundle(
             );
         }
 
-        final ClassLoader parentLoader = PluginLoaderIndirection.createLoader(
+        final ClassLoader parentLoader = ExtendedPluginsClassLoader.create(
             getClass().getClassLoader(),
             extendedPlugins.stream().map(LoadedPlugin::loader).toList()
         );

libs/plugin-classloader/src/main/java/org/elasticsearch/plugins/loader/ExtendedPluginsClassLoader.java renamed to server/src/main/java/org/elasticsearch/plugins/ExtendedPluginsClassLoader.java

@@ -53,11 +53,6 @@ grant codeBase "${codebase.lucene-misc}" {
   permission java.nio.file.LinkPermission "hard";
 };
 
-grant codeBase "${codebase.elasticsearch-plugin-classloader}" {
-  // needed to create the classloader which allows plugins to extend other plugins
-  permission java.lang.RuntimePermission "createClassLoader";
-};
-
 grant codeBase "${codebase.elasticsearch-core}" {
   permission java.lang.RuntimePermission "createClassLoader";
   permission java.lang.RuntimePermission "getClassLoader";