Bootstrap lookup fix

CHANGELOG.asciidoc

@@ -48,6 +48,7 @@ endif::[]
 ===== Bug fixes
 * Fix `HttpUrlConnection` instrumentation issue (affecting distributed tracing as well) when using HTTPS without using
  `java.net.HttpURLConnection#disconnect` - {pull}1447[1447]
+* Fixes class loading issue that can occur when deploying multiple applications to the same application server - {pull}1458[#1458]
 
 [[release-notes-1.x]]
 === Java Agent version 1.x

apm-agent-core/src/main/java/co/elastic/apm/agent/bci/IndyBootstrap.java

@@ -26,6 +26,7 @@
 
 import co.elastic.apm.agent.bci.classloading.ExternalPluginClassLoader;
 import co.elastic.apm.agent.bci.classloading.IndyPluginClassLoader;
+import co.elastic.apm.agent.bci.classloading.LookupExposer;
 import co.elastic.apm.agent.sdk.state.GlobalState;
 import co.elastic.apm.agent.util.JvmRuntimeInfo;
 import co.elastic.apm.agent.util.PackageScanner;
@@ -43,6 +44,7 @@
 import java.lang.invoke.MethodType;
 import java.lang.reflect.Method;
 import java.net.URISyntaxException;
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.ConcurrentHashMap;
@@ -272,12 +274,13 @@ public static ConstantCallSite bootstrap(MethodHandles.Lookup lookup,
  MethodHandle instrumentedMethod = args.length >= 5 ? (MethodHandle) args[4] : null;
 
  ClassLoader adviceClassLoader = ElasticApmAgent.getClassLoader(adviceClassName);
- List<String> pluginClasses;
+ List<String> pluginClasses = new ArrayList<>();
  if (adviceClassLoader instanceof ExternalPluginClassLoader) {
- pluginClasses = ((ExternalPluginClassLoader) adviceClassLoader).getClassNames();
+ pluginClasses.addAll(((ExternalPluginClassLoader) adviceClassLoader).getClassNames());
  } else {
- pluginClasses = getClassNamesFromBundledPlugin(adviceClassName, adviceClassLoader);
+ pluginClasses.addAll(getClassNamesFromBundledPlugin(adviceClassName, adviceClassLoader));
  }
+ pluginClasses.add(LookupExposer.class.getName());
  ClassLoader pluginClassLoader = IndyPluginClassLoaderFactory.getOrCreatePluginClassLoader(
  lookup.lookupClass().getClassLoader(),
  pluginClasses,
@@ -287,7 +290,10 @@ public static ConstantCallSite bootstrap(MethodHandles.Lookup lookup,
  // also, this plugin is used as a dependency in other plugins
  .or(nameStartsWith("co.elastic.apm.agent.concurrent")));
  Class<?> adviceInPluginCL = pluginClassLoader.loadClass(adviceClassName);
- MethodHandle methodHandle = MethodHandles.lookup().findStatic(adviceInPluginCL, adviceMethodName, adviceMethodType);
+ Class<LookupExposer> lookupExposer = (Class<LookupExposer>) pluginClassLoader.loadClass(LookupExposer.class.getName());
+ // can't use MethodHandle.lookup(), see also https://github.com/elastic/apm-agent-java/issues/1450
+ MethodHandles.Lookup indyLookup = (MethodHandles.Lookup) lookupExposer.getMethod("getLookup").invoke(null);
+ MethodHandle methodHandle = indyLookup.findStatic(adviceInPluginCL, adviceMethodName, adviceMethodType);
  return new ConstantCallSite(methodHandle);
  } catch (Exception e) {
  // must not be a static field as it would initialize logging before it's ready

apm-agent-core/src/main/java/co/elastic/apm/agent/bci/classloading/LookupExposer.java

@@ -0,0 +1,42 @@
+/*-
+ * #%L
+ * Elastic APM Java agent
+ * %%
+ * Copyright (C) 2018 - 2020 Elastic and contributors
+ * %%
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ * #L%
+ */
+package co.elastic.apm.agent.bci.classloading;
+
+import java.lang.invoke.MethodHandles;
+
+/**
+ * This class is injected into every {@link IndyPluginClassLoader} in {@link co.elastic.apm.agent.bci.IndyBootstrap#bootstrap}
+ * so that the bootstrap can use a {@link MethodHandles.Lookup} with a lookup class from within the {@link IndyPluginClassLoader},
+ * instead of calling {@link MethodHandles#lookup()} which uses the caller class as the lookup class.
+ * <p>
+ * This circumvents a nasty JVM bug that's described <a href="https://github.com/elastic/apm-agent-java/issues/1450">here</a>.
+ * </p>
+ */
+public class LookupExposer {
+
+ public static MethodHandles.Lookup getLookup() {
+ return MethodHandles.lookup();
+ }
+}