When loading exporter factories via SPI from an external jar, look only inside that jar, and not any parent classloader. (#569)

agent-tooling/src/main/java/io/opentelemetry/auto/tooling/ExporterClassLoader.java

@@ -68,7 +68,9 @@ public class ExporterClassLoader extends URLClassLoader {
     // A small hack to prevent other exporters from being loaded by this classloader if they
     // should happen to appear on the classpath.
     if (name.equals(
-        "META-INF/services/io.opentelemetry.sdk.contrib.auto.config.SpanExporterFactory")) {
+            "META-INF/services/io.opentelemetry.sdk.contrib.auto.config.SpanExporterFactory")
+        || name.equals(
+            "META-INF/services/io.opentelemetry.sdk.contrib.auto.config.MetricExporterFactory")) {
       return findResources(name);
     }
     return super.getResources(name);

agent-tooling/src/test/groovy/io/opentelemetry/auto/tooling/ExporterClassLoaderTest.groovy

@@ -0,0 +1,144 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ *
+ * Licensed 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.
+ */
+package io.opentelemetry.auto.tooling
+
+
+import io.opentelemetry.sdk.contrib.auto.config.Config
+import io.opentelemetry.sdk.contrib.auto.config.MetricExporterFactory
+import io.opentelemetry.sdk.contrib.auto.config.SpanExporterFactory
+import io.opentelemetry.sdk.metrics.export.MetricExporter
+import io.opentelemetry.sdk.trace.export.SpanExporter
+import java.nio.charset.StandardCharsets
+import java.util.jar.JarEntry
+import java.util.jar.JarOutputStream
+import spock.lang.Specification
+
+class ExporterClassLoaderTest extends Specification {
+
+  // Verifies https://github.com/open-telemetry/opentelemetry-java-instrumentation/issues/542
+  def "does not look in parent classloader for metric exporters"() {
+    setup:
+    def parentClassloader = new URLClassLoader([createJarWithClasses(MetricExporterFactoryParent)] as URL[])
+    def childClassloader = new ExporterClassLoader(createJarWithClasses(MetricExporterFactoryChild), parentClassloader)
+
+    when:
+    ServiceLoader<MetricExporterFactory> serviceLoader = ServiceLoader.load(MetricExporterFactory, childClassloader)
+
+    then:
+    serviceLoader.size() == 1
+  }
+
+  def "does not look in parent classloader for span exporters"() {
+    setup:
+    def parentClassloader = new URLClassLoader([createJarWithClasses(SpanExporterFactoryParent)] as URL[])
+    def childClassloader = new ExporterClassLoader(createJarWithClasses(SpanExporterFactoryChild), parentClassloader)
+
+    when:
+    ServiceLoader<SpanExporterFactory> serviceLoader = ServiceLoader.load(SpanExporterFactory, childClassloader)
+
+    then:
+    serviceLoader.size() == 1
+  }
+
+  static class MetricExporterFactoryParent implements MetricExporterFactory {
+
+    @Override
+    MetricExporter fromConfig(Config config) {
+      return null
+    }
+  }
+
+  static class MetricExporterFactoryChild implements MetricExporterFactory {
+
+    @Override
+    MetricExporter fromConfig(Config config) {
+      return null
+    }
+  }
+
+  static class SpanExporterFactoryParent implements SpanExporterFactory {
+
+    @Override
+    SpanExporter fromConfig(Config config) {
+      return null
+    }
+  }
+
+  static class SpanExporterFactoryChild implements SpanExporterFactory {
+
+    @Override
+    SpanExporter fromConfig(Config config) {
+      return null
+    }
+  }
+
+  static URL createJarWithClasses(final Class<?>... classes)
+    throws IOException {
+    final File tmpJar = File.createTempFile(UUID.randomUUID().toString() + "-", ".jar")
+    tmpJar.deleteOnExit()
+
+    final JarOutputStream target = new JarOutputStream(new FileOutputStream(tmpJar))
+    for (final Class<?> clazz : classes) {
+      addToJar(clazz, clazz.getInterfaces()[0], target)
+    }
+    target.close()
+
+    return tmpJar.toURI().toURL()
+  }
+
+  //This is mostly copy-pasted from IntegrationTestUtils, but we need to save service files as well
+  private static void addToJar(final Class<?> clazz, final Class<?> serviceInterface, final JarOutputStream jarOutputStream)
+    throws IOException {
+    String resourceName = getResourceName(clazz.getName())
+
+    ClassLoader loader = clazz.getClassLoader()
+    if (null == loader) {
+      // bootstrap resources can be fetched through the system loader
+      loader = ClassLoader.getSystemClassLoader()
+    }
+
+    InputStream inputStream = null
+    try {
+      final JarEntry entry = new JarEntry(resourceName)
+      jarOutputStream.putNextEntry(entry)
+      inputStream = loader.getResourceAsStream(resourceName)
+
+      final byte[] buffer = new byte[1024]
+      while (true) {
+        final int count = inputStream.read(buffer)
+        if (count == -1) {
+          break
+        }
+        jarOutputStream.write(buffer, 0, count)
+      }
+      jarOutputStream.closeEntry()
+
+      final JarEntry serviceEntry = new JarEntry("META-INF/services/" + serviceInterface.getName())
+      jarOutputStream.putNextEntry(serviceEntry)
+      jarOutputStream.write(clazz.getName().getBytes(StandardCharsets.UTF_8))
+      jarOutputStream.closeEntry()
+    } finally {
+      if (inputStream != null) {
+        inputStream.close()
+      }
+    }
+  }
+
+  /** com.foo.Bar -> com/foo/Bar.class */
+  private static String getResourceName(final String className) {
+    return className.replace('.', '/') + ".class"
+  }
+}