Add UserExcludedClassloadersConfigurer (open-telemetry#10134)

Author: anhermon

docs/advanced-configuration-options.md

@@ -18,6 +18,14 @@ which could have unknown side-effects.
 | ------------------------------ | ------------------------------ | -------------------------------------------------------------------------------------------------- |
 | otel.javaagent.exclude-classes | OTEL_JAVAAGENT_EXCLUDE_CLASSES | Suppresses all instrumentation for specific classes, format is "my.package.MyClass,my.package2.\*" |
 
+## Excluding specific classes loaders
+
+This option can be used to exclude classes loaded by given class loaders from being instrumented.
+
+| System property                      | Environment variable                 | Purpose                                                                         |
+|--------------------------------------|--------------------------------------|---------------------------------------------------------------------------------|
+| otel.javaagent.exclude-class-loaders | OTEL_JAVAAGENT_EXCLUDE_CLASS_LOADERS | Ignore the specified class loaders, format is "my.package.MyClass,my.package2." |
+
 ## Running application with security manager
 
 This option can be used to let agent run with all privileges without being affected by security policy restricting some operations.

javaagent-tooling/src/main/java/io/opentelemetry/javaagent/tooling/ignore/UserExcludedClassLoadersConfigurer.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.javaagent.tooling.ignore;
+
+import static java.util.Collections.emptyList;
+
+import com.google.auto.service.AutoService;
+import io.opentelemetry.javaagent.extension.ignore.IgnoredTypesBuilder;
+import io.opentelemetry.javaagent.extension.ignore.IgnoredTypesConfigurer;
+import io.opentelemetry.sdk.autoconfigure.spi.ConfigProperties;
+import java.util.List;
+
+@AutoService(IgnoredTypesConfigurer.class)
+public class UserExcludedClassLoadersConfigurer implements IgnoredTypesConfigurer {
+
+  // visible for tests
+  static final String EXCLUDED_CLASS_LOADERS_CONFIG = "otel.javaagent.exclude-class-loaders";
+
+  @Override
+  public void configure(IgnoredTypesBuilder builder, ConfigProperties config) {
+    List<String> excludedClassLoaders = config.getList(EXCLUDED_CLASS_LOADERS_CONFIG, emptyList());
+    for (String excludedClassLoader : excludedClassLoaders) {
+      excludedClassLoader = excludedClassLoader.trim();
+      // remove the trailing *
+      if (excludedClassLoader.endsWith("*")) {
+        excludedClassLoader = excludedClassLoader.substring(0, excludedClassLoader.length() - 1);
+      }
+      builder.ignoreClassLoader(excludedClassLoader);
+    }
+  }
+}

javaagent-tooling/src/test/java/io/opentelemetry/javaagent/tooling/ignore/UserExcludedClassLoadersConfigurerTest.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.javaagent.tooling.ignore;
+
+import static io.opentelemetry.javaagent.tooling.ignore.UserExcludedClassLoadersConfigurer.EXCLUDED_CLASS_LOADERS_CONFIG;
+import static java.util.Arrays.asList;
+import static java.util.Collections.emptyList;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoInteractions;
+import static org.mockito.Mockito.when;
+
+import io.opentelemetry.javaagent.extension.ignore.IgnoredTypesBuilder;
+import io.opentelemetry.javaagent.extension.ignore.IgnoredTypesConfigurer;
+import io.opentelemetry.sdk.autoconfigure.spi.ConfigProperties;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+@ExtendWith(MockitoExtension.class)
+class UserExcludedClassLoadersConfigurerTest {
+
+  @Mock ConfigProperties config;
+  @Mock IgnoredTypesBuilder builder;
+
+  IgnoredTypesConfigurer underTest = new UserExcludedClassLoadersConfigurer();
+
+  @Test
+  void shouldAddNothingToBuilderWhenPropertyIsEmpty() {
+    // when
+    underTest.configure(builder, config);
+
+    // then
+    verifyNoInteractions(builder);
+  }
+
+  @Test
+  void shouldIgnoreClassesAndPackages() {
+    // given
+    when(config.getList(EXCLUDED_CLASS_LOADERS_CONFIG, emptyList()))
+        .thenReturn(
+            asList("com.example.IgnoredClass", "com.example.ignored.*", "com.another_ignore"));
+
+    // when
+    underTest.configure(builder, config);
+
+    // then
+    verify(builder).ignoreClassLoader("com.example.IgnoredClass");
+    verify(builder).ignoreClassLoader("com.example.ignored.");
+    verify(builder).ignoreClassLoader("com.another_ignore");
+  }
+}