fix instrumentation module not loading silently when duplicate helper classnames are detected.

issue #9752 introduced a check that prevents an instrumentation module from being loaded when duplicate helper classes are detected. Such a case may arise when a class is detected by muzzle as a helper class and at the same time it is registered in additionalHelperClasses. Before #9752, the module would properly load.

The proposed change will allow the instrumentation to load and log a warning. While it may be true that this is actually an issue in the instrumentation module, such cases are not obvious to find, there are modules in the field that have stopped working because this change and the fix should not lead to unintended behavior as we can expect the bytecode of the duplicates to be identical.

Author: FlorianBruckner

muzzle/src/main/java/io/opentelemetry/javaagent/tooling/HelperInjector.java

@@ -7,6 +7,7 @@
 
 import static java.util.logging.Level.FINE;
 import static java.util.logging.Level.SEVERE;
+import static java.util.logging.Level.WARNING;
 
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import io.opentelemetry.instrumentation.api.internal.cache.Cache;
@@ -183,8 +184,11 @@ public DynamicType.Builder<?> transform(
                           HelperClassDefinition::getClassName,
                           helper -> () -> helper.getBytecode().getBytecode(),
                           (a, b) -> {
-                            throw new IllegalStateException(
-                                "Duplicate classnames for helper class detected!");
+                            logger.log(
+                                WARNING,
+                                "Duplicate classname for helper class in module {0} detected",
+                                new Object[] {this.requestingName});
+                            return a;
                           },
                           LinkedHashMap::new));