use reflection to read the message size

Author: laurit

instrumentation/grpc-1.6/javaagent/build.gradle.kts

@@ -8,7 +8,6 @@ muzzle {
     module.set("grpc-core")
     versions.set("[1.6.0,)")
     assertInverse.set(true)
-    extraDependency("io.grpc:grpc-protobuf:1.5.0")
   }
 }
 
@@ -22,7 +21,7 @@ dependencies {
   testInstrumentation(project(":instrumentation:netty:netty-4.1:javaagent"))
 
   testLibrary("io.grpc:grpc-netty:$grpcVersion")
-  library("io.grpc:grpc-protobuf:$grpcVersion")
+  testLibrary("io.grpc:grpc-protobuf:$grpcVersion")
   testLibrary("io.grpc:grpc-services:$grpcVersion")
   testLibrary("io.grpc:grpc-stub:$grpcVersion")
 

instrumentation/grpc-1.6/library/build.gradle.kts

@@ -7,9 +7,9 @@ val grpcVersion = "1.6.0"
 
 dependencies {
   library("io.grpc:grpc-core:$grpcVersion")
-  library("io.grpc:grpc-protobuf:$grpcVersion")
 
   testLibrary("io.grpc:grpc-netty:$grpcVersion")
+  testLibrary("io.grpc:grpc-protobuf:$grpcVersion")
   testLibrary("io.grpc:grpc-services:$grpcVersion")
   testLibrary("io.grpc:grpc-stub:$grpcVersion")
 

instrumentation/grpc-1.6/library/src/main/java/io/opentelemetry/instrumentation/grpc/v1_6/BodySizeUtil.java

@@ -5,15 +5,42 @@
 
 package io.opentelemetry.instrumentation.grpc.v1_6;
 
-import com.google.protobuf.MessageLite;
+import java.lang.reflect.Method;
+import javax.annotation.Nullable;
 
 final class BodySizeUtil {
+  @Nullable private static final Class<?> messageLiteClass = getMessageLiteClass();
+
+  @Nullable
+  private static final Method serializedSizeMethod =
+      messageLiteClass != null ? getSerializedSizeMethod(messageLiteClass) : null;
+
+  private static Class<?> getMessageLiteClass() {
+    try {
+      return Class.forName("com.google.protobuf.MessageLite");
+    } catch (Exception ignore) {
+      return null;
+    }
+  }
+
+  private static Method getSerializedSizeMethod(Class<?> clazz) {
+    try {
+      return clazz.getMethod("getSerializedSize");
+    } catch (NoSuchMethodException ignore) {
+      return null;
+    }
+  }
 
   static <T> Long getBodySize(T message) {
-    if (message instanceof MessageLite) {
-      return (long) ((MessageLite) message).getSerializedSize();
-    } else {
-      // Message is not a protobuf message
+    if (messageLiteClass == null || serializedSizeMethod == null) {
+      return null;
+    }
+    if (!messageLiteClass.isInstance(message)) {
+      return null;
+    }
+    try {
+      return ((Integer) serializedSizeMethod.invoke(message)).longValue();
+    } catch (Throwable ignore) {
       return null;
     }
   }