address code review feedback. Cache the return from getMethod("getFunctionArn").

Author: lukeina2z

instrumentation/aws-sdk/aws-sdk-1.11/library/src/main/java/io/opentelemetry/instrumentation/awssdk/v1_11/RequestAccess.java

@@ -8,13 +8,12 @@
 import java.lang.invoke.MethodHandle;
 import java.lang.invoke.MethodHandles;
 import java.lang.invoke.MethodType;
-import java.lang.reflect.Method;
 import javax.annotation.Nullable;
 
 final class RequestAccess {
+  private static final String LAMBDA_REQUEST_CLASS_PREFIX = "com.amazonaws.services.lambda.model.";
   private static final String SECRETS_MANAGER_REQUEST_CLASS_PREFIX =
       "com.amazonaws.services.secretsmanager.model.";
-  private static final String LAMBDA_REQUEST_CLASS_PREFIX = "com.amazonaws.services.lambda.model.";
   private static final String STEP_FUNCTIONS_REQUEST_CLASS_PREFIX =
       "com.amazonaws.services.stepfunctions.model.";
 
@@ -34,11 +33,7 @@ static String getLambdaArn(Object request) {
     }
     try {
       Object config = access.getLambdaConfiguration.invoke(request);
-      if (config == null) {
-        return null;
-      }
-      Method method = config.getClass().getMethod("getFunctionArn");
-      return (String) method.invoke(config);
+      return invokeOrNull(access.getLambdaArnFromConfiguration, config);
     } catch (Throwable t) {
       return null;
     }
@@ -130,6 +125,7 @@ private static String invokeOrNull(@Nullable MethodHandle method, Object obj) {
 
   @Nullable private final MethodHandle getBucketName;
   @Nullable private final MethodHandle getLambdaConfiguration;
+  @Nullable private final MethodHandle getLambdaArnFromConfiguration;
   @Nullable private final MethodHandle getLambdaName;
   @Nullable private final MethodHandle getLambdaResourceMappingId;
   @Nullable private final MethodHandle getQueueUrl;
@@ -153,6 +149,8 @@ private RequestAccess(Class<?> clz) {
 
     boolean isLambda = clz.getName().startsWith(LAMBDA_REQUEST_CLASS_PREFIX);
     getLambdaConfiguration = isLambda ? findLambdaGetConfigurationMethod(clz) : null;
+    getLambdaArnFromConfiguration =
+        getLambdaConfiguration != null ? findGetLambdaArnMethod() : null;
     getLambdaName = isLambda ? findAccessorOrNull(clz, "getFunctionName") : null;
     getLambdaResourceMappingId = isLambda ? findAccessorOrNull(clz, "getUUID") : null;
     boolean isSecretsManager = clz.getName().startsWith(SECRETS_MANAGER_REQUEST_CLASS_PREFIX);
@@ -188,4 +186,15 @@ private static MethodHandle findLambdaGetConfigurationMethod(Class<?> clz) {
       return null;
     }
   }
+
+  @Nullable
+  private static MethodHandle findGetLambdaArnMethod() {
+    try {
+      Class<?> lambdaConfigurationClass =
+          Class.forName("com.amazonaws.services.lambda.model.FunctionConfiguration");
+      return findAccessorOrNull(lambdaConfigurationClass, "getFunctionArn");
+    } catch (Throwable t) {
+      return null;
+    }
+  }
 }