Add OTEL_AWS_APPLICATION_SIGNALS_ENABLED check for Lambda EMF dimensions

Only add Service and Environment dimensions when both:
- Running in Lambda environment (is_lambda=True)
- Application Signals is enabled (OTEL_AWS_APPLICATION_SIGNALS_ENABLED=true)

This aligns the EMF dimension behavior with the Application Signals feature flag.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: syed-ahsan-ishtiaque

aws-opentelemetry-distro/src/amazon/opentelemetry/distro/exporter/aws/metrics/base_emf_exporter.py

@@ -6,6 +6,7 @@
 import json
 import logging
 import math
+import os
 import time
 from abc import ABC, abstractmethod
 from collections import defaultdict
@@ -206,6 +207,17 @@ def _add_lambda_dimensions(self, emf_log: Dict, dimension_names: List[str], reso
         if not self._is_lambda:
             return dimension_names
 
+        # Only add dimensions when Application Signals is enabled
+        app_signals_enabled = (
+            os.environ.get(
+                "OTEL_AWS_APPLICATION_SIGNALS_ENABLED",
+                os.environ.get("OTEL_AWS_APP_SIGNALS_ENABLED", "false"),
+            ).lower()
+            == "true"
+        )
+        if not app_signals_enabled:
+            return dimension_names
+
         service_name, _ = get_service_attribute(resource) if resource else ("UnknownService", True)
         # Add dimension values to the EMF log root
         emf_log["Service"] = service_name

aws-opentelemetry-distro/tests/amazon/opentelemetry/distro/exporter/aws/metrics/test_base_emf_exporter.py

@@ -1,8 +1,9 @@
 # Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 # SPDX-License-Identifier: Apache-2.0
 
+import os
 import unittest
-from unittest.mock import Mock
+from unittest.mock import Mock, patch
 
 from amazon.opentelemetry.distro.exporter.aws.metrics.base_emf_exporter import BaseEmfExporter, MetricRecord
 from opentelemetry.sdk.metrics.export import MetricExportResult
@@ -300,6 +301,7 @@ def test_is_lambda_initialization(self):
         exporter = ConcreteEmfExporter(is_lambda=True)
         self.assertTrue(exporter._is_lambda)
 
+    @patch.dict(os.environ, {"OTEL_AWS_APPLICATION_SIGNALS_ENABLED": "true"})
     def test_create_emf_log_with_lambda_dimensions(self):
         """Test EMF log creation includes Service and Environment dimensions in Lambda mode."""
         # Create Lambda exporter
@@ -357,6 +359,7 @@ def test_create_emf_log_without_lambda_dimensions(self):
         self.assertNotIn("Service", dimensions)
         self.assertNotIn("Environment", dimensions)
 
+    @patch.dict(os.environ, {"OTEL_AWS_APPLICATION_SIGNALS_ENABLED": "true"})
     def test_create_emf_log_lambda_with_unknown_service(self):
         """Test EMF log creation uses UnknownService when service.name is not set in Lambda mode."""
         lambda_exporter = ConcreteEmfExporter(namespace="TestNamespace", is_lambda=True)
@@ -376,6 +379,7 @@ def test_create_emf_log_lambda_with_unknown_service(self):
         self.assertEqual(result["Service"], "UnknownService")
         self.assertEqual(result["Environment"], "lambda:default")
 
+    @patch.dict(os.environ, {"OTEL_AWS_APPLICATION_SIGNALS_ENABLED": "true"})
     def test_create_emf_log_lambda_with_none_resource(self):
         """Test EMF log creation handles None resource in Lambda mode."""
         lambda_exporter = ConcreteEmfExporter(namespace="TestNamespace", is_lambda=True)
@@ -393,6 +397,52 @@ def test_create_emf_log_lambda_with_none_resource(self):
         self.assertEqual(result["Service"], "UnknownService")
         self.assertEqual(result["Environment"], "lambda:default")
 
+    def test_create_emf_log_lambda_without_application_signals_enabled(self):
+        """Test EMF log does NOT include Service/Environment when is_lambda=True but app signals disabled."""
+        # Create Lambda exporter but without OTEL_AWS_APPLICATION_SIGNALS_ENABLED
+        lambda_exporter = ConcreteEmfExporter(namespace="TestNamespace", is_lambda=True)
+
+        record = lambda_exporter._create_metric_record("test_metric", "Count", "Test")
+        record.value = 50.0
+        record.timestamp = 1234567890
+        record.attributes = {"env": "test"}
+
+        records = [record]
+        resource = Resource.create({"service.name": "my-lambda-service"})
+
+        result = lambda_exporter._create_emf_log(records, resource, 1234567890)
+
+        # Service and Environment should NOT be added when app signals is disabled
+        self.assertNotIn("Service", result)
+        self.assertNotIn("Environment", result)
+
+        # Check that dimensions do NOT include Service and Environment
+        cw_metrics = result["_aws"]["CloudWatchMetrics"][0]
+        dimensions = cw_metrics["Dimensions"][0]
+        self.assertNotIn("Service", dimensions)
+        self.assertNotIn("Environment", dimensions)
+
+    @patch.dict(os.environ, {"OTEL_AWS_APP_SIGNALS_ENABLED": "true"})
+    def test_create_emf_log_lambda_with_deprecated_app_signals_env_var(self):
+        """Test EMF log includes dimensions when using deprecated OTEL_AWS_APP_SIGNALS_ENABLED."""
+        lambda_exporter = ConcreteEmfExporter(namespace="TestNamespace", is_lambda=True)
+
+        record = lambda_exporter._create_metric_record("test_metric", "Count", "Test")
+        record.value = 50.0
+        record.timestamp = 1234567890
+        record.attributes = {}
+
+        records = [record]
+        resource = Resource.create({"service.name": "my-service"})
+
+        result = lambda_exporter._create_emf_log(records, resource, 1234567890)
+
+        # Should add dimensions with deprecated env var
+        self.assertIn("Service", result)
+        self.assertEqual(result["Service"], "my-service")
+        self.assertIn("Environment", result)
+        self.assertEqual(result["Environment"], "lambda:default")
+
 
 if __name__ == "__main__":
     unittest.main()