instrumentation/aws-lambda: don't print warnings outside of AWS Lambda (#3183)

If we are not running inside AWS Lambda don't print warnings on missing
OTel lambda extension layer.
The instrumentation is installed by the OTel k8s operator and so this
warning may confuse users.

instrumentation/opentelemetry-instrumentation-aws-lambda/src/opentelemetry/instrumentation/aws_lambda/__init__.py

@@ -431,6 +431,11 @@ class AwsLambdaInstrumentor(BaseInstrumentor):
                     the context is extracted from the HTTP headers of an API Gateway
                     request.
         """
+
+        # Don't try if we are not running on AWS Lambda
+        if "AWS_LAMBDA_FUNCTION_NAME" not in os.environ:
+            return
+
         lambda_handler = os.environ.get(ORIG_HANDLER, os.environ.get(_HANDLER))
         if not lambda_handler:
             logger.warning(

instrumentation/opentelemetry-instrumentation-aws-lambda/tests/test_aws_lambda_instrumentation_manual.py

@@ -11,6 +11,8 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+
+import logging
 import os
 from dataclasses import dataclass
 from importlib import import_module, reload
@@ -124,7 +126,10 @@ class TestAwsLambdaInstrumentorBase(TestBase):
         super().setUp()
         self.common_env_patch = mock.patch.dict(
             "os.environ",
-            {_HANDLER: "tests.mocks.lambda_function.handler"},
+            {
+                _HANDLER: "tests.mocks.lambda_function.handler",
+                "AWS_LAMBDA_FUNCTION_NAME": "mylambda",
+            },
         )
         self.common_env_patch.start()
 
@@ -466,15 +471,40 @@ class TestAwsLambdaInstrumentor(TestAwsLambdaInstrumentorBase):
 
         exc_env_patch.stop()
 
-    def test_lambda_handles_should_do_nothing_when_environment_variables_not_present(
+    @mock.patch("opentelemetry.instrumentation.aws_lambda.logger")
+    def test_lambda_handles_should_do_nothing_when_aws_lambda_environment_variables_not_present(
+        self, logger_mock
+    ):
+        exc_env_patch = mock.patch.dict(
+            "os.environ",
+            {_HANDLER: "tests.mocks.lambda_function.handler"},
+            clear=True,
+        )
+        exc_env_patch.start()
+        AwsLambdaInstrumentor().instrument()
+
+        spans = self.memory_exporter.get_finished_spans()
+        self.assertEqual(len(spans), 0)
+        exc_env_patch.stop()
+
+        logger_mock.warnings.assert_not_called()
+
+    def test_lambda_handles_should_warn_when_handler_environment_variable_not_present(
         self,
     ):
         exc_env_patch = mock.patch.dict(
             "os.environ",
-            {_HANDLER: ""},
+            {"AWS_LAMBDA_FUNCTION_NAME": "mylambda"},
+            clear=True,
         )
         exc_env_patch.start()
+        with self.assertLogs(level=logging.WARNING) as warning:
             AwsLambdaInstrumentor().instrument()
+        self.assertEqual(len(warning.records), 1)
+        self.assertIn(
+            "This instrumentation requires the OpenTelemetry Lambda extension installed",
+            warning.records[0].message,
+        )
 
         spans = self.memory_exporter.get_finished_spans()
         self.assertEqual(len(spans), 0)