refactor: avoid exception when lambda_handler envs not present in aws-lambda instrumentation (open-telemetry#2750)

Author: Ronald-TR

CHANGELOG.md

@@ -7,8 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
-### Fixed
+## Fixed
 
+- `opentelemetry-instrumentation-aws-lambda` Avoid exception when a handler is not present.
+  ([#2750](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/2750))
 - `opentelemetry-instrumentation-django` Fix regression - `http.target` re-added back to old semconv duration metrics
   ([#2746](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/2746))
 - `opentelemetry-instrumentation-grpc` Fixes the issue with the gRPC instrumentation not working with the 1.63.0 and higher version of gRPC

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

@@ -410,7 +410,7 @@ def _instrument(self, **kwargs):
         """Instruments Lambda Handlers on AWS Lambda.
 
         See more:
-        https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/instrumentation/aws-lambda.md#instrumenting-aws-lambda
+        https://github.com/open-telemetry/semantic-conventions/blob/main/docs/faas/aws-lambda.md
 
         Args:
             **kwargs: Optional arguments
@@ -422,6 +422,14 @@ def _instrument(self, **kwargs):
                     request.
         """
         lambda_handler = os.environ.get(ORIG_HANDLER, os.environ.get(_HANDLER))
+        if not lambda_handler:
+            logger.warning(
+                (
+                    "Could not find the ORIG_HANDLER or _HANDLER in the environment variables. ",
+                    "This instrumentation requires the OpenTelemetry Lambda extension installed.",
+                )
+            )
+            return
         # pylint: disable=attribute-defined-outside-init
         (
             self._wrapped_module_name,

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

@@ -495,6 +495,20 @@ def test_lambda_handles_handler_exception_with_api_gateway_proxy_event(
 
         exc_env_patch.stop()
 
+    def test_lambda_handles_should_do_nothing_when_environment_variables_not_present(
+        self,
+    ):
+        exc_env_patch = mock.patch.dict(
+            "os.environ",
+            {_HANDLER: ""},
+        )
+        exc_env_patch.start()
+        AwsLambdaInstrumentor().instrument()
+
+        spans = self.memory_exporter.get_finished_spans()
+        self.assertEqual(len(spans), 0)
+        exc_env_patch.stop()
+
     def test_uninstrument(self):
         AwsLambdaInstrumentor().instrument()