Fix ImportError with slash-delimited Lambda handler paths (#3894)

* Fix ImportError with slash-delimited Lambda handler paths

AWS Lambda accepts handler paths in both formats:
- Slash-delimited: python/functions/api.handler
- Dot-delimited: python.functions.api.handler

The instrumentation was failing when slash-delimited paths were used
because it attempted to import invalid Python module paths containing
forward slashes. This fix normalizes the handler path by converting
slashes to dots before splitting the module and function names.

Fixes #1465

* Add changelog and unit test for slash-delimited handler fix

- Add changelog entry in Unreleased section
- Add unit test verifying both slash and dot-delimited handler paths work
- Test confirms instrumentation handles both formats correctly

Related to #1465

* Update CHANGELOG.md

Co-authored-by: Tammy Baylis <[email protected]>

---------

Co-authored-by: Emídio Neto <[email protected]>
Co-authored-by: Tammy Baylis <[email protected]>
Co-authored-by: Riccardo Magliocchetti <[email protected]>

Author: 4 people

CHANGELOG.md

@@ -24,6 +24,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - `opentelemetry-instrumentation-botocore`: Handle dict input in _decode_tool_use for Bedrock streaming
   ([#3875](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3875))
+- `opentelemetry-instrumentation-aws-lambda`: Fix ImportError with slash-delimited handler paths
+  ([#3894](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3894))
 
 ## Version 1.38.0/0.59b0 (2025-10-16)
 

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

@@ -460,6 +460,8 @@ def _instrument(self, **kwargs):
             )
             return
         # pylint: disable=attribute-defined-outside-init
+        # Convert slash-delimited paths to dot-delimited for valid Python imports
+        lambda_handler = lambda_handler.replace("/", ".")
         (
             self._wrapped_module_name,
             self._wrapped_function_name,

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

@@ -727,6 +727,53 @@ def test_sqs_event_sets_attributes(self):
             MOCK_LAMBDA_CONTEXT_ATTRIBUTES,
         )
 
+    def test_slash_delimited_handler_path(self):
+        """Test that slash-delimited handler paths work correctly.
+
+        AWS Lambda accepts both slash-delimited (python/functions/api.handler)
+        and dot-delimited (python.functions.api.handler) handler paths.
+        This test ensures the instrumentation handles both formats.
+        """
+        # Test slash-delimited format
+        slash_env_patch = mock.patch.dict(
+            "os.environ",
+            {_HANDLER: "tests/mocks/lambda_function.handler"},
+        )
+        slash_env_patch.start()
+        AwsLambdaInstrumentor().instrument()
+
+        mock_execute_lambda()
+
+        spans = self.memory_exporter.get_finished_spans()
+        self.assertEqual(len(spans), 1)
+        self.assertSpanHasAttributes(
+            spans[0],
+            MOCK_LAMBDA_CONTEXT_ATTRIBUTES,
+        )
+
+        slash_env_patch.stop()
+        AwsLambdaInstrumentor().uninstrument()
+        self.memory_exporter.clear()
+
+        # Test dot-delimited format (should still work)
+        dot_env_patch = mock.patch.dict(
+            "os.environ",
+            {_HANDLER: "tests.mocks.lambda_function.handler"},
+        )
+        dot_env_patch.start()
+        AwsLambdaInstrumentor().instrument()
+
+        mock_execute_lambda()
+
+        spans = self.memory_exporter.get_finished_spans()
+        self.assertEqual(len(spans), 1)
+        self.assertSpanHasAttributes(
+            spans[0],
+            MOCK_LAMBDA_CONTEXT_ATTRIBUTES,
+        )
+
+        dot_env_patch.stop()
+
     def test_lambda_handles_handler_exception_with_api_gateway_proxy_event(
         self,
     ):