fix: Recognize OTEL_EXPORTER_OTLP_ENDPOINT as custom endpoint in Lambda environment

aws-opentelemetry-distro/src/amazon/opentelemetry/distro/aws_opentelemetry_configurator.py

@@ -92,6 +92,7 @@
 AWS_XRAY_DAEMON_ADDRESS_CONFIG = "AWS_XRAY_DAEMON_ADDRESS"
 OTEL_AWS_PYTHON_DEFER_TO_WORKERS_ENABLED_CONFIG = "OTEL_AWS_PYTHON_DEFER_TO_WORKERS_ENABLED"
 SYSTEM_METRICS_INSTRUMENTATION_SCOPE_NAME = "opentelemetry.instrumentation.system_metrics"
+OTEL_EXPORTER_OTLP_ENDPOINT = "OTEL_EXPORTER_OTLP_ENDPOINT"
 OTEL_EXPORTER_OTLP_TRACES_ENDPOINT = "OTEL_EXPORTER_OTLP_TRACES_ENDPOINT"
 OTEL_EXPORTER_OTLP_LOGS_ENDPOINT = "OTEL_EXPORTER_OTLP_LOGS_ENDPOINT"
 OTEL_EXPORTER_OTLP_LOGS_HEADERS = "OTEL_EXPORTER_OTLP_LOGS_HEADERS"
@@ -406,7 +407,8 @@ def _customize_span_exporter(span_exporter: SpanExporter, resource: Resource) ->
     traces_endpoint = os.environ.get(OTEL_EXPORTER_OTLP_TRACES_ENDPOINT)
     if _is_lambda_environment():
         # Override OTLP http default endpoint to UDP
-        if isinstance(span_exporter, OTLPSpanExporter) and traces_endpoint is None:
+        # Check for custom endpoint using both signal-specific and generic env vars per OTel spec
+        if isinstance(span_exporter, OTLPSpanExporter) and not _has_custom_otlp_traces_endpoint():
             traces_endpoint = os.environ.get(AWS_XRAY_DAEMON_ADDRESS_CONFIG, "127.0.0.1:2000")
             span_exporter = OTLPUdpSpanExporter(endpoint=traces_endpoint)
 
@@ -645,6 +647,18 @@ def _is_lambda_environment():
     return AWS_LAMBDA_FUNCTION_NAME_CONFIG in os.environ
 
 
+def _has_custom_otlp_traces_endpoint():
+    """Check if a custom OTLP traces endpoint is configured.
+
+    Per OpenTelemetry OTLP Exporter specification, check for signal-specific
+    endpoint first, then fall back to generic endpoint.
+    """
+    return (
+        os.environ.get(OTEL_EXPORTER_OTLP_TRACES_ENDPOINT) is not None
+        or os.environ.get(OTEL_EXPORTER_OTLP_ENDPOINT) is not None
+    )
+
+
 def _is_aws_otlp_endpoint(otlp_endpoint: Optional[str], service: str) -> bool:
     """Is the given endpoint an AWS OTLP endpoint?"""
 

aws-opentelemetry-distro/tests/amazon/opentelemetry/distro/test_aws_opentelementry_configurator.py

@@ -19,6 +19,7 @@
 from amazon.opentelemetry.distro.aws_opentelemetry_configurator import (
     LAMBDA_SPAN_EXPORT_BATCH_SIZE,
     OTEL_AWS_ENHANCED_CODE_ATTRIBUTES,
+    OTEL_EXPORTER_OTLP_ENDPOINT,
     OTEL_EXPORTER_OTLP_LOGS_ENDPOINT,
     OTEL_EXPORTER_OTLP_LOGS_HEADERS,
     OTEL_EXPORTER_OTLP_TRACES_ENDPOINT,
@@ -40,6 +41,7 @@
     _export_unsampled_span_for_agent_observability,
     _export_unsampled_span_for_lambda,
     _fetch_logs_header,
+    _has_custom_otlp_traces_endpoint,
     _init_logging,
     _is_application_signals_enabled,
     _is_application_signals_runtime_enabled,
@@ -388,6 +390,37 @@ def test_customize_span_exporter_with_agent_observability(self):
         os.environ.pop("AGENT_OBSERVABILITY_ENABLED", None)
         os.environ.pop(OTEL_EXPORTER_OTLP_TRACES_ENDPOINT, None)
 
+    def test_customize_span_exporter_lambda_with_generic_otlp_endpoint(self):
+        """Test that setting OTEL_EXPORTER_OTLP_ENDPOINT in Lambda uses OTLP exporter, not UDP.
+
+        Per OpenTelemetry OTLP Exporter specification, the generic endpoint should be
+        recognized as a custom endpoint and prevent fallback to UDP export.
+        Fixes: https://github.com/aws-observability/aws-otel-js-instrumentation/issues/297
+        """
+        # Set Lambda environment and generic OTLP endpoint (not signal-specific)
+        os.environ["AWS_LAMBDA_FUNCTION_NAME"] = "myLambdaFunc"
+        os.environ[OTEL_EXPORTER_OTLP_ENDPOINT] = "http://my-collector:4318"
+
+        try:
+            mock_exporter = MagicMock(spec=OTLPSpanExporter)
+            customized_exporter = _customize_span_exporter(mock_exporter, Resource.get_empty())
+
+            # Should NOT be converted to UDP - the generic endpoint should be respected
+            self.assertNotIsInstance(customized_exporter, OTLPUdpSpanExporter)
+            # Should remain as the original exporter (not wrapped since App Signals not enabled)
+            self.assertEqual(mock_exporter, customized_exporter)
+
+            # Also verify the helper function works correctly
+            self.assertTrue(_has_custom_otlp_traces_endpoint())
+        finally:
+            os.environ.pop("AWS_LAMBDA_FUNCTION_NAME", None)
+            os.environ.pop(OTEL_EXPORTER_OTLP_ENDPOINT, None)
+
+        # Verify helper returns False when no endpoints are set
+        os.environ.pop(OTEL_EXPORTER_OTLP_TRACES_ENDPOINT, None)
+        os.environ.pop(OTEL_EXPORTER_OTLP_ENDPOINT, None)
+        self.assertFalse(_has_custom_otlp_traces_endpoint())
+
     def test_customize_span_processors_with_agent_observability(self):
         mock_tracer_provider: TracerProvider = MagicMock()