starlette/fastapi: fix error on host-based routing (#3507)

* starlette/fastapi: fix error on host-based routing

Fix #3506

* Update CHANGELOG.md

* Update instrumentation/opentelemetry-instrumentation-starlette/tests/test_starlette_instrumentation.py

* Update CHANGELOG.md

---------

Co-authored-by: Riccardo Magliocchetti <riccardo.magliocchetti@gmail.com>
Co-authored-by: Emídio Neto <9735060+emdneto@users.noreply.github.com>

CHANGELOG.md

@@ -23,6 +23,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#3679](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3679))
 - `opentelemetry-instrumentation`: Avoid calls to `context.detach` with `None` token.
   ([#3673](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3673))
+- `opentelemetry-instrumentation-starlette`/`opentelemetry-instrumentation-fastapi`: Fixes a crash when host-based routing is used
+  ([#3507](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3507))
 
 ### Added
 

instrumentation/opentelemetry-instrumentation-fastapi/src/opentelemetry/instrumentation/fastapi/__init__.py

@@ -516,7 +516,11 @@ def _get_route_details(scope):
     for starlette_route in app.routes:
         match, _ = starlette_route.matches(scope)
         if match == Match.FULL:
+            try:
                 route = starlette_route.path
+            except AttributeError:
+                # routes added via host routing won't have a path attribute
+                route = scope.get("path")
             break
         if match == Match.PARTIAL:
             route = starlette_route.path

instrumentation/opentelemetry-instrumentation-fastapi/tests/test_fastapi_instrumentation.py

@@ -234,6 +234,7 @@ class TestBaseFastAPI(TestBase):
             raise UnhandledException("This is an unhandled exception")
 
         app.mount("/sub", app=sub_app)
+        app.host("testserver2", sub_app)
 
         return app
 
@@ -310,6 +311,26 @@ class TestBaseManualFastAPI(TestBaseFastAPI):
             span.attributes[HTTP_URL],
         )
 
+    def test_host_fastapi_call(self):
+        client = TestClient(self._app, base_url="https://testserver2")
+        client.get("/")
+        spans = self.memory_exporter.get_finished_spans()
+
+        spans_with_http_attributes = [
+            span
+            for span in spans
+            if (HTTP_URL in span.attributes or HTTP_TARGET in span.attributes)
+        ]
+
+        self.assertEqual(1, len(spans_with_http_attributes))
+
+        for span in spans_with_http_attributes:
+            self.assertEqual("/", span.attributes[HTTP_TARGET])
+            self.assertEqual(
+                "https://testserver2:443/",
+                span.attributes[HTTP_URL],
+            )
+
 
 class TestBaseAutoFastAPI(TestBaseFastAPI):
     @classmethod

instrumentation/opentelemetry-instrumentation-starlette/src/opentelemetry/instrumentation/starlette/__init__.py

@@ -354,7 +354,11 @@ def _get_route_details(scope: dict[str, Any]) -> str | None:
     for starlette_route in app.routes:
         match, _ = starlette_route.matches(scope)
         if match == Match.FULL:
+            try:
                 route = starlette_route.path
+            except AttributeError:
+                # routes added via host routing won't have a path attribute
+                route = scope.get("path")
             break
         if match == Match.PARTIAL:
             route = starlette_route.path

instrumentation/opentelemetry-instrumentation-starlette/tests/test_starlette_instrumentation.py

@@ -18,7 +18,7 @@ from unittest.mock import patch
 
 from starlette import applications
 from starlette.responses import PlainTextResponse
-from starlette.routing import Mount, Route
+from starlette.routing import Host, Mount, Route
 from starlette.testclient import TestClient
 from starlette.websockets import WebSocket
 
@@ -140,6 +140,24 @@ class TestStarletteManualInstrumentation(TestBase):
                 span.attributes[HTTP_URL],
             )
 
+    def test_host_starlette_call(self):
+        client = TestClient(self._app, base_url="http://testserver2")
+        client.get("/home")
+        spans = self.memory_exporter.get_finished_spans()
+
+        spans_with_http_attributes = [
+            span
+            for span in spans
+            if (HTTP_URL in span.attributes or HTTP_TARGET in span.attributes)
+        ]
+
+        for span in spans_with_http_attributes:
+            self.assertEqual("/home", span.attributes[HTTP_TARGET])
+            self.assertEqual(
+                "http://testserver2/home",
+                span.attributes[HTTP_URL],
+            )
+
     def test_starlette_route_attribute_added(self):
         """Ensure that starlette routes are used as the span name."""
         self._client.get("/user/123")
@@ -294,6 +312,7 @@ class TestStarletteManualInstrumentation(TestBase):
                 Route("/user/{username}", home),
                 Route("/healthzz", health),
                 Mount("/sub", app=sub_app),
+                Host("testserver2", sub_app),
             ],
         )