Starlette: use route name as transaction name if available

Unfortunately, we need to do some matching here that Starlette does
too, but currently isn't exposed. If/when encode/starlette#804
is merged, we can re-use the route from there.

closes elastic#833

elasticapm/contrib/starlette/__init__.py

@@ -35,6 +35,7 @@
 from starlette.middleware.base import BaseHTTPMiddleware, RequestResponseEndpoint
 from starlette.requests import Request
 from starlette.responses import Response
+from starlette.routing import Match
 from starlette.types import ASGIApp
 
 import elasticapm
@@ -178,7 +179,8 @@ async def _request_started(self, request: Request):
         self.client.begin_transaction("request", trace_parent=trace_parent)
 
         await set_context(lambda: get_data_from_request(request, self.client.config, constants.TRANSACTION), "request")
-        elasticapm.set_transaction_name("{} {}".format(request.method, request.url.path), override=False)
+        transaction_name = self.get_route_name(request) or request.url.path
+        elasticapm.set_transaction_name("{} {}".format(request.method, transaction_name), override=False)
 
     async def _request_finished(self, response: Response):
         """Captures the end of the request processing to APM.
@@ -192,3 +194,15 @@ async def _request_finished(self, response: Response):
 
         result = "HTTP {}xx".format(response.status_code // 100)
         elasticapm.set_transaction_result(result, override=False)
+
+    def get_route_name(self, request: Request) -> str:
+        path = None
+        routes = request.scope["app"].routes
+        for route in routes:
+            match, _ = route.matches(request.scope)
+            if match == Match.FULL:
+                path = route.path
+                break
+            elif match == Match.PARTIAL and path is None:
+                path = route.path
+        return path

tests/contrib/asyncio/starlette_tests.py

@@ -55,6 +55,11 @@ async def hi(request):
             pass
         return PlainTextResponse("ok")
 
+    @app.route("/hi/{name}", methods=["GET"])
+    async def hi_name(request):
+        name = request.path_params["name"]
+        return PlainTextResponse("Hi {}".format(name))
+
     @app.route("/raise-exception", methods=["GET", "POST"])
     async def raise_exception(request):
         raise ValueError()
@@ -210,3 +215,23 @@ def test_capture_headers_body_is_dynamic(app, elasticapm_client):
     assert elasticapm_client.events[constants.TRANSACTION][2]["context"]["request"]["body"] == "[REDACTED]"
     assert "headers" not in elasticapm_client.events[constants.ERROR][1]["context"]["request"]
     assert elasticapm_client.events[constants.ERROR][1]["context"]["request"]["body"] == "[REDACTED]"
+
+
+def test_transaction_name_is_route(app, elasticapm_client):
+    client = TestClient(app)
+
+    response = client.get(
+        "/hi/shay",
+        headers={
+            constants.TRACEPARENT_HEADER_NAME: "00-0af7651916cd43dd8448eb211c80319c-b7ad6b7169203331-03",
+            constants.TRACESTATE_HEADER_NAME: "foo=bar,bar=baz",
+            "REMOTE_ADDR": "127.0.0.1",
+        },
+    )
+
+    assert response.status_code == 200
+
+    assert len(elasticapm_client.events[constants.TRANSACTION]) == 1
+    transaction = elasticapm_client.events[constants.TRANSACTION][0]
+    assert transaction["name"] == "GET /hi/{name}"
+    assert transaction["context"]["request"]["url"]["pathname"] == "/hi/shay"