Use dictionary for ASGI scope storage (backport #2726) (#2755)

* Use dictionary for ASGI scope storage (#2726)

(cherry picked from commit 41ae8b4)

# Conflicts:
#	ddtrace/contrib/asgi/middleware.py
#	releasenotes/notes/asgi-span-19e772cb2f09ef4d.yaml

* fix format

Co-authored-by: Kyle Verhoog <[email protected]>
Co-authored-by: Tahir H. Butt <[email protected]>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

Author: 3 people

ddtrace/contrib/asgi/__init__.py

@@ -30,6 +30,18 @@ def custom_handle_exception_span(exc, span):
     app = TraceMiddleware(app, handle_exception_span=custom_handle_exception_span)
 
 
+To retrieve the request span from the scope of an ASGI request use the ``span_from_scope``
+function::
+
+    from ddtrace.contrib.asgi import span_from_scope
+
+    def handle_request(scope, send):
+        span = span_from_scope(scope)
+        if span:
+            span.set_tag(...)
+        ...
+
+
 Configuration
 ~~~~~~~~~~~~~
 

ddtrace/contrib/asgi/middleware.py

@@ -70,7 +70,7 @@ def _default_handle_exception_span(exc, span):
 def span_from_scope(scope):
     # type: (Mapping[str, Any]) -> Optional[Span]
     """Retrieve the top-level ASGI span from the scope."""
-    return scope.get("datadog_span")
+    return scope.get("datadog", {}).get("request_span")
 
 
 class TraceMiddleware:
@@ -119,7 +119,7 @@ async def __call__(self, scope, receive, send):
             span_type=SpanTypes.WEB,
         )
 
-        scope["datadog_span"] = span
+        scope["datadog"] = {"request_span": span}
 
         if self.span_modifier:
             self.span_modifier(span, scope)
@@ -177,4 +177,8 @@ async def wrapped_send(message):
             self.handle_exception_span(exc, span)
             reraise(exc_type, exc_val, exc_tb)
         finally:
+            try:
+                del scope["datadog"]["request_span"]
+            except KeyError:
+                pass
             span.finish()

releasenotes/notes/asgi-span-19e772cb2f09ef4d.yaml

@@ -1,6 +1,5 @@
 ---
 features:
   - |
-    ASGI: store the ASGI span in the scope. The span is stored under the
-      ``"datadog_span"`` key and can be retrieved using the
+    ASGI: store the ASGI span in the scope. The span can be retrieved with the
       ``ddtrace.contrib.asgi.span_from_scope`` function.