fix(django): Fix multiple fn middleware sharing the same resource name (#2884) (#2886)

* fix(django): Fix multiple fn middleware sharing the same resource name
Fixes #2873

* fix flake8 issues

* fix other tests

* scope test to >=2.0.0

(cherry picked from commit 83a775a)

Co-authored-by: Brett Langdon <[email protected]>

Author: mergify[bot]

ddtrace/contrib/django/patch.py

@@ -252,19 +252,28 @@ def traced_load_middleware(django, pin, func, instance, args, kwargs):
             base = ".".join(split[:-1])
             attr = split[-1]
 
-            # Function-based middleware is a factory which returns a handler function for requests.
-            # So instead of tracing the factory, we want to trace its returned value.
-            # We wrap the factory to return a traced version of the handler function.
-            def wrapped_factory(func, instance, args, kwargs):
-                # r is the middleware handler function returned from the factory
-                r = func(*args, **kwargs)
-                if r:
-                    return wrapt.FunctionWrapper(r, traced_func(django, "django.middleware", resource=mw_path))
-                # If r is an empty middleware function (i.e. returns None), don't wrap since NoneType cannot be called
-                else:
-                    return r
-
-            trace_utils.wrap(base, attr, wrapped_factory)
+            # DEV: We need to have a closure over `mw_path` for the resource name or else
+            # all function based middleware will share the same resource name
+            def _wrapper(resource):
+                # Function-based middleware is a factory which returns a handler function for requests.
+                # So instead of tracing the factory, we want to trace its returned value.
+                # We wrap the factory to return a traced version of the handler function.
+                def wrapped_factory(func, instance, args, kwargs):
+                    # r is the middleware handler function returned from the factory
+                    r = func(*args, **kwargs)
+                    if r:
+                        return wrapt.FunctionWrapper(
+                            r,
+                            traced_func(django, "django.middleware", resource=resource),
+                        )
+                    # If r is an empty middleware function (i.e. returns None), don't wrap since
+                    # NoneType cannot be called
+                    else:
+                        return r
+
+                return wrapped_factory
+
+            trace_utils.wrap(base, attr, _wrapper(resource=mw_path))
 
         # Instrument class-based middleware
         elif isclass(mw):

releasenotes/notes/django-multiple-function-middleware-54999c787cf003a0.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    Fixes an issue where all Django function middleware will share the same resource name.

tests/contrib/django/middleware.py

@@ -42,6 +42,16 @@ def mw(request):
     return mw
 
 
+def fn2_middleware(get_response):
+    """Function factory middleware."""
+
+    def mw(request):
+        response = get_response(request)
+        return response
+
+    return mw
+
+
 def empty_middleware(get_response):
     """Empty function middleware for regression testing."""
 

tests/contrib/django/test_django.py

@@ -278,7 +278,7 @@ def test_v2XX_middleware(client, test_spans):
         "django.middleware.security.SecurityMiddleware.process_request",
         "django.middleware.security.SecurityMiddleware.process_response",
         "tests.contrib.django.middleware.ClsMiddleware.__call__",
-        "tests.contrib.django.middleware.EverythingMiddleware",
+        "tests.contrib.django.middleware.fn_middleware",
         "tests.contrib.django.middleware.EverythingMiddleware.__call__",
         "tests.contrib.django.middleware.EverythingMiddleware.process_view",
     }
@@ -449,6 +449,15 @@ def test_empty_middleware_func_is_raised_in_django(client, test_spans):
             client.get("/")
 
 
+@pytest.mark.skipif(django.VERSION < (2, 0, 0), reason="")
+def test_multiple_fn_middleware_resource_names(client, test_spans):
+    with modify_settings(MIDDLEWARE={"append": "tests.contrib.django.middleware.fn2_middleware"}):
+        client.get("/")
+
+    assert test_spans.find_span(name="django.middleware", resource="tests.contrib.django.middleware.fn_middleware")
+    assert test_spans.find_span(name="django.middleware", resource="tests.contrib.django.middleware.fn2_middleware")
+
+
 """
 View tests
 """

tests/snapshots/tests.contrib.django.test_django_snapshots.test_404_exceptions.snap

@@ -150,7 +150,7 @@
                                    "duration" 1007000}
                                       {"name" "django.middleware"
                                        "service" "django"
-                                       "resource" "tests.contrib.django.middleware.EverythingMiddleware"
+                                       "resource" "tests.contrib.django.middleware.fn_middleware"
                                        "error" 0
                                        "span_id" 21
                                        "trace_id" 0

tests/snapshots/tests.contrib.django.test_django_snapshots.test_404_exceptions_21x.snap

@@ -149,7 +149,7 @@
                                    "duration" 1023000}
                                       {"name" "django.middleware"
                                        "service" "django"
-                                       "resource" "tests.contrib.django.middleware.EverythingMiddleware"
+                                       "resource" "tests.contrib.django.middleware.fn_middleware"
                                        "error" 0
                                        "span_id" 21
                                        "trace_id" 0

tests/snapshots/tests.contrib.django.test_django_snapshots.test_asgi_200_30.snap

@@ -150,7 +150,7 @@
                                    "duration" 239310}
                                       {"name" "django.middleware"
                                        "service" "django"
-                                       "resource" "tests.contrib.django.middleware.EverythingMiddleware"
+                                       "resource" "tests.contrib.django.middleware.fn_middleware"
                                        "error" 0
                                        "span_id" 21
                                        "trace_id" 0

tests/snapshots/tests.contrib.django.test_django_snapshots.test_asgi_200_31.snap

@@ -152,7 +152,7 @@
                                    "duration" 1720934}
                                       {"name" "django.middleware"
                                        "service" "django"
-                                       "resource" "tests.contrib.django.middleware.EverythingMiddleware"
+                                       "resource" "tests.contrib.django.middleware.fn_middleware"
                                        "error" 0
                                        "span_id" 21
                                        "trace_id" 0

tests/snapshots/tests.contrib.django.test_django_snapshots.test_asgi_200_3x.snap

@@ -152,7 +152,7 @@
                                    "duration" 2065900}
                                       {"name" "django.middleware"
                                        "service" "django"
-                                       "resource" "tests.contrib.django.middleware.EverythingMiddleware"
+                                       "resource" "tests.contrib.django.middleware.fn_middleware"
                                        "error" 0
                                        "span_id" 21
                                        "trace_id" 0

tests/snapshots/tests.contrib.django.test_django_snapshots.test_asgi_500_30.snap

@@ -150,7 +150,7 @@
                                    "duration" 1747119558}
                                       {"name" "django.middleware"
                                        "service" "django"
-                                       "resource" "tests.contrib.django.middleware.EverythingMiddleware"
+                                       "resource" "tests.contrib.django.middleware.fn_middleware"
                                        "error" 0
                                        "span_id" 21
                                        "trace_id" 0