fix(django): include the view class name in resource names (backport #5891 to 1.13) (#5906)

Resolves: #5711

## Checklist

- [x] Change(s) are motivated and described in the PR description.
- [x] Testing strategy is described if automated tests are not included
in the PR.
- [x] Risk is outlined (performance impact, potential for breakage,
maintainability, etc).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] [Library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/contributing.html#Release-Note-Guidelines)
are followed.
- [x] Documentation is included (in-code, generated user docs, [public
corp docs](https://github.com/DataDog/documentation/)).
- [x] OPTIONAL: PR description includes explicit acknowledgement of the
performance implications of the change as reported in the benchmarks PR
comment.

## Reviewer Checklist

- [x] Title is accurate.
- [x] No unnecessary changes are introduced.
- [x] Description motivates each change.
- [x] Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes unless absolutely necessary.
- [x] Testing strategy adequately addresses listed risk(s).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] Release note makes sense to a user of the library.
- [x] Reviewer has explicitly acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment.

Author: mabdinur

ddtrace/contrib/django/utils.py

@@ -188,7 +188,13 @@ def _set_resolver_tags(pin, span, request):
             # The request quite likely failed (e.g. 404) so we do the resolution anyway.
             resolver = get_resolver(getattr(request, "urlconf", None))
             resolver_match = resolver.resolve(request.path_info)
-        handler = func_name(resolver_match[0])
+
+        if hasattr(resolver_match[0], "view_class"):
+            # In django==4.0, view.__name__ defaults to <module>.views.view
+            # Accessing view.view_class is equired for django>4.0 to get the name of underlying view
+            handler = func_name(resolver_match[0].view_class)
+        else:
+            handler = func_name(resolver_match[0])
 
         route = None
         # In Django >= 2.2.0 we can access the original route or regex pattern

releasenotes/notes/django-fix-view-names-55a357e1ac903ea5.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    django: Resolves an issue where the resource name of django.request span did not contain the full name of a view
+    when ``DD_DJANGO_USE_HANDLER_RESOURCE_FORMAT=True``. This issue impacts ``django>=4.0``.

tests/contrib/django/test_django.py

@@ -492,6 +492,30 @@ def test_request_view(client, test_spans):
     )
 
 
+def test_class_views_resource_names(client, test_spans):
+    """
+    When making a request to a Django app and DD_DJANGO_USE_HANDLER_RESOURCE_FORMAT=True
+        The resource name of the django.request span should contain the name of the view
+    """
+    with override_config("django", dict(use_handler_resource_format=True)):
+        # Send a request to a endpoint with a class based view
+        resp = client.get("/simple/")
+        assert resp.status_code == 200
+        assert resp.content == b""
+
+    view_spans = list(test_spans.filter_spans(name="django.view"))
+    assert len(view_spans) == 1
+    # Assert span properties
+    view_span = view_spans[0]
+    view_span.assert_matches(
+        name="django.view", service="django", resource="tests.contrib.django.views.BasicView", error=0
+    )
+    # Get request span
+    request_span = list(test_spans.filter_spans(name="django.request"))[0]
+    # Ensure resource name contains the view
+    assert view_span.resource in request_span.resource
+
+
 def test_lambda_based_view(client, test_spans):
     # ensures that the internals are properly traced when using a function view
     assert client.get("/lambda-view/").status_code == 200

tests/contrib/django/test_django_snapshots.py

@@ -291,3 +291,12 @@ def test_templates_disabled():
         resp = client.get("/template-view/")
         assert resp.status_code == 200
         assert resp.content == b"some content\n"
+
+
+@snapshot(ignores=["meta.http.useragent"])
+@pytest.mark.skipif(django.VERSION < (3, 0, 0), reason="ASGI not supported in django<3")
+def test_django_resource_handler():
+    # regression test for: DataDog/dd-trace-py/issues/5711
+    with daphne_client("application", additional_env={"DD_DJANGO_USE_HANDLER_RESOURCE_FORMAT": "true"}) as client:
+        # Request a class based view
+        assert client.get("simple/").status_code == 200