fix(django): populate span.resource on forced exit [backport 1.16] (#6695)

Backport 94c0415 from #6674 to 1.16.

This change fixes a behavior where span.resource would not be correctly
filled out when django.core.base.handler.BaseHandler.get_response was
terminated. In particular, this issue arose with gunicorn terminating
the active worker after a request took more than the worker timeout
period (default 10 seconds).

Before change:
```
    span.resource = "GET"
```

After Change:
```
    span.resource = "GET <ENDPOINT>"
```

This change also adds a .gitignore entry for an auto-generated file.

## 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/releasenotes.html)
are followed. If no release note is required, add label
`changelog/no-changelog`.
- [x] Documentation is included (in-code, generated user docs, [public
corp docs](https://github.com/DataDog/documentation/)).
- [x] Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## 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.
- [x] Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)

Co-authored-by: Teague Bick <[email protected]>

Author: github-actions[bot]

.gitignore

@@ -14,6 +14,7 @@ ddtrace/profiling/collector/stack.c
 ddtrace/profiling/exporter/pprof.c
 ddtrace/profiling/_build.c
 ddtrace/internal/datadog/profiling/ddup.cpp
+ddtrace/internal/datadog/profiling/_ddup.cpp
 ddtrace/internal/_encoding.c
 ddtrace/internal/_rand.c
 ddtrace/internal/_tagset.c

ddtrace/contrib/django/utils.py

@@ -329,6 +329,9 @@ def _after_request_tags(pin, span, request, response):
             except Exception:
                 log.debug("Error retrieving authentication information for user", exc_info=True)
 
+        # DEV: Resolve the view and resource name at the end of the request in case
+        #      urlconf changes at any point during the request
+        _set_resolver_tags(pin, span, request)
         if response:
             status = response.status_code
             span.set_tag_str("django.response.class", func_name(response))
@@ -361,10 +364,6 @@ def _after_request_tags(pin, span, request, response):
 
             url = get_request_uri(request)
 
-            # DEV: Resolve the view and resource name at the end of the request in case
-            #      urlconf changes at any point during the request
-            _set_resolver_tags(pin, span, request)
-
             request_headers = None
             if config._appsec_enabled:
                 from ddtrace.appsec import _asm_request_context

releasenotes/notes/fix-django-span-resource-on-unexpected-terminate-fbc5ce27d503d635.yaml

@@ -0,0 +1,4 @@
+fixes:
+  - |
+    django: This fix resolves an issue where 'span.resource' would not include the endpoint when a Handler was interrupted, such as in the case
+    of gunicorn worker timeouts.  

tests/contrib/django/test_django.py

@@ -23,7 +23,9 @@
 from ddtrace.constants import ERROR_TYPE
 from ddtrace.constants import SAMPLING_PRIORITY_KEY
 from ddtrace.constants import USER_KEEP
+from ddtrace.contrib import trace_utils
 from ddtrace.contrib.django.patch import instrument_view
+from ddtrace.contrib.django.patch import traced_get_response
 from ddtrace.contrib.django.utils import get_request_uri
 from ddtrace.ext import http
 from ddtrace.ext import user
@@ -2394,3 +2396,22 @@ def test_django_get_user(client, test_spans):
     assert root.get_tag(user.NAME) == "usr.name"
     assert root.get_tag(user.ROLE) == "usr.role"
     assert root.get_tag(user.SCOPE) == "usr.scope"
+
+
+@pytest.mark.skipif(django.VERSION < (2, 0, 0), reason="")
+def test_django_base_handler_failure(client, test_spans):
+    """
+    This tests the failure mode seen with Gunicorn during timeouts, where the Django
+    Handler is terminated after <x> seconds and no response is returned by
+    django.core.handler.base.BaseHandler.get_response.  We expect to populate the resource
+    with "GET <resource>" instead of what we did before this test "GET"
+    """
+    trace_utils.unwrap(client.handler, "get_response")
+    with mock.patch.object(client.handler, "get_response", side_effect=Exception("test")):
+        trace_utils.wrap(client.handler, "get_response", traced_get_response(django))
+        try:
+            client.get("/")
+        except Exception:
+            pass  # We expect an error
+        root = test_spans.get_root_span()
+        assert root.resource == "GET ^$"