chore(django): remove django.process_exception event/handler (#14293)

We can remove the need for `with ctx.span` and calling an additional
`django.process_exception` event by adding support for
`should_set_traceback` to the `_finish_span` trace handler.

This will help to further remove span references/usage in the django
integration.


## Checklist
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- The PR description articulates the motivation for the change
- The change includes tests OR the PR description describes a testing
strategy
- The PR description notes risks associated with the change, if any
- Newly-added code is easy to change
- The change follows the [library release note
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- The change includes or references documentation updates if necessary
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[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist
- [ ] Reviewer has checked that all the criteria below are met 
- Title is accurate
- All changes are related to the pull request's stated goal
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[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes
- Testing strategy adequately addresses listed risks
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implications of this PR as reported in the benchmarks PR comment
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Author: brettlangdon

ddtrace/_trace/trace_handlers.py

@@ -161,6 +161,8 @@ def _finish_span(
     exc_type, exc_value, exc_traceback = exc_info
     if exc_type and exc_value and exc_traceback:
         span.set_exc_info(exc_type, exc_value, exc_traceback)
+    elif ctx.get_item("should_set_traceback", False):
+        span.set_traceback()
     span.finish()
 
 
@@ -546,11 +548,6 @@ def _on_django_func_wrapped(_unused1, _unused2, _unused3, ctx, ignored_excs):
             ctx.span._ignore_exception(exc)
 
 
-def _on_django_process_exception(ctx: core.ExecutionContext, should_set_traceback: bool):
-    if should_set_traceback:
-        ctx.span.set_traceback()
-
-
 def _on_django_block_request(ctx: core.ExecutionContext, metadata: Dict[str, str], django_config, url: str, query: str):
     for tk, tv in metadata.items():
         ctx.span.set_tag_str(tk, tv)
@@ -890,7 +887,6 @@ def listen():
     core.on("django.start_response", _on_django_start_response)
     core.on("django.cache", _on_django_cache)
     core.on("django.func.wrapped", _on_django_func_wrapped)
-    core.on("django.process_exception", _on_django_process_exception)
     core.on("django.block_request_callback", _on_django_block_request)
     core.on("django.after_request_headers.post", _on_django_after_request_headers_post)
     core.on("botocore.patched_api_call.exception", _on_botocore_patched_api_call_exception)
@@ -989,7 +985,7 @@ def listen():
     ):
         core.on(f"context.started.{context_name}", _start_span)
 
-    for name in ("django.template.render",):
+    for name in ("django.template.render", "django.process_exception"):
         core.on(f"context.ended.{name}", _finish_span)
 
 

ddtrace/contrib/internal/django/patch.py

@@ -360,11 +360,11 @@ def wrapped(django, pin, func, instance, args, kwargs):
         tags = {COMPONENT: config_django.integration_name}
         with core.context_with_data(
             "django.process_exception", span_name=name, resource=resource, tags=tags, pin=pin
-        ) as ctx, ctx.span:
+        ) as ctx:
             resp = func(*args, **kwargs)
-            core.dispatch(
-                "django.process_exception", (ctx, hasattr(resp, "status_code") and 500 <= resp.status_code < 600)
-            )
+
+            # Tell finish span that we should collect the traceback
+            ctx.set_item("should_set_traceback", hasattr(resp, "status_code") and 500 <= resp.status_code < 600)
             return resp
 
     return trace_utils.with_traced_module(wrapped)(django)