Pass request attributes to Sampler in Django (#1730)

Author: rafa-munoz

CHANGELOG.md

@@ -19,6 +19,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#1645](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1645))
 - Add `excluded_urls` functionality to `urllib` and `urllib3` instrumentations
   ([#1733](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1733))
+- Make Django request span attributes available for `start_span`. 
+  ([#1730](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1730))
 
 ### Fixed
 

instrumentation/opentelemetry-instrumentation-django/src/opentelemetry/instrumentation/django/middleware/otel_middleware.py

@@ -212,6 +212,7 @@ def process_request(self, request):
             carrier_getter = wsgi_getter
             collect_request_attributes = wsgi_collect_request_attributes
 
+        attributes = collect_request_attributes(carrier)
         span, token = _start_internal_or_server_span(
             tracer=self._tracer,
             span_name=self._get_span_name(request),
@@ -220,9 +221,9 @@ def process_request(self, request):
             ),
             context_carrier=carrier,
             context_getter=carrier_getter,
+            attributes=attributes,
         )
 
-        attributes = collect_request_attributes(carrier)
         active_requests_count_attrs = _parse_active_request_count_attrs(
             attributes
         )