django: Fix carrier usage on ASGI requests (#767)

* django: Fix carrier usage on ASGI requests

For ASGI requests, we must use `request.scope` instead of
`request.META`. This is because `ASGIGetter` retrieves the `headers` key
from the carrier [0], which is only present in `request.scope`.

[0] https://github.com/open-telemetry/opentelemetry-python-contrib/blob/main/instrumentation/opentelemetry-instrumentation-asgi/src/opentelemetry/instrumentation/asgi/__init__.py#L133

* Add unit tests

Author: adamantike

Diff for: CHANGELOG.md

@@ -15,6 +15,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#766](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/766))
 - `opentelemetry-instrumentation-falcon` Dropped broken support for Python 3.4.
   ([#774](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/774))
+- `opentelemetry-instrumentation-django` Fixed carrier usage on ASGI requests.
+  ([#767](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/767))
 
 ## [1.6.2-0.25b2](https://github.com/open-telemetry/opentelemetry-python/releases/tag/v1.6.2-0.25b2) - 2021-10-19
 

Diff for: instrumentation/opentelemetry-instrumentation-django/src/opentelemetry/instrumentation/django/middleware.py

@@ -184,7 +184,7 @@ def process_request(self, request):
             carrier_getter = wsgi_getter
             collect_request_attributes = wsgi_collect_request_attributes
 
-        token = attach(extract(request_meta, getter=carrier_getter))
+        token = attach(extract(carrier, getter=carrier_getter))
 
         span = self._tracer.start_span(
             self._get_span_name(request),

Diff for: instrumentation/opentelemetry-instrumentation-django/tests/test_middleware.py

@@ -31,10 +31,16 @@
 )
 from opentelemetry.sdk import resources
 from opentelemetry.sdk.trace import Span
+from opentelemetry.sdk.trace.id_generator import RandomIdGenerator
 from opentelemetry.semconv.trace import SpanAttributes
 from opentelemetry.test.test_base import TestBase
 from opentelemetry.test.wsgitestutil import WsgiTestBase
-from opentelemetry.trace import SpanKind, StatusCode
+from opentelemetry.trace import (
+    SpanKind,
+    StatusCode,
+    format_span_id,
+    format_trace_id,
+)
 from opentelemetry.util.http import get_excluded_urls, get_traced_request_attrs
 
 # pylint: disable=import-error
@@ -331,6 +337,29 @@ def response_hook(span, request, response):
         self.assertIsInstance(response_hook_args[2], HttpResponse)
         self.assertEqual(response_hook_args[2], response)
 
+    async def test_trace_parent(self):
+        id_generator = RandomIdGenerator()
+        trace_id = format_trace_id(id_generator.generate_trace_id())
+        span_id = format_span_id(id_generator.generate_span_id())
+        traceparent_value = f"00-{trace_id}-{span_id}-01"
+
+        Client().get(
+            "/span_name/1234/", traceparent=traceparent_value,
+        )
+        span = self.memory_exporter.get_finished_spans()[0]
+
+        self.assertEqual(
+            trace_id, format_trace_id(span.get_span_context().trace_id),
+        )
+        self.assertIsNotNone(span.parent)
+        self.assertEqual(
+            trace_id, format_trace_id(span.parent.trace_id),
+        )
+        self.assertEqual(
+            span_id, format_span_id(span.parent.span_id),
+        )
+        self.memory_exporter.clear()
+
     def test_trace_response_headers(self):
         response = Client().get("/span_name/1234/")
 

Diff for: instrumentation/opentelemetry-instrumentation-django/tests/test_middleware_asgi.py

@@ -32,6 +32,7 @@
 )
 from opentelemetry.sdk import resources
 from opentelemetry.sdk.trace import Span
+from opentelemetry.sdk.trace.id_generator import RandomIdGenerator
 from opentelemetry.semconv.trace import SpanAttributes
 from opentelemetry.test.test_base import TestBase
 from opentelemetry.trace import (
@@ -317,6 +318,29 @@ def response_hook(span, request, response):
         self.assertIsInstance(response_hook_args[2], HttpResponse)
         self.assertEqual(response_hook_args[2], response)
 
+    async def test_trace_parent(self):
+        id_generator = RandomIdGenerator()
+        trace_id = format_trace_id(id_generator.generate_trace_id())
+        span_id = format_span_id(id_generator.generate_span_id())
+        traceparent_value = f"00-{trace_id}-{span_id}-01"
+
+        await self.async_client.get(
+            "/span_name/1234/", traceparent=traceparent_value,
+        )
+        span = self.memory_exporter.get_finished_spans()[0]
+
+        self.assertEqual(
+            trace_id, format_trace_id(span.get_span_context().trace_id),
+        )
+        self.assertIsNotNone(span.parent)
+        self.assertEqual(
+            trace_id, format_trace_id(span.parent.trace_id),
+        )
+        self.assertEqual(
+            span_id, format_span_id(span.parent.span_id),
+        )
+        self.memory_exporter.clear()
+
     async def test_trace_response_headers(self):
         response = await self.async_client.get("/span_name/1234/")