Add Django ASGI support

This diff adds `asgi` as an extra, and uses its methods if the current
request is an `ASGIRequest`.

I still need to dig deeper in the current test suite, to find a way to
duplicate the tests in
`instrumentation/opentelemetry-instrumentation-django/tests/test_middleware.py`,
but using an
[`AsyncClient`](https://docs.djangoproject.com/en/3.1/topics/testing/tools/#testing-asynchronous-code).

Fixes open-telemetry#165, open-telemetry#185, open-telemetry#280, open-telemetry#334.

Author: adamantike

Diff for: instrumentation/opentelemetry-instrumentation-django/setup.cfg

@@ -45,6 +45,8 @@ install_requires =
     opentelemetry-semantic-conventions == 0.24b0
 
 [options.extras_require]
+asgi =
+    opentelemetry-instrumentation-asgi == 0.22.dev0
 test =
     opentelemetry-test == 0.24b0
 

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

@@ -26,7 +26,7 @@
 from opentelemetry.instrumentation.utils import extract_attributes_from_object
 from opentelemetry.instrumentation.wsgi import (
     add_response_attributes,
-    collect_request_attributes,
+    collect_request_attributes as wsgi_collect_request_attributes,
     wsgi_getter,
 )
 from opentelemetry.propagate import extract
@@ -68,6 +68,25 @@ def __call__(self, request):
         MiddlewareMixin = object
 
 
+try:
+    from django.core.handlers.asgi import ASGIRequest
+except ImportError:
+    ASGIRequest = None
+
+try:
+    from opentelemetry.instrumentation.asgi import (
+        asgi_getter,
+        collect_request_attributes as asgi_collect_request_attributes,
+        set_status_code,
+    )
+    _is_asgi_supported = True
+except ImportError:
+    asgi_getter = None
+    asgi_collect_request_attributes = None
+    set_status_code = None
+    _is_asgi_supported = False
+
+
 _logger = getLogger(__name__)
 _attributes_by_preference = [
     [
@@ -132,6 +151,9 @@ def _get_span_name(request):
         except Resolver404:
             return "HTTP {}".format(request.method)
 
+    def _is_asgi_request(self, request):
+        return ASGIRequest and isinstance(request, ASGIRequest)
+
     def process_request(self, request):
         # request.META is a dictionary containing all available HTTP headers
         # Read more about request.META here:
@@ -140,12 +162,23 @@ def process_request(self, request):
         if self._excluded_urls.url_disabled(request.build_absolute_uri("?")):
             return
 
+        is_asgi_request = self._is_asgi_request(request)
+        if is_asgi_request and not _is_asgi_supported:
+            return
+
         # pylint:disable=W0212
         request._otel_start_time = time()
 
         request_meta = request.META
 
-        token = attach(extract(request_meta, getter=wsgi_getter))
+        if is_asgi_request:
+            carrier_getter = asgi_getter
+            collect_request_attributes = asgi_collect_request_attributes
+        else:
+            carrier_getter = wsgi_getter
+            collect_request_attributes = wsgi_collect_request_attributes
+
+        token = attach(extract(request_meta, getter=carrier_getter))
 
         span = self._tracer.start_span(
             self._get_span_name(request),
@@ -207,15 +240,22 @@ def process_response(self, request, response):
         if self._excluded_urls.url_disabled(request.build_absolute_uri("?")):
             return response
 
+        is_asgi_request = self._is_asgi_request(request)
+        if is_asgi_request and not _is_asgi_supported:
+            return
+
         activation = request.META.pop(self._environ_activation_key, None)
         span = request.META.pop(self._environ_span_key, None)
 
         if activation and span:
-            add_response_attributes(
-                span,
-                "{} {}".format(response.status_code, response.reason_phrase),
-                response,
-            )
+            if is_asgi_request:
+                set_status_code(request.META[self._environ_span_key], response.status_code)
+            else:
+                add_response_attributes(
+                    span,
+                    "{} {}".format(response.status_code, response.reason_phrase),
+                    response,
+                )
 
             propagator = get_global_response_propagator()
             if propagator:
@@ -238,7 +278,10 @@ def process_response(self, request, response):
                 activation.__exit__(None, None, None)
 
         if self._environ_token in request.META.keys():
-            detach(request.environ.get(self._environ_token))
+            if is_asgi_request:
+                detach(request.META.get(self._environ_token))
+            else:
+                detach(request.environ.get(self._environ_token))
             request.META.pop(self._environ_token)
 
         return response

Diff for: tox.ini

@@ -238,7 +238,7 @@ commands_pre =
 
   falcon,flask,django,pyramid,tornado,starlette,fastapi,aiohttp,asgi,requests,urllib,wsgi: pip install {toxinidir}/util/opentelemetry-util-http[test]
   wsgi,falcon,flask,django,pyramid: pip install {toxinidir}/instrumentation/opentelemetry-instrumentation-wsgi[test]
-  asgi,starlette,fastapi: pip install {toxinidir}/instrumentation/opentelemetry-instrumentation-asgi[test]
+  asgi,django,starlette,fastapi: pip install {toxinidir}/instrumentation/opentelemetry-instrumentation-asgi[test]
 
   asyncpg: pip install {toxinidir}/instrumentation/opentelemetry-instrumentation-asyncpg[test]