Configurable Middleware Position for Django Instrumentation (#2912)

Author: saichander17

CHANGELOG.md

@@ -417,6 +417,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#1879](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1879))
 - Add optional distro and configurator selection for auto-instrumentation
   ([#1823](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1823))
+- `opentelemetry-instrumentation-django` - Add option to add Opentelemetry middleware at specific position in middleware chain
+  ([#2912]https://github.com/open-telemetry/opentelemetry-python-contrib/pull/2912)
 
 ### Added
 

instrumentation/opentelemetry-instrumentation-django/src/opentelemetry/instrumentation/django/__init__.py

@@ -285,6 +285,30 @@ def _get_django_middleware_setting() -> str:
     return "MIDDLEWARE"
 
 
+def _get_django_otel_middleware_position(
+    middleware_length, default_middleware_position=0
+):
+    otel_position = environ.get("OTEL_PYTHON_DJANGO_MIDDLEWARE_POSITION")
+    try:
+        middleware_position = int(otel_position)
+    except (ValueError, TypeError):
+        _logger.debug(
+            "Invalid OTEL_PYTHON_DJANGO_MIDDLEWARE_POSITION value: (%s). Using default position: %d.",
+            otel_position,
+            default_middleware_position,
+        )
+        middleware_position = default_middleware_position
+
+    if middleware_position < 0 or middleware_position > middleware_length:
+        _logger.debug(
+            "Middleware position %d is out of range (0-%d). Using 0 as the position",
+            middleware_position,
+            middleware_length,
+        )
+        middleware_position = 0
+    return middleware_position
+
+
 class DjangoInstrumentor(BaseInstrumentor):
     """An instrumentor for Django
 
@@ -388,10 +412,18 @@ def _instrument(self, **kwargs):
 
         is_sql_commentor_enabled = kwargs.pop("is_sql_commentor_enabled", None)
 
+        middleware_position = _get_django_otel_middleware_position(
+            len(settings_middleware), kwargs.pop("middleware_position", 0)
+        )
+
         if is_sql_commentor_enabled:
-            settings_middleware.insert(0, self._sql_commenter_middleware)
+            settings_middleware.insert(
+                middleware_position, self._sql_commenter_middleware
+            )
 
-        settings_middleware.insert(0, self._opentelemetry_middleware)
+        settings_middleware.insert(
+            middleware_position, self._opentelemetry_middleware
+        )
 
         setattr(settings, _middleware_setting, settings_middleware)
 

instrumentation/opentelemetry-instrumentation-django/tests/test_middleware.py

@@ -157,6 +157,46 @@ def tearDownClass(cls):
         super().tearDownClass()
         conf.settings = conf.LazySettings()
 
+    def test_middleware_added_at_position(self):
+        _django_instrumentor.uninstrument()
+        if DJANGO_2_0:
+            middleware = conf.settings.MIDDLEWARE
+        else:
+            middleware = conf.settings.MIDDLEWARE_CLASSES
+        # adding two dummy middlewares
+        temprory_middelware = "django.utils.deprecation.MiddlewareMixin"
+        middleware.append(temprory_middelware)
+        middleware.append(temprory_middelware)
+
+        middleware_position = 1
+        _django_instrumentor.instrument(
+            middleware_position=middleware_position
+        )
+        self.assertEqual(
+            middleware[middleware_position],
+            "opentelemetry.instrumentation.django.middleware.otel_middleware._DjangoMiddleware",
+        )
+
+    def test_middleware_added_at_position_if_wrong_position(self):
+        _django_instrumentor.uninstrument()
+        if DJANGO_2_0:
+            middleware = conf.settings.MIDDLEWARE
+        else:
+            middleware = conf.settings.MIDDLEWARE_CLASSES
+        # adding middleware
+        temprory_middelware = "django.utils.deprecation.MiddlewareMixin"
+        middleware.append(temprory_middelware)
+        middleware_position = (
+            756  # wrong position out of bound of middleware length
+        )
+        _django_instrumentor.instrument(
+            middleware_position=middleware_position
+        )
+        self.assertEqual(
+            middleware[0],
+            "opentelemetry.instrumentation.django.middleware.otel_middleware._DjangoMiddleware",
+        )
+
     def test_templated_route_get(self):
         Client().get("/route/2020/template/")
 

instrumentation/opentelemetry-instrumentation-django/tests/test_sqlcommenter.py

@@ -72,6 +72,37 @@ def test_middleware_added(self, sqlcommenter_middleware):
             in middleware
         )
 
+    @patch(
+        "opentelemetry.instrumentation.django.middleware.sqlcommenter_middleware.SqlCommenter"
+    )
+    def test_middleware_added_at_position(self, sqlcommenter_middleware):
+        _django_instrumentor.uninstrument()
+        if DJANGO_2_0:
+            middleware = conf.settings.MIDDLEWARE
+        else:
+            middleware = conf.settings.MIDDLEWARE_CLASSES
+
+        # adding two dummy middlewares
+        temprory_middelware = "django.utils.deprecation.MiddlewareMixin"
+        middleware.append(temprory_middelware)
+        middleware.append(temprory_middelware)
+
+        middleware_position = 1
+        _django_instrumentor.instrument(
+            is_sql_commentor_enabled=True,
+            middleware_position=middleware_position,
+        )
+        instance = sqlcommenter_middleware.return_value
+        instance.get_response = HttpResponse()
+        self.assertEqual(
+            middleware[middleware_position],
+            "opentelemetry.instrumentation.django.middleware.otel_middleware._DjangoMiddleware",
+        )
+        self.assertEqual(
+            middleware[middleware_position + 1],
+            "opentelemetry.instrumentation.django.middleware.sqlcommenter_middleware.SqlCommenter",
+        )
+
     @patch(
         "opentelemetry.instrumentation.django.middleware.sqlcommenter_middleware._get_opentelemetry_values"
     )