[django] the tracer can be disabled using a Django settings; by default it's the opposite of DEBUG

Author: Emanuele Palazzetti

ddtrace/contrib/django/apps.py

@@ -23,19 +23,20 @@ def ready(self):
         Tracing capabilities must be enabled in this function so that
         all Django internals are properly configured.
         """
-        tracer = settings.DEFAULT_TRACER
-
-        # define the service details
-        tracer.set_service_info(
-            service=settings.DEFAULT_SERVICE,
-            app='django',
-            app_type=AppTypes.web,
-        )
-
-        try:
-            # trace Django internals
-            patch_template(tracer)
-            patch_db(tracer)
-        except Exception:
-            # TODO[manu]: we can provide better details there
-            log.exception('error patching Django internals')
+        if settings.ENABLED:
+            tracer = settings.DEFAULT_TRACER
+
+            # define the service details
+            tracer.set_service_info(
+                service=settings.DEFAULT_SERVICE,
+                app='django',
+                app_type=AppTypes.web,
+            )
+
+            try:
+                # trace Django internals
+                patch_template(tracer)
+                patch_db(tracer)
+            except Exception:
+                # TODO[manu]: we can provide better details there
+                log.exception('error patching Django internals')

ddtrace/contrib/django/conf.py

@@ -25,6 +25,7 @@
 DEFAULTS = {
     'DEFAULT_TRACER': 'ddtrace.tracer',
     'DEFAULT_SERVICE': 'django',
+    'ENABLED': not django_settings.DEBUG,
 }
 
 # List of settings that may be in string import notation.

ddtrace/contrib/django/middleware.py

@@ -8,6 +8,7 @@
 
 # 3p
 from django.apps import apps
+from django.core.exceptions import MiddlewareNotUsed
 
 
 log = logging.getLogger(__name__)
@@ -17,6 +18,11 @@ class TraceMiddleware(object):
     """
     Middleware that traces Django requests
     """
+    def __init__(self):
+        # disable the middleware if the tracer is not enabled
+        if not settings.ENABLED:
+            raise MiddlewareNotUsed
+
     def process_request(self, request):
         tracer = settings.DEFAULT_TRACER
 

tests/contrib/django/app/settings.py

@@ -67,4 +67,5 @@
 DATADOG_APM = {
     # tracer with a DummyWriter
     'DEFAULT_TRACER': 'tests.contrib.django.utils.tracer',
+    'ENABLED': True,
 }