Add monitoring for anonymous user ID code paths (#26176)

For ARCHBOM-1674 we need more information on how often save=False is
actually used vs. other code paths.

common/djangoapps/student/models.py

@@ -43,6 +43,7 @@ from django.utils.translation import ugettext_lazy as _
 from django.utils.translation import ugettext_noop
 from django_countries.fields import CountryField
 from edx_django_utils.cache import RequestCache
+from edx_django_utils import monitoring
 from edx_rest_api_client.exceptions import SlumberBaseException
 from eventtracking import tracker
 from model_utils.models import TimeStampedModel
@@ -162,8 +163,15 @@ def anonymous_id_for_user(user, course_id, save=True):
     if user.is_anonymous:
         return None
 
+    # ARCHBOM-1674: Get a sense of what fraction of anonymous_user_id calls are
+    # cached, stored in the DB, or retrieved from the DB. This will help inform
+    # us on decisions about whether we can move to always save IDs,
+    # pregenerate them, use random instead of deterministic IDs, etc.
+    monitoring.increment('temp_anonymous_user_id.requested')
+
     cached_id = getattr(user, '_anonymous_id', {}).get(course_id)
     if cached_id is not None:
+        monitoring.increment('temp_anonymous_user_id.returned_from_cache')
         return cached_id
 
     # include the secret key as a salt, and to make the ids unique across different LMS installs.
@@ -180,6 +188,7 @@ def anonymous_id_for_user(user, course_id, save=True):
     user._anonymous_id[course_id] = digest  # pylint: disable=protected-access
 
     if save is False:
+        monitoring.increment('temp_anonymous_user_id.computed_unsaved')
         return digest
 
     try:
@@ -188,10 +197,11 @@ def anonymous_id_for_user(user, course_id, save=True):
             course_id=course_id,
             anonymous_user_id=digest,
         )
+        monitoring.increment('temp_anonymous_user_id.computed_stored')
     except IntegrityError:
         # Another thread has already created this entry, so
         # continue
-        pass
+        monitoring.increment('temp_anonymous_user_id.computed_already_present')
 
     return digest