metrics: Add users in queue

marietje/metrics/views.py

@@ -1,17 +1,30 @@
-from prometheus_client import generate_latest, Gauge
-
-from django.db.models import Q
+from django.db.models import Count, Q
 from django.http import HttpResponse
+from prometheus_client import generate_latest, Gauge
 
 from queues.models import Queue, PlaylistSong
 
 # Export queue length
-g = Gauge('marietje_queue_length', 'Marietje queue length', ['name'])
+queue_length_gauge = Gauge('marietje_queue_length', 'Marietje queue length', ['name'])
 for queue in Queue.objects.all():
     def _get_queue_length():
-         return PlaylistSong.objects.filter(Q(playlist=queue.playlist_id),
-                                           Q(state=0) | Q(state=1)).count()
-    g.labels(name=queue).set_function(_get_queue_length)
+        return (PlaylistSong.objects
+            .filter(Q(playlist=queue.playlist_id), Q(state=0) | Q(state=1))
+            .count())
+    queue_length_gauge.labels(name=queue).set_function(_get_queue_length)
+
+# Export the amount of different users in the queue
+queue_users_gauge = Gauge('marietje_queue_users', 'Users holding a queue at some point', ['name'])
+for queue in Queue.objects.all():
+    def _get_queue_distinct_users():
+        # Ideally, we would use .distinct() here, but it is not supported on
+        # sqlite3. This makes testing a bit tedious. Also, it does not give me
+        # that much of confidence that it would also work on mysql.
+        # Furtermore, we do not expect the queue to be very long at any moment.
+        return len(set(PlaylistSong.objects
+            .filter(Q(playlist=queue.playlist_id), Q(state=0) | Q(state=1))
+            .values_list('user')))
+    queue_users_gauge.labels(name=queue).set_function(_get_queue_distinct_users)
 
 
 def metrics(request):