metrics: Make metrics actually usable

core/core/metrics.py

@@ -1,16 +1,36 @@
 from django.apps import apps
 from prometheus_client.core import CounterMetricFamily, REGISTRY
+from django.db.models import Case, Value, When, BooleanField, Count
+from inventory.models import Item
+import logging
 
-class ModelCountCollector(object):
+class ItemCountCollector(object):
 
     def collect(self):
-        counter = CounterMetricFamily('model_count', 'Number of objects per model', labels=['model', 'app'])
+        counter = CounterMetricFamily("item_count", "Current number of items", labels=['event', 'state'])
-        yield counter
+
-        if not apps.models_ready or not apps.apps_ready:
-            return
-        for app_name, app_config in apps.app_configs.items():
-            for model in app_config.get_models():
-                counter.add_metric([model.__name__, app_name], model.objects.count())
         yield counter
 
-REGISTRY.register(ModelCountCollector())
+        if not apps.models_ready or not apps.apps_ready:
+            return
+
+        queryset = (
+            Item.all_objects
+                .annotate(
+                    returned=Case(
+                        When(returned_at__isnull=False, then=Value(False)),
+                        default=Value(True),
+                        output_field=BooleanField()
+                    )
+                )
+                .values('event__slug', 'returned', 'event_id')
+                .annotate(amount=Count('id'))
+                .order_by('event__slug', 'returned')  # Optional: order by slug and returned
+        )
+
+        for e in queryset:
+            counter.add_metric([e["event__slug"].lower(), str(e["returned"])], e["amount"])
+
+        yield counter
+
+REGISTRY.register(ItemCountCollector())