Add Prometheus metrics endpoint for KYC monitoring

kyc_app/views.py

@@ -3,9 +3,16 @@ Views for KYC API.
 
 Authentication is handled by GRAPHENE MIDDLEWARE in settings.py
 """
+import os
+from datetime import timedelta
+
+from django.db.models import Count, Q
+from django.http import HttpResponse
+from django.utils import timezone
 from graphene_django.views import GraphQLView
 
 from .graphql_middleware import UserJWTMiddleware
+from .models import KYCProfile
 
 
 class UserGraphQLView(GraphQLView):
@@ -47,3 +54,37 @@ class PublicGraphQLView(GraphQLView):
         # Use optional auth middleware that doesn't fail on missing token
         kwargs['middleware'] = [OptionalUserJWTMiddleware()]
         super().__init__(*args, **kwargs)
+
+
+def metrics_view(request):
+    """Prometheus metrics endpoint for KYC monitoring status."""
+    stale_days = int(os.getenv("KYC_STALE_DAYS", "90"))
+    cutoff = timezone.now() - timedelta(days=stale_days)
+
+    stats = KYCProfile.objects.filter(workflow_status="active").aggregate(
+        total=Count("id"),
+        stale=Count("id", filter=Q(updated_at__lt=cutoff) | Q(updated_at__isnull=True)),
+        fresh=Count("id", filter=Q(updated_at__gte=cutoff)),
+    )
+
+    total = int(stats.get("total") or 0)
+    stale = int(stats.get("stale") or 0)
+    fresh = int(stats.get("fresh") or 0)
+    ratio = 0.0 if total == 0 else stale / total
+
+    payload = (
+        "# HELP kyc_monitoring_total Total active profiles in monitoring\n"
+        "# TYPE kyc_monitoring_total gauge\n"
+        f"kyc_monitoring_total {total}\n"
+        "# HELP kyc_monitoring_stale Stale profiles (no refresh within window)\n"
+        "# TYPE kyc_monitoring_stale gauge\n"
+        f"kyc_monitoring_stale {stale}\n"
+        "# HELP kyc_monitoring_fresh Fresh profiles (refreshed within window)\n"
+        "# TYPE kyc_monitoring_fresh gauge\n"
+        f"kyc_monitoring_fresh {fresh}\n"
+        "# HELP kyc_monitoring_stale_ratio Stale / total ratio\n"
+        "# TYPE kyc_monitoring_stale_ratio gauge\n"
+        f"kyc_monitoring_stale_ratio {ratio}\n"
+    )
+
+    return HttpResponse(payload, content_type="text/plain; version=0.0.4; charset=utf-8")