root: add error handling for prometheus view

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

authentik/root/monitoring.py

@@ -1,14 +1,15 @@
 """Metrics view"""
 from base64 import b64encode
 
+import prometheus_client
 from django.conf import settings
 from django.db import connections
 from django.db.utils import OperationalError
 from django.dispatch import Signal
 from django.http import HttpRequest, HttpResponse
 from django.views import View
-from django_prometheus.exports import ExportToDjangoView
 from django_redis import get_redis_connection
+from prometheus_client import multiprocess
 from redis.exceptions import RedisError
 
 monitoring_set = Signal()
@@ -31,7 +32,13 @@ class MetricsView(View):
 
         monitoring_set.send_robust(self)
 
-        return ExportToDjangoView(request)
+        registry = prometheus_client.CollectorRegistry()
+        multiprocess.MultiProcessCollector(registry)
+        try:
+            metrics_page = prometheus_client.generate_latest(registry)
+            return HttpResponse(metrics_page, content_type=prometheus_client.CONTENT_TYPE_LATEST)
+        except (UnicodeDecodeError, KeyError):
+            return HttpResponse(status_code=500)
 
 
 class LiveView(View):