v-m/alerts: Add alerts for Paperless-ngx

victoria-metrics/alerts.yml

@@ -165,3 +165,15 @@ groups:
         The size of the Restic backup for a particular client has not changed
         in at least 7 days.  This may indicate that the backup configuration
         is incorrect.
+
+- name: Paperless-ngx
+  rules:
+  - alert: Celery tasks failed
+    expr: >-
+      flower_events_total{job="paperless-ngx", type="task-failed"} > 0
+    annotations:
+      summary: One or more Celery tasks have failed
+      description: >-
+        Failing Celery tasks may indicate a problem with the Paperless-ngx
+        deployment and can result in data loss.  Check the Paperless-ngx logs
+        for details about the task failures.