add postgres alerts

k8s/monitoring/alerts-postgres.yaml

@@ -0,0 +1,20 @@
+apiVersion: monitoring.coreos.com/v1
+kind: PrometheusRule
+metadata:
+  labels:
+    prometheus: k8s
+    role: alert-rules
+  name: postgres-operator-alerts
+  namespace: monitoring
+spec:
+  groups:
+  - name: postgres-operator
+    rules:
+    - alert: PatroniHasNoLeader
+      expr: (max by (scope) (patroni_master) < 1) and (max by (scope) (patroni_standby_leader) < 1)
+      for: 0m
+      labels:
+        severity: critical
+      annotations:
+        summary: Patroni has no Leader (instance {{ $labels.instance }})
+        description: "A leader node (neither primary nor standby) cannot be found inside the cluster {{ $labels.scope }}\n  VALUE = {{ $value }}\n  LABELS = {{ $labels }}"

k8s/monitoring/kustomization.yaml

@@ -2,6 +2,7 @@ apiVersion: kustomize.config.k8s.io/v1beta1
 kind: Kustomization
 namespace: monitoring
 resources:
+  - alerts-postgres.yaml
   - promtail.yaml
   - ingresses.yaml
   - secrets.yaml