FEAT(alertmanager): add ServiceMonitor

- Create servicemonitor.yaml for Prometheus to scrape Alertmanager
- alertmanager chart does not include ServiceMonitor, must be added separately
- Enables Grafana Alertmanager dashboard to display data

alertmanager/helm-values.yaml

@@ -13,13 +13,6 @@ resources:
     cpu: 10m
     memory: 32Mi
 
-# Prometheus ServiceMonitor 설정
-serviceMonitor:
-  enabled: true
-  additionalLabels:
-    release: prometheus
-  namespace: prometheus
-
 # Disable default config - use secret instead
 config:
   enabled: false

alertmanager/kustomization.yaml

@@ -2,4 +2,5 @@ apiVersion: kustomize.config.k8s.io/v1beta1
 kind: Kustomization
 resources:
   - ingress.yaml
+  - servicemonitor.yaml
   - vault/alertmanager-secrets.yaml

alertmanager/servicemonitor.yaml

@@ -0,0 +1,27 @@
+apiVersion: monitoring.coreos.com/v1
+kind: ServiceMonitor
+metadata:
+  name: alertmanager
+  namespace: prometheus
+  labels:
+    release: prometheus
+spec:
+  endpoints:
+    - port: http
+      path: /metrics
+      scheme: http
+      interval: 60s
+      relabelings:
+        - targetLabel: cluster
+          replacement: "mayne-cluster"
+        # Drop alertmanager-headless to avoid duplicate metrics
+        - sourceLabels: [__meta_kubernetes_service_name]
+          regex: alertmanager-headless
+          action: drop
+  namespaceSelector:
+    matchNames:
+      - alertmanager
+  selector:
+    matchLabels:
+      app.kubernetes.io/instance: alertmanager
+      app.kubernetes.io/name: alertmanager