fix: add Loki schema config and chart preflight validation

ansible/roles/observability/tasks/main.yml

@@ -58,6 +58,14 @@
     dest: /tmp/loki-values.yaml
     mode: "0644"
 
+- name: Validate Loki Helm values
+  command: >-
+    helm template loki grafana/loki
+    --namespace {{ observability_namespace }}
+    --version {{ loki_chart_version }}
+    --values /tmp/loki-values.yaml
+  changed_when: false
+
 - name: Install Loki
   command: >-
     helm upgrade --install loki grafana/loki

ansible/roles/observability/templates/loki-values.yaml.j2

@@ -4,6 +4,15 @@ loki:
   auth_enabled: false
   commonConfig:
     replication_factor: 1
+  schemaConfig:
+    configs:
+      - from: "2024-01-01"
+        store: tsdb
+        object_store: filesystem
+        schema: v13
+        index:
+          prefix: loki_index_
+          period: 24h
   storage:
     type: filesystem