Add opt-in config checksum annotation for auto pod restarts (#76)

ConfigMap changes don't trigger pod restarts, so config updates
silently fail to take effect after helm upgrade.  This adds an opt-in
`restartOnConfigChange` value (default false) that injects a
`checksum/config` pod annotation, triggering rolling restarts when the
rendered config changes.

This is related to #15 and the closed #22.

Author: NJAldwin

README.md

@@ -135,6 +135,19 @@ podAntiAffinity:
   type: soft # "soft" (preferred) or "hard" (required)
 ```
 
+### Config Change Restarts
+
+By default, ConfigMap changes are not automatically picked up by
+running pods. Enable `restartOnConfigChange` to trigger a rolling
+restart whenever the rendered config changes:
+
+```yaml
+restartOnConfigChange: true
+```
+
+This injects a `checksum/config` pod annotation that changes when the
+config template output changes, causing Kubernetes to roll the pods.
+
 ### ExternalSecrets Integration
 
 Securely manage credentials using ExternalSecrets operator:

templates/deployment.yaml

@@ -30,9 +30,14 @@ spec:
     metadata:
       labels:
         {{- include "pgdog.selectorLabels" . | nindent 8 }}
-      {{- if .Values.podAnnotations }}
+      {{- if or .Values.restartOnConfigChange .Values.podAnnotations }}
       annotations:
+        {{- if .Values.restartOnConfigChange }}
+        checksum/config: {{ include (print $.Template.BasePath "/config.yaml") . | sha256sum }}
+        {{- end }}
+        {{- if .Values.podAnnotations }}
         {{- toYaml .Values.podAnnotations | nindent 8 }}
+        {{- end }}
       {{- end }}
     spec:
       {{- if .Values.serviceAccount.create }}

values.yaml

@@ -19,6 +19,11 @@ annotations: {}
 # allows adding custom annotations to the pods
 podAnnotations: {}
 
+# restartOnConfigChange triggers a rolling restart when pgdog config changes.
+# Disabled by default; enable if you don't have a hot-reload mechanism (e.g. SIGHUP sidecar).
+# See: https://github.com/pgdogdev/helm/issues/15
+# restartOnConfigChange: false
+
 # clusterName identifies the Kubernetes cluster (optional)
 # When set, this will be added as a label to all Prometheus metrics
 # clusterName: ""