feat: leader election (#17)

* feat: leader election

* app version

Author: levkk

Chart.yaml

@@ -2,5 +2,5 @@ apiVersion: v2
 name: pgdog-control
 description: PgDog Control
 type: application
-version: 0.2.12
-appVersion: "1a6d7fd0"
+version: 0.2.13
+appVersion: "29a6513b"

README.md

@@ -267,6 +267,7 @@ When `control.rbac.create` is `true` (default), the chart renders:
 
 - A `ServiceAccount` for the control pod. If `control.aws.roleArn` is set, the ServiceAccount also carries the `eks.amazonaws.com/role-arn` annotation, which is what EKS IRSA looks for when handing the pod temporary AWS credentials.
 - A `ClusterRole` and `ClusterRoleBinding` granting **read-only** access cluster-wide. This is enough for the dashboard to list namespaces and read deployments, statefulsets, pods, services, configmaps, and secrets in any namespace. It cannot change anything. Pod logs are included so the deployment log view works.
+- A namespace-scoped `Role` and `RoleBinding` in the release namespace granting access to `coordination.k8s.io` `Lease` objects for control-plane leader election.
 - For each namespace you list in `control.rbac.writeNamespaces`, a namespace-scoped `Role` and `RoleBinding` granting **write** access (create, update, patch, delete) on the resources PgDog actually manages: deployments, statefulsets, services, configmaps, secrets, service accounts, roles, role bindings, and pod disruption budgets. Namespaces not on the list stay strictly read-only.
 
 A typical setup grants write access only to the namespaces where you want PgDog clusters to live:

templates/configmap.yaml

@@ -106,6 +106,26 @@ data:
     {{- end }}
     {{- end }}
 
+    {{- with $config.leader }}
+
+    [leader]
+    {{- if hasKey . "enabled" }}
+    enabled = {{ .enabled }}
+    {{- end }}
+    {{- with .lease_name }}
+    lease_name = {{ . | quote }}
+    {{- end }}
+    {{- with .lease_duration_secs }}
+    lease_duration_secs = {{ . }}
+    {{- end }}
+    {{- with .renew_interval_secs }}
+    renew_interval_secs = {{ . }}
+    {{- end }}
+    {{- with .release_timeout_secs }}
+    release_timeout_secs = {{ . }}
+    {{- end }}
+    {{- end }}
+
     {{- with $config.helm }}
 
     [helm]

templates/deployment.yaml

@@ -9,9 +9,22 @@ spec:
   selector:
     matchLabels:
       {{- include "pgdog-control.selectorLabels" . | nindent 6 }}
+  # Readiness is leader-aware so only the elected control pod receives
+  # Service traffic. New pods normally start as followers, so they do not
+  # become Ready while the old leader still holds the Lease. Allowing the
+  # whole old ReplicaSet to be unavailable lets Kubernetes terminate the
+  # old leader, release the Lease, and promote a new-version pod instead
+  # of waiting forever for a follower to become Ready.
+  strategy:
+    type: RollingUpdate
+    rollingUpdate:
+      maxSurge: 0
+      maxUnavailable: 100%
   template:
     metadata:
       annotations:
+        meta.helm.sh/release-name: {{ .Release.Name | quote }}
+        meta.helm.sh/release-namespace: {{ .Release.Namespace | quote }}
         # Roll the deployment when any rendered config / secret content
         # changes. Each annotation hashes the *template output*, not
         # values directly, so transformations applied inside the
@@ -169,12 +182,12 @@ spec:
           failureThreshold: 3
         readinessProbe:
           httpGet:
-            path: /healthz
+            path: /readyz
             port: {{ .Values.control.port }}
           initialDelaySeconds: 30
-          periodSeconds: 10
-          timeoutSeconds: 3
-          failureThreshold: 3
+          periodSeconds: 2
+          timeoutSeconds: 1
+          failureThreshold: 1
       volumes:
       - name: config
         configMap:

templates/rbac.yaml

@@ -54,6 +54,35 @@ subjects:
   - kind: ServiceAccount
     name: {{ include "pgdog-control.control.serviceAccountName" . }}
     namespace: {{ .Release.Namespace }}
+---
+# Namespace-scoped access for control-plane leader election.
+apiVersion: rbac.authorization.k8s.io/v1
+kind: Role
+metadata:
+  name: {{ include "pgdog-control.control.clusterFullname" . }}-leader
+  namespace: {{ .Release.Namespace }}
+  labels:
+    {{- include "pgdog-control.labels" . | nindent 4 }}
+rules:
+  - apiGroups: ["coordination.k8s.io"]
+    resources: ["leases"]
+    verbs: ["get", "list", "watch", "create", "update", "patch", "delete"]
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: RoleBinding
+metadata:
+  name: {{ include "pgdog-control.control.clusterFullname" . }}-leader
+  namespace: {{ .Release.Namespace }}
+  labels:
+    {{- include "pgdog-control.labels" . | nindent 4 }}
+roleRef:
+  apiGroup: rbac.authorization.k8s.io
+  kind: Role
+  name: {{ include "pgdog-control.control.clusterFullname" . }}-leader
+subjects:
+  - kind: ServiceAccount
+    name: {{ include "pgdog-control.control.serviceAccountName" . }}
+    namespace: {{ .Release.Namespace }}
 {{- range $ns := .Values.control.rbac.writeNamespaces }}
 ---
 # Namespace-scoped write access for workloads the control plane manages.

test/values-full.yaml

@@ -35,6 +35,12 @@ control:
       autoreload: "immediately"
     autoscaling:
       pool_size: true
+    leader:
+      enabled: true
+      lease_name: pgdog-control-leader
+      lease_duration_secs: 20
+      renew_interval_secs: 7
+      release_timeout_secs: 4
     helm:
       chart: pgdog
       repo: pgdogdev

values.yaml

@@ -107,6 +107,12 @@ control:
       # autoreload: off
     autoscaling: {}
       # pool_size: false
+    leader: {}
+      # enabled: true
+      # lease_name: ""              # Empty means derive from Helm release.
+      # lease_duration_secs: 15
+      # renew_interval_secs: 5
+      # release_timeout_secs: 3
     helm: {}
       # chart: pgdog
       # repo: pgdogdev