feat: replace pod IP with DNS name for Patroni connectivity

Replace LISTEN_ADDR (pod IP) with POD_DNS_NAME (DNS FQDN) for Patroni
REST API and PostgreSQL connect addresses to enable stable addressing
across pod restarts.

Changes:
- Add POD_NAME, HEADLESS_SERVICE, and POD_DNS_NAME environment variables
  to Patroni StatefulSet pods
- Create patroni-headless Service for DNS-based pod discovery
- Update patroni.config.yaml to use ${POD_DNS_NAME} for pod_ip,
  connect_address (PostgreSQL), and connect_address (REST API)
- Register patroni-headless service creation in reconciler

Reasons:
- Pod IPs are ephemeral and change on restarts, causing connection issues
- DNS names (pod-name.service.namespace.svc.cluster.local) are stable
- Improves reliability of Patroni DCS registration and cluster communication
- Aligns with Kubernetes best practices for StatefulSet networking

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: vlsi

build/configs/patroni.config.yaml

@@ -51,7 +51,7 @@ kubernetes:
     app: ${PATRONI_CLUSTER_NAME}
   role_label: pgtype
   scope_label: app
-  pod_ip: ${LISTEN_ADDR}
+  pod_ip: ${POD_DNS_NAME}
 postgresql:
   authentication:
     replication:
@@ -67,17 +67,17 @@ postgresql:
     on_role_change: /setup_endpoint_callback.py
     on_start: /setup_endpoint_callback.py
     on_stop: /setup_endpoint_callback.py
-  connect_address: ${LISTEN_ADDR}:5432
+  connect_address: ${POD_DNS_NAME}:5432
   data_dir: /var/lib/pgsql/data/postgresql_${NODE_NAME}
-  listen: '0.0.0.0, ::0:5432'
+  listen: '*:5432'
   parameters:
     unix_socket_directories: /var/run/postgresql, /tmp
   pgpass: /tmp/pgpass0
 restapi:
-  connect_address: ${LISTEN_ADDR}:8008
-  listen: ${LISTEN_ADDR}:8008
+  connect_address: ${POD_DNS_NAME}:8008
+  listen: '*:8008'
 tags:
   clonefrom: false
   nofailover: ${DR_MODE}
   noloadbalance: false
-  nosync: false
+  nosync: false

charts/patroni-services/values.yaml

@@ -410,7 +410,7 @@ connectionPooler:
       '*': "host=pg-patroni-direct port=5432"
     pgbouncer:
       listen_port: '6432'
-      listen_addr: '0.0.0.0'
+      listen_addr: '*'
       auth_type: 'md5'
       auth_file: '/etc/pgbouncer/userlist.txt'
       auth_user: 'pgbouncer'

docs/public/installation.md

@@ -833,7 +833,7 @@ For more information on how to do the Major Upgrade of PostgreSQL, please, follo
 ```yaml
     pgbouncer:
       listen_port: '6432'
-      listen_addr: '0.0.0.0'
+      listen_addr: '*'
       auth_type: 'md5'
       auth_file: '/etc/pgbouncer/userlist.txt'
       auth_user: 'pgbouncer'

pkg/deployment/patroni.go

@@ -242,6 +242,23 @@ func NewPatroniStatefulset(cr *patroniv1.PatroniCore, deploymentIdx int, cluster
 										},
 									},
 								},
+								{
+									Name: "POD_NAME",
+									ValueFrom: &corev1.EnvVarSource{
+										FieldRef: &corev1.ObjectFieldSelector{
+											APIVersion: "v1",
+											FieldPath:  "metadata.name",
+										},
+									},
+								},
+								{
+									Name:  "HEADLESS_SERVICE",
+									Value: "patroni-headless",
+								},
+								{
+									Name:  "POD_DNS_NAME",
+									Value: "$(POD_NAME).$(HEADLESS_SERVICE).$(POD_NAMESPACE).svc.cluster.local",
+								},
 								{
 									Name: "PG_RESOURCES_LIMIT_MEM",
 									ValueFrom: &corev1.EnvVarSource{
@@ -309,7 +326,7 @@ func NewPatroniStatefulset(cr *patroniv1.PatroniCore, deploymentIdx int, cluster
 					DNSPolicy:                     corev1.DNSClusterFirst,
 				},
 			},
-			ServiceName:                          "backrest-headless",
+			ServiceName:                          "patroni-headless",
 			PodManagementPolicy:                  appsv1.OrderedReadyPodManagement,
 			UpdateStrategy:                       appsv1.StatefulSetUpdateStrategy{Type: appsv1.RollingUpdateStatefulSetStrategyType},
 			RevisionHistoryLimit:                 ptr.To[int32](10),

pkg/deployment/pgbackrest.go

@@ -182,6 +182,30 @@ func GetBackrestHeadless() *corev1.Service {
 	}
 }
 
+func GetPatroniHeadless(clusterName string) *corev1.Service {
+	labels := map[string]string{"app": clusterName}
+	ports := []corev1.ServicePort{
+		{Name: "postgresql", Port: 5432},
+		{Name: "patroni-api", Port: 8008},
+	}
+	return &corev1.Service{
+		TypeMeta: metav1.TypeMeta{
+			APIVersion: "v1",
+			Kind:       "Service",
+		},
+		ObjectMeta: metav1.ObjectMeta{
+			Name:      "patroni-headless",
+			Namespace: util.GetNameSpace(),
+		},
+
+		Spec: corev1.ServiceSpec{
+			Selector:  labels,
+			Ports:     ports,
+			ClusterIP: "None",
+		},
+	}
+}
+
 func getPgBackRestSettings(pgBackrestSpec *v1.PgBackRest, isStandby bool) string {
 	var listSettings []string
 	listSettings = append(listSettings, "[global]")

pkg/reconciler/patroni.go

@@ -473,6 +473,14 @@ func (r *PatroniReconciler) processPatroniServices(cr *v1.PatroniCore, patroniSp
 			}
 		}
 	}
+
+	// Create patroni headless service for DNS-based pod discovery
+	patroniHeadless := deployment.GetPatroniHeadless(r.cluster.ClusterName)
+	if err := r.helper.ResourceManager.CreateOrUpdateService(patroniHeadless); err != nil {
+		logger.Error(fmt.Sprintf("Cannot create service %s", patroniHeadless.Name), zap.Error(err))
+		return err
+	}
+
 	return nil
 }