Preserve sync quorum in primary PDB without master selector (#3119)

* Use minAvalable=SynchronousNodeCount + 1 in primary PDB when master selector is disabled

---------

Co-authored-by: Felix Kunde <felix-kunde@gmx.de>
Co-authored-by: Ida Novindasari <idanovinda@gmail.com>

pkg/cluster/k8sres.go

@@ -2278,6 +2278,12 @@ func (c *Cluster) generatePrimaryPodDisruptionBudget() *policyv1.PodDisruptionBu
 		labels[c.OpConfig.PodRoleLabel] = string(Master)
 	}
 
+	// When master selector is disabled and synchronous_mode_strict is on, require
+	// master + synchronous_node_count (default 1) healthy pods for write quorum.
+	if pdbMasterLabelSelector != nil && !*pdbMasterLabelSelector && minAvailable.IntVal > 0 && c.Spec.SynchronousModeStrict {
+		minAvailable = intstr.FromInt32(int32(c.Spec.SynchronousNodeCount + 1))
+	}
+
 	return &policyv1.PodDisruptionBudget{
 		ObjectMeta: metav1.ObjectMeta{
 			Name:            c.PrimaryPodDisruptionBudgetName(),

pkg/cluster/k8sres_test.go

@@ -2691,13 +2691,13 @@ func TestGeneratePodDisruptionBudget(t *testing.T) {
 				k8sutil.KubernetesClient{},
 				acidv1.Postgresql{
 					ObjectMeta: metav1.ObjectMeta{Name: "myapp-database", Namespace: "myapp"},
-					Spec:       acidv1.PostgresSpec{TeamID: "myapp", NumberOfInstances: 3}},
+					Spec:       acidv1.PostgresSpec{TeamID: "myapp", NumberOfInstances: 3, Patroni: acidv1.Patroni{SynchronousModeStrict: true, SynchronousNodeCount: 1}}},
 				logger,
 				eventRecorder),
 			check: []func(cluster *Cluster, podDisruptionBudget *policyv1.PodDisruptionBudget) error{
 				testPodDisruptionBudgetOwnerReference,
 				hasName("postgres-myapp-database-pdb"),
-				hasMinAvailable(1),
+				hasMinAvailable(2),
 				testLabelsAndSelectors(true),
 			},
 		},