Add Pod Anti Affinity (#489)

* Add Pod Anti Affinity

pkg/apis/acid.zalan.do/v1/operator_configuration_type.go

@@ -60,6 +60,8 @@ type KubernetesMetaConfiguration struct {
 	// TODO: use namespacedname
 	PodEnvironmentConfigMap string `json:"pod_environment_configmap,omitempty"`
 	PodPriorityClassName    string `json:"pod_priority_class_name,omitempty"`
+	EnablePodAntiAffinity                  bool                  `json:"enable_pod_antiaffinity" default:"false"`
+	PodAntiAffinityTopologyKey			   string                `name:"pod_antiaffinity_topology_key" default:"kubernetes.io/hostname"`
 }
 
 // PostgresPodResourcesDefaults defines the spec of default resources

pkg/cluster/k8sres.go

@@ -290,6 +290,26 @@ func nodeAffinity(nodeReadinessLabel map[string]string) *v1.Affinity {
 	}
 }
 
+func generatePodAffinity(labels labels.Set, topologyKey string, nodeAffinity *v1.Affinity) *v1.Affinity {
+	// generate pod anti-affinity to avoid multiple pods of the same Postgres cluster in the same topology , e.g. node
+	podAffinity := v1.Affinity{
+		PodAntiAffinity: &v1.PodAntiAffinity{
+			RequiredDuringSchedulingIgnoredDuringExecution: []v1.PodAffinityTerm{{
+				LabelSelector: &metav1.LabelSelector{
+					MatchLabels: labels,
+				},
+				TopologyKey: topologyKey,
+			}},
+		},
+	}
+
+	if nodeAffinity != nil && nodeAffinity.NodeAffinity != nil {
+		podAffinity.NodeAffinity = nodeAffinity.NodeAffinity
+	}
+
+	return &podAffinity
+}
+
 func tolerations(tolerationsSpec *[]v1.Toleration, podToleration map[string]string) []v1.Toleration {
 	// allow to override tolerations by postgresql manifest
 	if len(*tolerationsSpec) > 0 {
@@ -419,6 +439,8 @@ func generatePodTemplate(
 	kubeIAMRole string,
 	priorityClassName string,
 	shmVolume bool,
+	podAntiAffinity bool,
+	podAntiAffinityTopologyKey string,
 ) (*v1.PodTemplateSpec, error) {
 
 	terminateGracePeriodSeconds := terminateGracePeriod
@@ -437,7 +459,9 @@ func generatePodTemplate(
 		addShmVolume(&podSpec)
 	}
 
-	if nodeAffinity != nil {
+	if podAntiAffinity {
+		podSpec.Affinity = generatePodAffinity(labels, podAntiAffinityTopologyKey, nodeAffinity)
+	} else if nodeAffinity != nil {
 		podSpec.Affinity = nodeAffinity
 	}
 
@@ -813,7 +837,9 @@ func (c *Cluster) generateStatefulSet(spec *acidv1.PostgresSpec) (*v1beta1.State
 		c.OpConfig.PodServiceAccountName,
 		c.OpConfig.KubeIAMRole,
 		effectivePodPriorityClassName,
-		mountShmVolumeNeeded(c.OpConfig, spec)); err != nil {
+		mountShmVolumeNeeded(c.OpConfig, spec),
+		c.OpConfig.EnablePodAntiAffinity,
+		c.OpConfig.PodAntiAffinityTopologyKey); err != nil {
 		return nil, fmt.Errorf("could not generate pod template: %v", err)
 	}
 

pkg/controller/operator_config.go

@@ -53,6 +53,9 @@ func (c *Controller) importConfigurationFromCRD(fromCRD *acidv1.OperatorConfigur
 	result.NodeReadinessLabel = fromCRD.Kubernetes.NodeReadinessLabel
 	result.PodPriorityClassName = fromCRD.Kubernetes.PodPriorityClassName
 
+	result.EnablePodAntiAffinity = fromCRD.Kubernetes.EnablePodAntiAffinity;
+	result.PodAntiAffinityTopologyKey = fromCRD.Kubernetes.PodAntiAffinityTopologyKey;
+
 	result.DefaultCPURequest = fromCRD.PostgresPodResources.DefaultCPURequest
 	result.DefaultMemoryRequest = fromCRD.PostgresPodResources.DefaultMemoryRequest
 	result.DefaultCPULimit = fromCRD.PostgresPodResources.DefaultCPULimit

pkg/util/config/config.go

@@ -95,6 +95,8 @@ type Config struct {
 	EnableMasterLoadBalancer               bool   `name:"enable_master_load_balancer" default:"true"`
 	EnableReplicaLoadBalancer              bool   `name:"enable_replica_load_balancer" default:"false"`
 	CustomServiceAnnotations			   map[string]string `name:"custom_service_annotations"`
+	EnablePodAntiAffinity                  bool   `name:"enable_pod_antiaffinity" default:"false"`
+	PodAntiAffinityTopologyKey			   string `name:"pod_antiaffinity_topology_key" default:"kubernetes.io/hostname"`
 	// deprecated and kept for backward compatibility
 	EnableLoadBalancer       *bool             `name:"enable_load_balancer"`
 	MasterDNSNameFormat      StringTemplate    `name:"master_dns_name_format" default:"{cluster}.{team}.{hostedzone}"`