Add Locality Load Balancing support (#258)

* Add Locality Load Balancing support

config/base/crds/istio_v1beta1_istio.yaml

@@ -280,6 +280,51 @@ spec:
                     type: object
                   type: array
               type: object
+            localityLB:
+              description: Locality based load balancing distribution or failover
+                settings.
+              properties:
+                distribute:
+                  description: 'Optional: only one of distribute or failover can be
+                    set. Explicitly specify loadbalancing weight across different
+                    zones and geographical locations. Refer to [Locality weighted
+                    load balancing](https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/load_balancing/locality_weight)
+                    If empty, the locality weight is set according to the endpoints
+                    number within it.'
+                  items:
+                    properties:
+                      from:
+                        description: Originating locality, '/' separated, e.g. 'region/zone'.
+                        type: string
+                      to:
+                        description: Map of upstream localities to traffic distribution
+                          weights. The sum of all weights should be == 100. Any locality
+                          not assigned a weight will receive no traffic.
+                        type: object
+                    type: object
+                  type: array
+                enabled:
+                  description: If set to true, locality based load balancing will
+                    be enabled
+                  type: boolean
+                failover:
+                  description: 'Optional: only failover or distribute can be set.
+                    Explicitly specify the region traffic will land on when endpoints
+                    in local region becomes unhealthy. Should be used together with
+                    OutlierDetection to detect unhealthy endpoints. Note: if no OutlierDetection
+                    specified, this will not take effect.'
+                  items:
+                    properties:
+                      from:
+                        description: Originating region.
+                        type: string
+                      to:
+                        description: Destination region the traffic will fail over
+                          to when endpoints in the 'from' region becomes unhealthy.
+                        type: string
+                    type: object
+                  type: array
+              type: object
             meshExpansion:
               description: If set to true, the pilot and citadel mtls will be exposed
                 on the ingress gateway also the remote istios will be connected through

config/samples/istio_v1beta1_istio.yaml

@@ -145,3 +145,15 @@ spec:
         accessToken: <access-token>
         secure: true
         cacertPath: /etc/lightstep/cacert.pem
+    localityLB:
+      enabled: false
+      # distribute:
+      # - from: "us-central1/*"
+      # to:
+      #     "us-central1/*": 80
+      #     "us-central2/*": 20
+      # failover:
+      # - from: us-east
+      #   to: eu-west
+      # - from: us-west
+      #   to: us-east

pkg/apis/istio/v1beta1/istio_types.go

@@ -305,6 +305,54 @@ type IstioCoreDNS struct {
 	Tolerations  []corev1.Toleration          `json:"tolerations,omitempty"`
 }
 
+// Describes how traffic originating in the 'from' zone is
+// distributed over a set of 'to' zones. Syntax for specifying a zone is
+// {region}/{zone} and terminal wildcards are allowed on any
+// segment of the specification. Examples:
+// * - matches all localities
+// us-west/* - all zones and sub-zones within the us-west region
+type LocalityLBDistributeConfiguration struct {
+	// Originating locality, '/' separated, e.g. 'region/zone'.
+	From string `json:"from,omitempty"`
+	// Map of upstream localities to traffic distribution weights. The sum of
+	// all weights should be == 100. Any locality not assigned a weight will
+	// receive no traffic.
+	To map[string]uint32 `json:"to,omitempty"`
+}
+
+// Specify the traffic failover policy across regions. Since zone
+// failover is supported by default this only needs to be specified for
+// regions when the operator needs to constrain traffic failover so that
+// the default behavior of failing over to any endpoint globally does not
+// apply. This is useful when failing over traffic across regions would not
+// improve service health or may need to be restricted for other reasons
+// like regulatory controls.
+type LocalityLBFailoverConfiguration struct {
+	// Originating region.
+	From string `json:"from,omitempty"`
+	// Destination region the traffic will fail over to when endpoints in
+	// the 'from' region becomes unhealthy.
+	To string `json:"to,omitempty"`
+}
+
+// Locality-weighted load balancing allows administrators to control the
+// distribution of traffic to endpoints based on the localities of where the
+// traffic originates and where it will terminate.
+type LocalityLBConfiguration struct {
+	// If set to true, locality based load balancing will be enabled
+	Enabled *bool `json:"enabled,omitempty"`
+	// Optional: only one of distribute or failover can be set.
+	// Explicitly specify loadbalancing weight across different zones and geographical locations.
+	// Refer to [Locality weighted load balancing](https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/load_balancing/locality_weight)
+	// If empty, the locality weight is set according to the endpoints number within it.
+	Distribute []*LocalityLBDistributeConfiguration `json:"distribute,omitempty"`
+	// Optional: only failover or distribute can be set.
+	// Explicitly specify the region traffic will land on when endpoints in local region becomes unhealthy.
+	// Should be used together with OutlierDetection to detect unhealthy endpoints.
+	// Note: if no OutlierDetection specified, this will not take effect.
+	Failover []*LocalityLBFailoverConfiguration `json:"failover,omitempty"`
+}
+
 // IstioSpec defines the desired state of Istio
 type IstioSpec struct {
 	// Contains the intended Istio version
@@ -397,6 +445,9 @@ type IstioSpec struct {
 	// Istio CoreDNS provides DNS resolution for services in multi mesh setups
 	IstioCoreDNS IstioCoreDNS `json:"istioCoreDNS,omitempty"`
 
+	// Locality based load balancing distribution or failover settings.
+	LocalityLB *LocalityLBConfiguration `json:"localityLB,omitempty"`
+
 	networkName  string
 	meshNetworks *MeshNetworks
 }

pkg/resources/common/configmap.go

@@ -104,7 +104,7 @@ func (r *Reconciler) meshConfig() string {
 		"defaultConfig":     defaultConfig,
 		"rootNamespace":     "istio-system",
 		"connectTimeout":    "10s",
-		"localityLbSetting": nil,
+		"localityLbSetting": r.getLocalityLBConfiguration(),
 	}
 
 	if util.PointerToBool(r.Config.Spec.UseMCP) {
@@ -117,6 +117,24 @@ func (r *Reconciler) meshConfig() string {
 	return string(marshaledConfig)
 }
 
+func (r *Reconciler) getLocalityLBConfiguration() *istiov1beta1.LocalityLBConfiguration {
+	var localityLbConfiguration *istiov1beta1.LocalityLBConfiguration
+
+	if r.Config.Spec.LocalityLB == nil || !util.PointerToBool(r.Config.Spec.LocalityLB.Enabled) {
+		return localityLbConfiguration
+	}
+
+	if r.Config.Spec.LocalityLB != nil {
+		localityLbConfiguration = r.Config.Spec.LocalityLB.DeepCopy()
+		localityLbConfiguration.Enabled = nil
+		if localityLbConfiguration.Distribute != nil && localityLbConfiguration.Failover != nil {
+			localityLbConfiguration.Failover = nil
+		}
+	}
+
+	return localityLbConfiguration
+}
+
 func (r *Reconciler) meshNetworks() string {
 	marshaledConfig, _ := yaml.Marshal(r.Config.Spec.GetMeshNetworks())
 	return string(marshaledConfig)

pkg/resources/pilot/deployment.go

@@ -143,6 +143,13 @@ func (r *Reconciler) containers() []apiv1.Container {
 		TerminationMessagePolicy: apiv1.TerminationMessageReadFile,
 	}
 
+	if r.Config.Spec.LocalityLB != nil && util.PointerToBool(r.Config.Spec.LocalityLB.Enabled) {
+		discoveryContainer.Env = append(discoveryContainer.Env, apiv1.EnvVar{
+			Name:  "PILOT_ENABLE_LOCALITY_LOAD_BALANCING",
+			Value: "1",
+		})
+	}
+
 	containers := []apiv1.Container{
 		discoveryContainer,
 	}