LoadBalancer in BackendTrafficPolicy (#2063)

* LoadBalancer in BackendTrafficPolicy

Fixes: #1105

Signed-off-by: Arko Dasgupta <arko@tetrate.io>

* tests

Signed-off-by: Arko Dasgupta <arko@tetrate.io>

---------

Signed-off-by: Arko Dasgupta <arko@tetrate.io>

api/v1alpha1/backendtrafficpolicy_types.go

@@ -48,7 +48,13 @@ type BackendTrafficPolicySpec struct {
 
 	// RateLimit allows the user to limit the number of incoming requests
 	// to a predefined value based on attributes within the traffic flow.
+	// +optional
 	RateLimit *RateLimitFilterSpec `json:"rateLimit,omitempty"`
+
+	// LoadBalancer policy to apply when routing traffic from the gateway to
+	// the backend endpoints
+	// +optional
+	LoadBalancer *LoadBalancer `json:"loadBalancer,omitempty"`
 }
 
 // BackendTrafficPolicyStatus defines the state of BackendTrafficPolicy

api/v1alpha1/loadbalancer_types.go

@@ -0,0 +1,55 @@
+// Copyright Envoy Gateway Authors
+// SPDX-License-Identifier: Apache-2.0
+// The full text of the Apache license is available in the LICENSE file at
+// the root of the repo.
+
+package v1alpha1
+
+// LoadBalancer defines the load balancer policy to be applied.
+// +union
+type LoadBalancer struct {
+	// Type decides the type of Load Balancer policy.
+	// Valid RateLimitType values are
+	// "ConsistentHash",
+	// "LeastRequest",
+	// "Random",
+	// "RoundRobin",
+	//
+	// +unionDiscriminator
+	Type LoadBalancerType `json:"type"`
+	// ConsistentHash defines the configuration when the load balancer type is
+	// set to ConsistentHash
+	//
+	// +optional
+	ConsistentHash *ConsistentHash `json:"consistentHash,omitempty"`
+}
+
+// LoadBalancerType specifies the types of LoadBalancer.
+// +kubebuilder:validation:Enum=ConsistentHash;LeastRequest;Random;RoundRobin
+type LoadBalancerType string
+
+const (
+	// ConsistentHashLoadBalancerType load balancer policy.
+	ConsistentHashLoadBalancerType LoadBalancerType = "ConsistentHash"
+	// LeastRequestLoadBalancerType load balancer policy.
+	LeastRequestLoadBalancerType LoadBalancerType = "LeastRequest"
+	// RandomLoadBalancerType load balancer policy.
+	RandomLoadBalancerType LoadBalancerType = "Random"
+	// RoundRobinLoadBalancerType load balancer policy.
+	RoundRobinLoadBalancerType LoadBalancerType = "RoundRobin"
+)
+
+// ConsistentHash defines the configuration related to the consistent hash
+// load balancer policy
+type ConsistentHash struct {
+	Type ConsistentHashType `json:"type"`
+}
+
+// ConsistentHashType defines the type of input to hash on.
+// +kubebuilder:validation:Enum=SourceIP
+type ConsistentHashType string
+
+const (
+	// SourceIPConsistentHashType hashes based on the source IP address.
+	SourceIPConsistentHashType ConsistentHashType = "SourceIP"
+)

charts/gateway-helm/crds/generated/gateway.envoyproxy.io_backendtrafficpolicies.yaml

@@ -44,6 +44,36 @@ spec:
           spec:
             description: spec defines the desired state of BackendTrafficPolicy.
             properties:
+              loadBalancer:
+                description: LoadBalancer policy to apply when routing traffic from
+                  the gateway to the backend endpoints
+                properties:
+                  consistentHash:
+                    description: ConsistentHash defines the configuration when the
+                      load balancer type is set to ConsistentHash
+                    properties:
+                      type:
+                        description: ConsistentHashType defines the type of input
+                          to hash on.
+                        enum:
+                        - SourceIP
+                        type: string
+                    required:
+                    - type
+                    type: object
+                  type:
+                    description: Type decides the type of Load Balancer policy. Valid
+                      RateLimitType values are "ConsistentHash", "LeastRequest", "Random",
+                      "RoundRobin",
+                    enum:
+                    - ConsistentHash
+                    - LeastRequest
+                    - Random
+                    - RoundRobin
+                    type: string
+                required:
+                - type
+                type: object
               rateLimit:
                 description: RateLimit allows the user to limit the number of incoming
                   requests to a predefined value based on attributes within the traffic

internal/gatewayapi/backendtrafficpolicy.go

@@ -238,11 +238,18 @@ func resolveBTPolicyRouteTargetRef(policy *egv1a1.BackendTrafficPolicy, routes m
 }
 
 func (t *Translator) translateBackendTrafficPolicyForRoute(policy *egv1a1.BackendTrafficPolicy, route RouteContext, xdsIR XdsIRMap) {
+	var (
+		rl *ir.RateLimit
+		lb *ir.LoadBalancer
+	)
+
 	// Build IR
-	var rl *ir.RateLimit
 	if policy.Spec.RateLimit != nil {
 		rl = t.buildRateLimit(policy)
 	}
+	if policy.Spec.LoadBalancer != nil {
+		lb = t.buildLoadBalancer(policy)
+	}
 
 	// Apply IR to all relevant routes
 	prefix := irRoutePrefix(route)
@@ -252,6 +259,7 @@ func (t *Translator) translateBackendTrafficPolicyForRoute(policy *egv1a1.Backen
 				// Apply if there is a match
 				if strings.HasPrefix(r.Name, prefix) {
 					r.RateLimit = rl
+					r.LoadBalancer = lb
 				}
 			}
 		}
@@ -260,12 +268,18 @@ func (t *Translator) translateBackendTrafficPolicyForRoute(policy *egv1a1.Backen
 }
 
 func (t *Translator) translateBackendTrafficPolicyForGateway(policy *egv1a1.BackendTrafficPolicy, gateway *GatewayContext, xdsIR XdsIRMap) {
+	var (
+		rl *ir.RateLimit
+		lb *ir.LoadBalancer
+	)
+
 	// Build IR
-	var rl *ir.RateLimit
 	if policy.Spec.RateLimit != nil {
 		rl = t.buildRateLimit(policy)
 	}
-
+	if policy.Spec.LoadBalancer != nil {
+		lb = t.buildLoadBalancer(policy)
+	}
 	// Apply IR to all the routes within the specific Gateway
 	// If the feature is already set, then skip it, since it must be have
 	// set by a policy attaching to the route
@@ -279,6 +293,9 @@ func (t *Translator) translateBackendTrafficPolicyForGateway(policy *egv1a1.Back
 			if r.RateLimit == nil {
 				r.RateLimit = rl
 			}
+			if r.LoadBalancer == nil {
+				r.LoadBalancer = lb
+			}
 		}
 	}
 
@@ -392,3 +409,31 @@ func (t *Translator) buildRateLimit(policy *egv1a1.BackendTrafficPolicy) *ir.Rat
 
 	return rateLimit
 }
+
+func (t *Translator) buildLoadBalancer(policy *egv1a1.BackendTrafficPolicy) *ir.LoadBalancer {
+	var lb *ir.LoadBalancer
+	switch policy.Spec.LoadBalancer.Type {
+	case egv1a1.ConsistentHashLoadBalancerType:
+		lb = &ir.LoadBalancer{
+			ConsistentHash: &ir.ConsistentHash{},
+		}
+		if policy.Spec.LoadBalancer.ConsistentHash != nil &&
+			policy.Spec.LoadBalancer.ConsistentHash.Type == egv1a1.SourceIPConsistentHashType {
+			lb.ConsistentHash.SourceIP = ptr.To(true)
+		}
+	case egv1a1.LeastRequestLoadBalancerType:
+		lb = &ir.LoadBalancer{
+			LeastRequest: &ir.LeastRequest{},
+		}
+	case egv1a1.RandomLoadBalancerType:
+		lb = &ir.LoadBalancer{
+			Random: &ir.Random{},
+		}
+	case egv1a1.RoundRobinLoadBalancerType:
+		lb = &ir.LoadBalancer{
+			RoundRobin: &ir.RoundRobin{},
+		}
+	}
+
+	return lb
+}

internal/gatewayapi/testdata/backendtrafficpolicy-with-loadbalancer.in.yaml

@@ -0,0 +1,93 @@
+gateways:
+- apiVersion: gateway.networking.k8s.io/v1
+  kind: Gateway
+  metadata:
+    namespace: envoy-gateway
+    name: gateway-1
+  spec:
+    gatewayClassName: envoy-gateway-class
+    listeners:
+    - name: http
+      protocol: HTTP
+      port: 80
+      allowedRoutes:
+        namespaces:
+          from: All
+- apiVersion: gateway.networking.k8s.io/v1
+  kind: Gateway
+  metadata:
+    namespace: envoy-gateway
+    name: gateway-2
+  spec:
+    gatewayClassName: envoy-gateway-class
+    listeners:
+    - name: http
+      protocol: HTTP
+      port: 80
+      allowedRoutes:
+        namespaces:
+          from: All
+grpcRoutes:
+- apiVersion: gateway.networking.k8s.io/v1alpha2
+  kind: GRPCRoute
+  metadata:
+    namespace: default
+    name: grpcroute-1
+  spec:
+    parentRefs:
+    - namespace: envoy-gateway
+      name: gateway-1
+      sectionName: http
+    rules:
+    - backendRefs:
+      - name: service-1
+        port: 8080
+httpRoutes:
+- apiVersion: gateway.networking.k8s.io/v1
+  kind: HTTPRoute
+  metadata:
+    namespace: default
+    name: httproute-1
+  spec:
+    hostnames:
+    - gateway.envoyproxy.io
+    parentRefs:
+    - namespace: envoy-gateway
+      name: gateway-2
+      sectionName: http
+    rules:
+    - matches:
+      - path:
+          value: "/"
+      backendRefs:
+      - name: service-1
+        port: 8080
+backendTrafficPolicies:
+- apiVersion: gateway.envoyproxy.io/v1alpha1
+  kind: BackendTrafficPolicy
+  metadata:
+    namespace: envoy-gateway
+    name: policy-for-gateway
+  spec:
+    targetRef:
+      group: gateway.networking.k8s.io
+      kind: Gateway
+      name: gateway-1
+      namespace: envoy-gateway
+    loadBalancer:
+      type: Random
+- apiVersion: gateway.envoyproxy.io/v1alpha1
+  kind: BackendTrafficPolicy
+  metadata:
+    namespace: default
+    name: policy-for-route
+  spec:
+    targetRef:
+      group: gateway.networking.k8s.io
+      kind: HTTPRoute
+      name: httproute-1
+      namespace: default
+    loadBalancer:
+      type: ConsistentHash
+      consistentHash:
+        type: SourceIP