API for LoadBalancing Strategy in EnvoyProxy API

* Allows the user to configure a global load balancing strategy
for the envoy proxy data plane

```
apiVersion: config.gateway.envoyproxy.io/v1alpha1
kind: EnvoyProxy
metadata:
  name: set-lb-strategy
spec:
  traffic:
    loadBalancer:
      strategy: LeastRequest
```
* Sets the default load balancing strategy to `LeastRequest` which
will internally set the `WeightedLeastReqquest` knob in Envoy

* Relates to envoyproxy#1256 allowing
the user to fall back to `ClusterIP` style loadbalancing

* Relates to envoyproxy#1105

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

api/config/v1alpha1/envoyproxy_types.go

@@ -61,6 +61,9 @@ type EnvoyProxySpec struct {
 	//
 	// +optional
 	Bootstrap *string `json:"bootstrap,omitempty"`
+	// Traffic settings in the data plane.
+	// +optional
+	Traffic *EnvoyProxyTrafficSettings `json:"traffic,omitempty"`
 }
 
 // EnvoyProxyProvider defines the desired state of a resource provider.
@@ -164,6 +167,49 @@ const (
 	LogLevelError LogLevel = "error"
 )
 
+// EnvoyProxyTrafficSettings defines the traffic settings for requests being
+// processed by the EnvoyProxy data plane.
+type EnvoyProxyTrafficSettings struct {
+	// LoadBalancer defines the load balancer settings between
+	// the Envoy Proxy data plane and the upstream hosts.
+	//
+	// +optional
+	LoadBalancer *EnvoyProxyLoadBalancerSetting `json:"loadBalancer,omitempty"`
+}
+
+type EnvoyProxyLoadBalancerSetting struct {
+	// Strategy for load balancing.
+	//
+	// +kubebuilder:default=LeastRequest
+	Strategy LoadBalancerStrategy `json:"strategy,omitempty"`
+}
+
+// LoadBalancerStrategy defines the type of load balancing strategy to use.
+//
+// +kubebuilder:validation:Enum=LeastRequest;RoundRobin;Random;ClusterIP
+type LoadBalancerStrategy string
+
+const (
+	// LoadBalancerStrategyLeastRequest defines the "LeastRequest" load balancing strategy.
+	// In this mode, the upstream hosts is picked based on fewer active requests.
+	// Visit https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/upstream/load_balancing/load_balancers#weighted-least-request for more details.
+	LoadBalancerStrategyLeastRequest LoadBalancerStrategy = "LeastRequest"
+
+	// LoadBalancerStrategyRoundRobin defines the "RoundRobin" load balancing strategy.
+	// In this mode, the upstream host is selected in weighed round robin order.
+	// Visit https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/upstream/load_balancing/load_balancers#weighted-round-robin for more details.
+	LoadBalancerStrategyRoundRobin LoadBalancerStrategy = "RoundRobin"
+
+	// LoadBalancerStrategyRandom defines the "Random" load balancing strategy.
+	// In this mode, the upstream host is chosen randomly.
+	LoadBalancerStrategyRandom LoadBalancerStrategy = "Random"
+
+	// LoadBalancerStrategyClusterIP defines the "ClusterIP" load balancing strategy.
+	// In this mode, EnvoyProxy routes requests to the ClusterIP of the service and
+	// relies on another entity such as kube-proxy to perform load balancing to the upstream hosts.
+	LoadBalancerStrategyClusterIP LoadBalancerStrategy = "ClusterIP"
+)
+
 // EnvoyProxyStatus defines the observed state of EnvoyProxy. This type is not implemented
 // until https://github.com/envoyproxy/gateway/issues/1007 is fixed.
 type EnvoyProxyStatus struct {

charts/gateway-helm/crds/generated/config.gateway.envoyproxy.io_envoyproxies.yaml

@@ -3836,6 +3836,24 @@ spec:
                 required:
                 - type
                 type: object
+              traffic:
+                description: Traffic settings in the data plane.
+                properties:
+                  loadBalancer:
+                    description: LoadBalancer defines the load balancer settings between
+                      the Envoy Proxy data plane and the upstream hosts.
+                    properties:
+                      strategy:
+                        default: LeastRequest
+                        description: Strategy for load balancing.
+                        enum:
+                        - LeastRequest
+                        - RoundRobin
+                        - Random
+                        - ClusterIP
+                        type: string
+                    type: object
+                type: object
             type: object
           status:
             description: EnvoyProxyStatus defines the actual state of EnvoyProxy.

docs/latest/api/config_types.md

@@ -185,6 +185,20 @@ _Appears in:_
 | `envoyService` _[KubernetesServiceSpec](#kubernetesservicespec)_ | EnvoyService defines the desired state of the Envoy service resource. If unspecified, default settings for the manged Envoy service resource are applied. |
 
 
+## EnvoyProxyLoadBalancerSetting
+
+
+
+
+
+_Appears in:_
+- [EnvoyProxyTrafficSettings](#envoyproxytrafficsettings)
+
+| Field | Description |
+| --- | --- |
+| `strategy` _[LoadBalancerStrategy](#loadbalancerstrategy)_ | Strategy for load balancing. |
+
+
 ## EnvoyProxyProvider
 
 
@@ -215,9 +229,24 @@ _Appears in:_
 | `logging` _[ProxyLogging](#proxylogging)_ | Logging defines logging parameters for managed proxies. If unspecified, default settings apply. This type is not implemented until https://github.com/envoyproxy/gateway/issues/280 is fixed. |
 | `accessLoggings` _[ProxyAccessLogging](#proxyaccesslogging) array_ | AccessLoggings defines access logging parameters for managed proxies. If unspecified, access log is disabled. |
 | `bootstrap` _string_ | Bootstrap defines the Envoy Bootstrap as a YAML string. Visit https://www.envoyproxy.io/docs/envoy/latest/api-v3/config/bootstrap/v3/bootstrap.proto#envoy-v3-api-msg-config-bootstrap-v3-bootstrap to learn more about the syntax. If set, this is the Bootstrap configuration used for the managed Envoy Proxy fleet instead of the default Bootstrap configuration set by Envoy Gateway. Some fields within the Bootstrap that are required to communicate with the xDS Server (Envoy Gateway) and receive xDS resources from it are not configurable and will result in the `EnvoyProxy` resource being rejected. Backward compatibility across minor versions is not guaranteed. We strongly recommend using `egctl x translate` to generate a `EnvoyProxy` resource with the `Bootstrap` field set to the default Bootstrap configuration used. You can edit this configuration, and rerun `egctl x translate` to ensure there are no validation errors. |
+| `traffic` _[EnvoyProxyTrafficSettings](#envoyproxytrafficsettings)_ | Traffic settings in the data plane. |
+
+
+
+
+## EnvoyProxyTrafficSettings
 
 
 
+EnvoyProxyTrafficSettings defines the traffic settings for requests being processed by the EnvoyProxy data plane.
+
+_Appears in:_
+- [EnvoyProxySpec](#envoyproxyspec)
+
+| Field | Description |
+| --- | --- |
+| `loadBalancer` _[EnvoyProxyLoadBalancerSetting](#envoyproxyloadbalancersetting)_ | LoadBalancer defines the load balancer settings between the Envoy Proxy data plane and the upstream hosts. |
+
 
 ## Extension
 
@@ -430,6 +459,17 @@ _Appears in:_
 | `Namespaces` _string array_ | Namespaces holds the list of namespaces that Envoy Gateway will watch for namespaced scoped resources such as Gateway, HTTPRoute and Service. Note that Envoy Gateway will continue to reconcile relevant cluster scoped resources such as GatewayClass that it is linked to. By default, when this field is unset or empty, Envoy Gateway will watch for input namespaced resources from all namespaces. |
 
 
+## LoadBalancerStrategy
+
+_Underlying type:_ `string`
+
+LoadBalancerStrategy defines the type of load balancing strategy to use.
+
+_Appears in:_
+- [EnvoyProxyLoadBalancerSetting](#envoyproxyloadbalancersetting)
+
+
+
 ## LogComponent
 
 _Underlying type:_ `string`