open-consul/agent/xds/serverlessplugin/patcher.go

package serverlessplugin

import (
	envoy_cluster_v3 "github.com/envoyproxy/go-control-plane/envoy/config/cluster/v3"
	envoy_listener_v3 "github.com/envoyproxy/go-control-plane/envoy/config/listener/v3"
	envoy_route_v3 "github.com/envoyproxy/go-control-plane/envoy/config/route/v3"

	"github.com/hashicorp/consul/agent/xds/xdscommon"
	"github.com/hashicorp/consul/api"
)

// patcher is the interface that each serverless integration must implement. It
// is responsible for modifying the xDS structures based on only the state of
// the patcher.
type patcher interface {
	// CanPatch determines if the patcher can mutate resources for the given api.ServiceKind
	CanPatch(api.ServiceKind) bool

	// patchRoute patches a route to include the custom Envoy configuration
	// PatchCluster patches a cluster to include the custom Envoy configuration
	// required to integrate with the serverless integration.
	PatchRoute(*envoy_route_v3.RouteConfiguration) (*envoy_route_v3.RouteConfiguration, bool, error)

	// PatchCluster patches a cluster to include the custom Envoy configuration
	// required to integrate with the serverless integration.
	PatchCluster(*envoy_cluster_v3.Cluster) (*envoy_cluster_v3.Cluster, bool, error)

	// PatchFilter patches an Envoy filter to include the custom Envoy
	// configuration required to integrate with the serverless integration.
	PatchFilter(*envoy_listener_v3.Filter) (*envoy_listener_v3.Filter, bool, error)
}

type patchers map[api.CompoundServiceName]patcher

// getPatcherBySNI gets the patcher for the associated SNI.
func getPatcherBySNI(config xdscommon.PluginConfiguration, sni string) patcher {
	serviceName, ok := config.SNIToServiceName[sni]

	if !ok {
		return nil
	}

	serviceConfig, ok := config.ServiceConfigs[serviceName]
	if !ok {
		return nil
	}

	p := makePatcher(serviceConfig)
	if p == nil || !p.CanPatch(config.Kind) {
		return nil
	}

	return p
}

// getPatcherByEnvoyID gets the patcher for the associated envoy id.
func getPatcherByEnvoyID(config xdscommon.PluginConfiguration, envoyID string) patcher {
	serviceName, ok := config.EnvoyIDToServiceName[envoyID]

	if !ok {
		return nil
	}

	serviceConfig, ok := config.ServiceConfigs[serviceName]
	if !ok {
		return nil
	}

	p := makePatcher(serviceConfig)
	if p == nil || !p.CanPatch(config.Kind) {
		return nil
	}

	return p
}

func makePatcher(serviceConfig xdscommon.ServiceConfig) patcher {
	for _, constructor := range patchConstructors {
		patcher, ok := constructor(serviceConfig)
		if ok {
			return patcher
		}
	}

	return nil
}

// patchConstructor is used to construct patchers based on
// xdscommon.ServiceConfig. This function contains all of the logic around
// turning Meta data into the patcher.
type patchConstructor func(xdscommon.ServiceConfig) (patcher, bool)

// patchConstructors contains all patchers that getPatchers tries to create.
var patchConstructors = []patchConstructor{makeLambdaPatcher}