implement direct response

config/constants.go

@@ -20,7 +20,7 @@ var (
 	errHostnameMustBeSpecified              = errors.New("endpoint hostname must be specified")
 	errSchemeMustBeSpecified                = errors.New("url scheme must be provided")
 	errEmptyUrls                            = errors.New("url list is empty")
-	errEitherToOrRedirectRequired = errors.New("policy should have either `to` or `redirect` defined")
+	errEitherToOrRedirectOrResponseRequired = errors.New("policy should have either `to` or `redirect` or `response` defined")
 )
 
 var protoPartial = protojson.UnmarshalOptions{AllowPartial: true, DiscardUnknown: true}

config/envoyconfig/routes.go

@@ -282,6 +282,9 @@ func (b *Builder) buildRouteForPolicyAndMatch(
 			return nil, err
 		}
 		route.Action = &envoy_config_route_v3.Route_Redirect{Redirect: action}
+	} else if policy.Response != nil {
+		action := b.buildPolicyRouteDirectResponseAction(policy.Response)
+		route.Action = &envoy_config_route_v3.Route_DirectResponse{DirectResponse: action}
 	} else {
 		action, err := b.buildPolicyRouteRouteAction(cfg.Options, policy)
 		if err != nil {
@@ -343,6 +346,17 @@ func (b *Builder) buildRouteForPolicyAndMatch(
 	return route, nil
 }
 
+func (b *Builder) buildPolicyRouteDirectResponseAction(r *config.DirectResponse) *envoy_config_route_v3.DirectResponseAction {
+	return &envoy_config_route_v3.DirectResponseAction{
+		Status: uint32(r.Status),
+		Body: &envoy_config_core_v3.DataSource{
+			Specifier: &envoy_config_core_v3.DataSource_InlineString{
+				InlineString: r.Body,
+			},
+		},
+	}
+}
+
 func (b *Builder) buildPolicyRouteRedirectAction(r *config.PolicyRedirect) (*envoy_config_route_v3.RedirectAction, error) {
 	action := &envoy_config_route_v3.RedirectAction{}
 	switch {

config/policy.go

@@ -30,6 +30,7 @@ type Policy struct {
 
 	From     string          `mapstructure:"from" yaml:"from"`
 	To       WeightedURLs    `mapstructure:"to" yaml:"to"`
+	Response *DirectResponse `mapstructure:"response" yaml:"response,omitempty" json:"response,omitempty"`
 
 	// LbWeights are optional load balancing weights applied to endpoints specified in To
 	// this field exists for compatibility with mapstructure
@@ -213,6 +214,12 @@ type PolicyRedirect struct {
 	StripQuery     *bool   `mapstructure:"strip_query" yaml:"strip_query,omitempty" json:"strip_query,omitempty"`
 }
 
+// A DirectResponse is the response to an HTTP request.
+type DirectResponse struct {
+	Status int    `mapstructure:"status" yaml:"status,omitempty" json:"status,omitempty"`
+	Body   string `mapstructure:"body" yaml:"body,omitempty" json:"body,omitempty"`
+}
+
 // NewPolicyFromProto creates a new Policy from a protobuf policy config route.
 func NewPolicyFromProto(pb *configpb.Route) (*Policy, error) {
 	var timeout *time.Duration
@@ -446,8 +453,8 @@ func (p *Policy) Validate() error {
 			source.String())
 	}
 
-	if len(p.To) == 0 && p.Redirect == nil {
+	if len(p.To) == 0 && p.Redirect == nil && p.Response == nil {
-		return errEitherToOrRedirectRequired
+		return errEitherToOrRedirectOrResponseRequired
 	}
 
 	for _, u := range p.To {
@@ -567,8 +574,11 @@ func (p *Policy) RouteID() (uint64, error) {
 		id.To = dst
 	} else if p.Redirect != nil {
 		id.Redirect = p.Redirect
+	} else if p.Response != nil {
+		id.DirectResponseStatus = p.Response.Status
+		id.DirectResponseBody = p.Response.Body
 	} else {
-		return 0, errEitherToOrRedirectRequired
+		return 0, errEitherToOrRedirectOrResponseRequired
 	}
 
 	return hashutil.Hash(id)
@@ -685,6 +695,8 @@ type routeID struct {
 	Path                 string
 	Regex                string
 	Redirect             *PolicyRedirect
+	DirectResponseStatus int
+	DirectResponseBody   string
 }
 
 /*

pkg/grpc/config/config.proto

@@ -33,12 +33,18 @@ message RouteRedirect {
   optional bool strip_query = 8;
 }
 
-// Next ID: 62.
+message RouteDirectResponse {
+  uint32 status = 1;
+  string body = 2;
+}
+
+// Next ID: 63.
 message Route {
   string name = 1;
 
   string from = 2;
   repeated string to = 3;
+  RouteDirectResponse response = 62;
 
   // https://www.envoyproxy.io/docs/envoy/latest/api-v3/config/endpoint/v3/endpoint_components.proto#envoy-v3-api-msg-config-endpoint-v3-lbendpoint
   // optional load balancing weights assigned to upstream servers defined in TO