Add support for RequestMirror filter

Problem: As a user, I want to be able to mirror requests to another backend(s) using the RequestMirror filter on an HTTPRoute or GRPCRoute.

Solution: Add support for the RequestMirror filter, allowing users to mirror requests with HTTPRoutes or GRPCRoutes.

Author: sjberman

Diff for: internal/mode/static/nginx/config/http/config.go

@@ -5,8 +5,9 @@ import (
 )
 
 const (
-	InternalRoutePathPrefix = "/_ngf-internal"
-	HTTPSScheme             = "https"
+	InternalRoutePathPrefix       = "/_ngf-internal"
+	InternalMirrorRoutePathPrefix = InternalRoutePathPrefix + "-mirror"
+	HTTPSScheme                   = "https"
 )
 
 // Server holds all configuration for an HTTP server.
@@ -41,6 +42,7 @@ type Location struct {
 	Return          *Return
 	ResponseHeaders ResponseHeaders
 	Rewrites        []string
+	MirrorPaths     []string
 	Includes        []shared.Include
 	GRPC            bool
 }

Diff for: internal/mode/static/nginx/config/servers.go

@@ -237,7 +237,7 @@ func createLocations(
 	matchPairs := make(httpMatchPairs)
 
 	var rootPathExists bool
-	var grpc bool
+	var grpcServer bool
 
 	for pathRuleIdx, rule := range server.PathRules {
 		matches := make([]routeMatch, 0, len(rule.MatchRules))
@@ -247,7 +247,7 @@ func createLocations(
 		}
 
 		if rule.GRPC {
-			grpc = true
+			grpcServer = true
 		}
 
 		extLocations := initializeExternalLocations(rule, pathsAndTypes)
@@ -277,7 +277,7 @@ func createLocations(
 		internalLocations := make([]http.Location, 0, len(rule.MatchRules))
 
 		for matchRuleIdx, r := range rule.MatchRules {
-			intLocation, match := initializeInternalLocation(pathRuleIdx, matchRuleIdx, r.Match, grpc)
+			intLocation, match := initializeInternalLocation(pathRuleIdx, matchRuleIdx, r.Match, rule.GRPC)
 			intLocation.Includes = createIncludesFromPolicyGenerateResult(
 				generator.GenerateForInternalLocation(rule.Policies),
 			)
@@ -313,7 +313,7 @@ func createLocations(
 		locs = append(locs, createDefaultRootLocation())
 	}
 
-	return locs, matchPairs, grpc
+	return locs, matchPairs, grpcServer
 }
 
 func needsInternalLocations(rule dataplane.PathRule) bool {
@@ -433,6 +433,13 @@ func updateLocation(
 		return location
 	}
 
+	if strings.HasPrefix(path, http.InternalMirrorRoutePathPrefix) {
+		location.Type = http.InternalLocationType
+		if grpc {
+			location.Rewrites = []string{"^ $request_uri break"}
+		}
+	}
+
 	location.Includes = append(location.Includes, createIncludesFromLocationSnippetsFilters(filters.SnippetsFilters)...)
 
 	if filters.RequestRedirect != nil {
@@ -445,6 +452,20 @@ func updateLocation(
 	}
 
 	rewrites := createRewritesValForRewriteFilter(filters.RequestURLRewrite, path)
+	if rewrites != nil {
+		if location.Type == http.InternalLocationType && rewrites.InternalRewrite != "" {
+			location.Rewrites = append(location.Rewrites, rewrites.InternalRewrite)
+		}
+		if rewrites.MainRewrite != "" {
+			location.Rewrites = append(location.Rewrites, rewrites.MainRewrite)
+		}
+	}
+
+	for _, filter := range filters.RequestMirrors {
+		if filter.Target != nil {
+			location.MirrorPaths = append(location.MirrorPaths, *filter.Target)
+		}
+	}
 
 	extraHeaders := make([]http.Header, 0, 3)
 	if grpc {
@@ -457,15 +478,6 @@ func updateLocation(
 	proxySetHeaders := generateProxySetHeaders(&matchRule.Filters, createBaseProxySetHeaders(extraHeaders...))
 	responseHeaders := generateResponseHeaders(&matchRule.Filters)
 
-	if rewrites != nil {
-		if location.Type == http.InternalLocationType && rewrites.InternalRewrite != "" {
-			location.Rewrites = append(location.Rewrites, rewrites.InternalRewrite)
-		}
-		if rewrites.MainRewrite != "" {
-			location.Rewrites = append(location.Rewrites, rewrites.MainRewrite)
-		}
-	}
-
 	location.ProxySetHeaders = proxySetHeaders
 	location.ProxySSLVerify = createProxyTLSFromBackends(matchRule.BackendGroup.Backends)
 	proxyPass := createProxyPass(
@@ -740,6 +752,7 @@ func isPathOnlyMatch(match dataplane.Match) bool {
 	return match.Method == nil && len(match.Headers) == 0 && len(match.QueryParams) == 0
 }
 
+// TODO(sberman): if this is an internal mirror location, don't set request_uri (test this).
 func createProxyPass(
 	backendGroup dataplane.BackendGroup,
 	filter *dataplane.HTTPURLRewriteFilter,

Diff for: internal/mode/static/nginx/config/servers_template.go

@@ -101,6 +101,10 @@ server {
         rewrite {{ $r }};
         {{- end }}
 
+        {{- range $m := $l.MirrorPaths }}
+        mirror {{ $m }};
+        {{- end }}
+
         {{- if $l.Return }}
         return {{ $l.Return.Code }} "{{ $l.Return.Body }}";
         {{- end }}

Diff for: internal/mode/static/nginx/config/servers_test.go

@@ -7,6 +7,7 @@ import (
 	"testing"
 
 	. "github.com/onsi/gomega"
+	"github.com/onsi/gomega/format"
 	"k8s.io/apimachinery/pkg/types"
 
 	"github.com/nginx/nginx-gateway-fabric/internal/framework/helpers"
@@ -862,6 +863,66 @@ func TestCreateServers(t *testing.T) {
 				},
 			},
 		},
+		{
+			Path:     "/mirror",
+			PathType: dataplane.PathTypePrefix,
+			MatchRules: []dataplane.MatchRule{
+				{
+					Match: dataplane.Match{},
+					Filters: dataplane.HTTPFilters{
+						RequestMirrors: []*dataplane.HTTPRequestMirrorFilter{
+							{
+								Name:      helpers.GetPointer("mirror-filter"),
+								Namespace: helpers.GetPointer("test-ns"),
+								Target:    helpers.GetPointer(http.InternalMirrorRoutePathPrefix + "-my-backend"),
+							},
+						},
+					},
+					BackendGroup: fooGroup,
+				},
+			},
+		},
+		{
+			Path:     http.InternalMirrorRoutePathPrefix + "-my-backend",
+			PathType: dataplane.PathTypeExact,
+			MatchRules: []dataplane.MatchRule{
+				{
+					Match:        dataplane.Match{},
+					BackendGroup: fooGroup,
+				},
+			},
+		},
+		{
+			Path:     "/grpc/mirror",
+			PathType: dataplane.PathTypeExact,
+			MatchRules: []dataplane.MatchRule{
+				{
+					Match: dataplane.Match{},
+					Filters: dataplane.HTTPFilters{
+						RequestMirrors: []*dataplane.HTTPRequestMirrorFilter{
+							{
+								Name:      helpers.GetPointer("grpc-mirror-filter"),
+								Namespace: helpers.GetPointer("test-ns"),
+								Target:    helpers.GetPointer(http.InternalMirrorRoutePathPrefix + "-my-grpc-backend"),
+							},
+						},
+					},
+					BackendGroup: fooGroup,
+				},
+			},
+			GRPC: true,
+		},
+		{
+			Path:     http.InternalMirrorRoutePathPrefix + "-my-grpc-backend",
+			PathType: dataplane.PathTypeExact,
+			MatchRules: []dataplane.MatchRule{
+				{
+					Match:        dataplane.Match{},
+					BackendGroup: fooGroup,
+				},
+			},
+			GRPC: true,
+		},
 		{
 			Path:     "/invalid-filter",
 			PathType: dataplane.PathTypePrefix,
@@ -1093,25 +1154,25 @@ func TestCreateServers(t *testing.T) {
 				RedirectPath: "/_ngf-internal-rule8-route0",
 			},
 		},
-		"1_10": {
+		"1_14": {
 			{
 				Headers:      []string{"filter:Exact:this"},
-				RedirectPath: "/_ngf-internal-rule10-route0",
+				RedirectPath: "/_ngf-internal-rule14-route0",
 			},
 		},
-		"1_12": {
+		"1_16": {
 			{
 				Method:       "GET",
-				RedirectPath: "/_ngf-internal-rule12-route0",
+				RedirectPath: "/_ngf-internal-rule16-route0",
 				Headers:      nil,
 				QueryParams:  nil,
 				Any:          false,
 			},
 		},
-		"1_17": {
+		"1_21": {
 			{
 				Method:       "GET",
-				RedirectPath: "/_ngf-internal-rule17-route0",
+				RedirectPath: "/_ngf-internal-rule21-route0",
 			},
 		},
 	}
@@ -1342,6 +1403,47 @@ func TestCreateServers(t *testing.T) {
 				Type:            http.InternalLocationType,
 				Includes:        internalIncludes,
 			},
+			{
+				Path:            "/mirror/",
+				ProxyPass:       "http://test_foo_80$request_uri",
+				ProxySetHeaders: httpBaseHeaders,
+				MirrorPaths:     []string{"/_ngf-internal-mirror-my-backend"},
+				Type:            http.ExternalLocationType,
+				Includes:        externalIncludes,
+			},
+			{
+				Path:            "= /mirror",
+				ProxyPass:       "http://test_foo_80$request_uri",
+				ProxySetHeaders: httpBaseHeaders,
+				MirrorPaths:     []string{"/_ngf-internal-mirror-my-backend"},
+				Type:            http.ExternalLocationType,
+				Includes:        externalIncludes,
+			},
+			{
+				Path:            "= /_ngf-internal-mirror-my-backend",
+				ProxyPass:       "http://test_foo_80$request_uri",
+				ProxySetHeaders: httpBaseHeaders,
+				Type:            http.InternalLocationType,
+				Includes:        externalIncludes,
+			},
+			{
+				Path:            "= /grpc/mirror",
+				GRPC:            true,
+				ProxyPass:       "grpc://test_foo_80",
+				ProxySetHeaders: grpcBaseHeaders,
+				MirrorPaths:     []string{"/_ngf-internal-mirror-my-grpc-backend"},
+				Type:            http.ExternalLocationType,
+				Includes:        externalIncludes,
+			},
+			{
+				Path:            "= /_ngf-internal-mirror-my-grpc-backend",
+				GRPC:            true,
+				ProxyPass:       "grpc://test_foo_80",
+				Rewrites:        []string{"^ $request_uri break"},
+				ProxySetHeaders: grpcBaseHeaders,
+				Type:            http.InternalLocationType,
+				Includes:        externalIncludes,
+			},
 			{
 				Path: "/invalid-filter/",
 				Return: &http.Return{
@@ -1360,18 +1462,18 @@ func TestCreateServers(t *testing.T) {
 			},
 			{
 				Path:         "/invalid-filter-with-headers/",
-				HTTPMatchKey: ssl + "1_10",
+				HTTPMatchKey: ssl + "1_14",
 				Type:         http.RedirectLocationType,
 				Includes:     externalIncludes,
 			},
 			{
 				Path:         "= /invalid-filter-with-headers",
-				HTTPMatchKey: ssl + "1_10",
+				HTTPMatchKey: ssl + "1_14",
 				Type:         http.RedirectLocationType,
 				Includes:     externalIncludes,
 			},
 			{
-				Path: "/_ngf-internal-rule10-route0",
+				Path: "/_ngf-internal-rule14-route0",
 				Return: &http.Return{
 					Code: http.StatusInternalServerError,
 				},
@@ -1387,12 +1489,12 @@ func TestCreateServers(t *testing.T) {
 			},
 			{
 				Path:         "= /test",
-				HTTPMatchKey: ssl + "1_12",
+				HTTPMatchKey: ssl + "1_16",
 				Type:         http.RedirectLocationType,
 				Includes:     externalIncludes,
 			},
 			{
-				Path:            "/_ngf-internal-rule12-route0",
+				Path:            "/_ngf-internal-rule16-route0",
 				ProxyPass:       "http://test_foo_80$request_uri",
 				ProxySetHeaders: httpBaseHeaders,
 				Type:            http.InternalLocationType,
@@ -1471,15 +1573,14 @@ func TestCreateServers(t *testing.T) {
 			},
 			{
 				Path:         "= /include-header-match",
-				HTTPMatchKey: ssl + "1_17",
+				HTTPMatchKey: ssl + "1_21",
 				Type:         http.RedirectLocationType,
 				Includes:     externalIncludes,
 			},
 			{
-				Path:            "/_ngf-internal-rule17-route0",
+				Path:            "/_ngf-internal-rule21-route0",
 				ProxyPass:       "http://test_foo_80$request_uri",
 				ProxySetHeaders: httpBaseHeaders,
-				Rewrites:        []string{"^ $request_uri break"},
 				Type:            http.InternalLocationType,
 				Includes:        internalIncludes,
 			},
@@ -1572,6 +1673,7 @@ func TestCreateServers(t *testing.T) {
 
 	result, httpMatchPair := createServers(conf, fakeGenerator, keepAliveCheck)
 
+	format.MaxLength = 10000
 	g.Expect(httpMatchPair).To(Equal(allExpMatchPair))
 	g.Expect(helpers.Diff(expectedServers, result)).To(BeEmpty())
 }

Diff for: internal/mode/static/nginx/config/validation/http_validator.go

@@ -15,4 +15,6 @@ type HTTPValidator struct {
 	HTTPPathValidator
 }
 
+func (HTTPValidator) SkipValidation() bool { return false }
+
 var _ validation.HTTPFieldsValidator = HTTPValidator{}