add support for http header routing

Signed-off-by: Justin Reasoner <gjreasoner@gmail.com>

Author: gjreasoner

interceptor/config/serving.go

@@ -45,6 +45,9 @@ type Serving struct {
 	TLSCertStorePaths string `envconfig:"KEDA_HTTP_PROXY_TLS_CERT_STORE_PATHS" default:""`
 	// TLSPort is the port that the server should serve on if TLS is enabled
 	TLSPort int `envconfig:"KEDA_HTTP_PROXY_TLS_PORT" default:"8443"`
+	// RoutingHeader is an optional header that can be used to route requests
+	// to different backends when set and sent in the HTTP request
+	RoutingHeader string `envconfig:"KEDA_HTTP_ROUTING_HEADER" default:""`
 }
 
 // Parse parses standard configs using envconfig and returns a pointer to the

interceptor/handler/static.go

@@ -31,7 +31,7 @@ func (sh *Static) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	stream := util.StreamFromContext(ctx)
 
 	statusText := http.StatusText(sh.statusCode)
-	routingKey := routing.NewKeyFromRequest(r)
+	routingKey := routing.NewKeyFromRequest(r, "")
 	namespacedName := k8s.NamespacedNameFromObject(httpso)
 	logger.Error(sh.err, statusText, "routingKey", routingKey, "namespacedName", namespacedName, "stream", stream)
 

interceptor/handler/static_test.go

@@ -23,6 +23,8 @@ var _ = Describe("ServeHTTP", func() {
 		st = http.StatusText(sc)
 
 		se = errors.New("test error")
+
+		rh = ""
 	)
 
 	BeforeEach(func() {
@@ -47,7 +49,7 @@ var _ = Describe("ServeHTTP", func() {
 				err := json.Unmarshal([]byte(obj), &m)
 				Expect(err).NotTo(HaveOccurred())
 
-				rk := routing.NewKeyFromRequest(r)
+				rk := routing.NewKeyFromRequest(r, rh)
 				Expect(m).To(HaveKeyWithValue("error", se.Error()))
 				Expect(m).To(HaveKeyWithValue("msg", st))
 				Expect(m).To(HaveKeyWithValue("routingKey", rk.String()))

interceptor/main.go

@@ -106,7 +106,7 @@ func main() {
 	queues := queue.NewMemory()
 
 	sharedInformerFactory := informers.NewSharedInformerFactory(httpCl, servingCfg.ConfigMapCacheRsyncPeriod)
-	routingTable, err := routing.NewTable(sharedInformerFactory, servingCfg.WatchNamespace, queues)
+	routingTable, err := routing.NewTable(sharedInformerFactory, servingCfg.WatchNamespace, queues, servingCfg.RoutingHeader)
 	if err != nil {
 		setupLog.Error(err, "fetching routing table")
 		os.Exit(1)

pkg/routing/key.go

@@ -33,7 +33,7 @@ func NewKeyFromURL(url *url.URL) Key {
 	return NewKey(url.Host, url.Path)
 }
 
-func NewKeyFromRequest(req *http.Request) Key {
+func NewKeyFromRequest(req *http.Request, httpRoutingHeaderKey string) Key {
 	if req == nil {
 		return nil
 	}
@@ -48,6 +48,12 @@ func NewKeyFromRequest(req *http.Request) Key {
 		keyURL.Host = reqHost
 	}
 
+	if httpRoutingHeaderKey != "" {
+		if httpRoutingHeaderValue := req.Header.Get(httpRoutingHeaderKey); httpRoutingHeaderValue != "" {
+			keyURL.Host = httpRoutingHeaderValue
+		}
+	}
+
 	return NewKeyFromURL(&keyURL)
 }
 

pkg/routing/key_test.go

@@ -2,13 +2,11 @@ package routing
 
 import (
 	"fmt"
-	"net/http"
-	"net/url"
-
+	httpv1alpha1 "github.com/kedacore/http-add-on/operator/apis/http/v1alpha1"
 	. "github.com/onsi/ginkgo/v2"
 	. "github.com/onsi/gomega"
-
-	httpv1alpha1 "github.com/kedacore/http-add-on/operator/apis/http/v1alpha1"
+	"net/http"
+	"net/url"
 )
 
 var _ = Describe("Key", func() {
@@ -125,23 +123,36 @@ var _ = Describe("Key", func() {
 	})
 
 	Context("NewFromRequest", func() {
+		const (
+			host          = "kubernetes.io"
+			path          = "abc/def"
+			norm0         = "//kubernetes.io/abc/def/"
+			norm1         = "//get-thing/abc/def/"
+			serviceHeader = "x-service-action-a"
+			serviceHost   = "get-thing"
+		)
+
 		It("returns expected key for Request", func() {
-			const (
-				host = "kubernetes.io"
-				path = "abc/def"
-				norm = "//kubernetes.io/abc/def/"
-			)
+			r, err := http.NewRequest("GET", fmt.Sprintf("https://%s:443/%s?123=456#789", host, path), nil)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(r).NotTo(BeNil())
+
+			key := NewKeyFromRequest(r, "")
+			Expect(key).To(Equal(Key(norm0)))
+		})
 
+		It("returns service host for Request with http routing header", func() {
 			r, err := http.NewRequest("GET", fmt.Sprintf("https://%s:443/%s?123=456#789", host, path), nil)
 			Expect(err).NotTo(HaveOccurred())
 			Expect(r).NotTo(BeNil())
+			r.Header.Set(serviceHeader, serviceHost)
 
-			key := NewKeyFromRequest(r)
-			Expect(key).To(Equal(Key(norm)))
+			key := NewKeyFromRequest(r, serviceHeader)
+			Expect(key).To(Equal(Key(norm1)))
 		})
 
 		It("returns nil for nil Request", func() {
-			key := NewKeyFromRequest(nil)
+			key := NewKeyFromRequest(nil, "")
 			Expect(key).To(BeNil())
 		})
 	})

pkg/routing/table.go

@@ -42,14 +42,16 @@ type table struct {
 	memoryHolder                             util.AtomicValue[TableMemory]
 	memorySignaler                           util.Signaler
 	queueCounter                             queue.Counter
+	routingHeader                            string
 }
 
-func NewTable(sharedInformerFactory externalversions.SharedInformerFactory, namespace string, counter queue.Counter) (Table, error) {
+func NewTable(sharedInformerFactory externalversions.SharedInformerFactory, namespace string, counter queue.Counter, routingHeader string) (Table, error) {
 	httpScaledObjects := informershttpv1alpha1.New(sharedInformerFactory, namespace, nil).HTTPScaledObjects()
 
 	t := table{
 		httpScaledObjects: make(map[types.NamespacedName]*httpv1alpha1.HTTPScaledObject),
 		memorySignaler:    util.NewSignaler(),
+		routingHeader:     routingHeader,
 	}
 
 	informer, ok := httpScaledObjects.Informer().(sharedIndexInformer)
@@ -134,7 +136,7 @@ func (t *table) Route(req *http.Request) *httpv1alpha1.HTTPScaledObject {
 		return nil
 	}
 
-	key := NewKeyFromRequest(req)
+	key := NewKeyFromRequest(req, t.routingHeader)
 	return tm.Route(key)
 }
 

pkg/routing/table_test.go

@@ -22,7 +22,8 @@ import (
 
 var _ = Describe("Table", func() {
 	const (
-		namespace = "default"
+		namespace     = "default"
+		routingHeader = "X-HTTP-Routing"
 	)
 
 	var (
@@ -111,7 +112,7 @@ var _ = Describe("Table", func() {
 
 	Context("New", func() {
 		It("returns a table with fields initialized", func() {
-			i, err := NewTable(sharedInformerFactory, namespace, queue.NewFakeCounter())
+			i, err := NewTable(sharedInformerFactory, namespace, queue.NewFakeCounter(), routingHeader)
 			Expect(err).NotTo(HaveOccurred())
 			Expect(i).NotTo(BeNil())
 
@@ -136,7 +137,7 @@ var _ = Describe("Table", func() {
 		)
 
 		BeforeEach(func() {
-			i, _ := NewTable(sharedInformerFactory, namespace, queue.NewFakeCounter())
+			i, _ := NewTable(sharedInformerFactory, namespace, queue.NewFakeCounter(), routingHeader)
 			t = i.(*table)
 		})
 
@@ -181,7 +182,7 @@ var _ = Describe("Table", func() {
 		)
 
 		BeforeEach(func() {
-			i, _ := NewTable(sharedInformerFactory, namespace, queue.NewFakeCounter())
+			i, _ := NewTable(sharedInformerFactory, namespace, queue.NewFakeCounter(), routingHeader)
 			t = i.(*table)
 		})
 
@@ -279,7 +280,7 @@ var _ = Describe("Table", func() {
 		)
 
 		BeforeEach(func() {
-			i, _ := NewTable(sharedInformerFactory, namespace, queue.NewFakeCounter())
+			i, _ := NewTable(sharedInformerFactory, namespace, queue.NewFakeCounter(), routingHeader)
 			t = i.(*table)
 		})