add header-value annotation

add new annotation (header-value)
parse it and propogate to lua script
alter balancer rule to include it into the canary routing logic
add e2e test to validate fallback for canary-by-header-value
add description of canary-by-header-value to documentation

internal/ingress/annotations/canary/main.go

@@ -30,10 +30,11 @@ type canary struct {
 
 // Config returns the configuration rules for setting up the Canary
 type Config struct {
-	Enabled bool
-	Weight  int
-	Header  string
-	Cookie  string
+	Enabled     bool
+	Weight      int
+	Header      string
+	HeaderValue string
+	Cookie      string
 }
 
 // NewParser parses the ingress for canary related annotations
@@ -62,12 +63,17 @@ func (c canary) Parse(ing *extensions.Ingress) (interface{}, error) {
 		config.Header = ""
 	}
 
+	config.HeaderValue, err = parser.GetStringAnnotation("canary-by-header-value", ing)
+	if err != nil {
+		config.HeaderValue = ""
+	}
+
 	config.Cookie, err = parser.GetStringAnnotation("canary-by-cookie", ing)
 	if err != nil {
 		config.Cookie = ""
 	}
 
-	if !config.Enabled && (config.Weight > 0 || len(config.Header) > 0 || len(config.Cookie) > 0) {
+	if !config.Enabled && (config.Weight > 0 || len(config.Header) > 0 || len(config.HeaderValue) > 0 || len(config.Cookie) > 0) {
 		return nil, errors.NewInvalidAnnotationConfiguration("canary", "configured but not enabled")
 	}
 

internal/ingress/controller/controller.go

@@ -690,9 +690,10 @@ func (n *NGINXController) createUpstreams(data []*ingress.Ingress, du *ingress.B
 			if anns.Canary.Enabled {
 				upstreams[defBackend].NoServer = true
 				upstreams[defBackend].TrafficShapingPolicy = ingress.TrafficShapingPolicy{
-					Weight: anns.Canary.Weight,
-					Header: anns.Canary.Header,
-					Cookie: anns.Canary.Cookie,
+					Weight:      anns.Canary.Weight,
+					Header:      anns.Canary.Header,
+					HeaderValue: anns.Canary.HeaderValue,
+					Cookie:      anns.Canary.Cookie,
 				}
 			}
 
@@ -757,9 +758,10 @@ func (n *NGINXController) createUpstreams(data []*ingress.Ingress, du *ingress.B
 				if anns.Canary.Enabled {
 					upstreams[name].NoServer = true
 					upstreams[name].TrafficShapingPolicy = ingress.TrafficShapingPolicy{
-						Weight: anns.Canary.Weight,
-						Header: anns.Canary.Header,
-						Cookie: anns.Canary.Cookie,
+						Weight:      anns.Canary.Weight,
+						Header:      anns.Canary.Header,
+						HeaderValue: anns.Canary.HeaderValue,
+						Cookie:      anns.Canary.Cookie,
 					}
 				}
 

internal/ingress/types.go

@@ -118,6 +118,8 @@ type TrafficShapingPolicy struct {
 	Weight int `json:"weight"`
 	// Header on which to redirect requests to this backend
 	Header string `json:"header"`
+	// HeaderValue on which to redirect requests to this backend
+	HeaderValue string `json:"headerValue"`
 	// Cookie on which to redirect requests to this backend
 	Cookie string `json:"cookie"`
 }

internal/ingress/types_equals.go

@@ -293,6 +293,9 @@ func (tsp1 TrafficShapingPolicy) Equal(tsp2 TrafficShapingPolicy) bool {
 	if tsp1.Header != tsp2.Header {
 		return false
 	}
+	if tsp1.HeaderValue != tsp2.HeaderValue {
+		return false
+	}
 	if tsp1.Cookie != tsp2.Cookie {
 		return false
 	}