Bugfix: non-host canary ingress use default server name as host to merge

internal/ingress/controller/controller.go

@@ -1369,6 +1369,11 @@ func mergeAlternativeBackends(ing *ingress.Ingress, upstreams map[string]*ingres
 	}
 
 	for _, rule := range ing.Spec.Rules {
+		host := rule.Host
+		if host == "" {
+			host = defServerName
+		}
+
 		for _, path := range rule.HTTP.Paths {
 			upsName := upstreamName(ing.Namespace, path.Backend.ServiceName, path.Backend.ServicePort)
 
@@ -1382,11 +1387,11 @@ func mergeAlternativeBackends(ing *ingress.Ingress, upstreams map[string]*ingres
 			merged := false
 			altEqualsPri := false
 
-			server, ok := servers[rule.Host]
+			server, ok := servers[host]
 			if !ok {
 				klog.Errorf("cannot merge alternative backend %s into hostname %s that does not exist",
 					altUps.Name,
-					rule.Host)
+					host)
 
 				continue
 			}

internal/ingress/controller/controller_test.go

@@ -694,6 +694,88 @@ func TestMergeAlternativeBackends(t *testing.T) {
 				},
 			},
 		},
+		"non-host canary ingress use default server name as host to merge": {
+			&ingress.Ingress{
+				Ingress: networking.Ingress{
+					ObjectMeta: metav1.ObjectMeta{
+						Namespace: "example",
+					},
+					Spec: networking.IngressSpec{
+						Rules: []networking.IngressRule{
+							{
+								IngressRuleValue: networking.IngressRuleValue{
+									HTTP: &networking.HTTPIngressRuleValue{
+										Paths: []networking.HTTPIngressPath{
+											{
+												Path:     "/",
+												PathType: &pathTypePrefix,
+												Backend: networking.IngressBackend{
+													ServiceName: "http-svc-canary",
+													ServicePort: intstr.IntOrString{
+														IntVal: 80,
+													},
+												},
+											},
+										},
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+			map[string]*ingress.Backend{
+				"example-http-svc-80": {
+					Name:     "example-http-svc-80",
+					NoServer: false,
+				},
+				"example-http-svc-canary-80": {
+					Name:     "example-http-svc-canary-80",
+					NoServer: true,
+					TrafficShapingPolicy: ingress.TrafficShapingPolicy{
+						Weight: 20,
+					},
+				},
+			},
+			map[string]*ingress.Server{
+				"_": {
+					Hostname: "_",
+					Locations: []*ingress.Location{
+						{
+							Path:     "/",
+							PathType: &pathTypePrefix,
+							Backend:  "example-http-svc-80",
+						},
+					},
+				},
+			},
+			map[string]*ingress.Backend{
+				"example-http-svc-80": {
+					Name:                "example-http-svc-80",
+					NoServer:            false,
+					AlternativeBackends: []string{"example-http-svc-canary-80"},
+				},
+				"example-http-svc-canary-80": {
+					Name:     "example-http-svc-canary-80",
+					NoServer: true,
+					TrafficShapingPolicy: ingress.TrafficShapingPolicy{
+						Weight: 20,
+					},
+				},
+			},
+			map[string]*ingress.Server{
+				"_": {
+					Hostname: "_",
+					Locations: []*ingress.Location{
+						{
+							Path:     "/",
+							PathType: &pathTypePrefix,
+							Backend:  "example-http-svc-80",
+						},
+					},
+				},
+			},
+		},
 	}
 
 	for title, tc := range testCases {