configuring load balancing per ingress (#2167)

* configure load balancing through a ingress annotation

* update docs

internal/ingress/annotations/annotations.go

@@ -34,6 +34,7 @@ import (
 	"k8s.io/ingress-nginx/internal/ingress/annotations/defaultbackend"
 	"k8s.io/ingress-nginx/internal/ingress/annotations/healthcheck"
 	"k8s.io/ingress-nginx/internal/ingress/annotations/ipwhitelist"
+	"k8s.io/ingress-nginx/internal/ingress/annotations/loadbalancing"
 	"k8s.io/ingress-nginx/internal/ingress/annotations/log"
 	"k8s.io/ingress-nginx/internal/ingress/annotations/parser"
 	"k8s.io/ingress-nginx/internal/ingress/annotations/portinredirect"
@@ -83,6 +84,7 @@ type Ingress struct {
 	SSLPassthrough       bool
 	UsePortInRedirects   bool
 	UpstreamHashBy       string
+	LoadBalancing        string
 	UpstreamVhost        string
 	VtsFilterKey         string
 	Whitelist            ipwhitelist.SourceRange
@@ -121,6 +123,7 @@ func NewAnnotationExtractor(cfg resolver.Resolver) Extractor {
 			"SSLPassthrough":       sslpassthrough.NewParser(cfg),
 			"UsePortInRedirects":   portinredirect.NewParser(cfg),
 			"UpstreamHashBy":       upstreamhashby.NewParser(cfg),
+			"LoadBalancing":        loadbalancing.NewParser(cfg),
 			"UpstreamVhost":        upstreamvhost.NewParser(cfg),
 			"VtsFilterKey":         vtsfilterkey.NewParser(cfg),
 			"Whitelist":            ipwhitelist.NewParser(cfg),

internal/ingress/annotations/loadbalancing/main.go

@@ -0,0 +1,40 @@
+/*
+Copyright 2016 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package loadbalancing
+
+import (
+	extensions "k8s.io/api/extensions/v1beta1"
+
+	"k8s.io/ingress-nginx/internal/ingress/annotations/parser"
+	"k8s.io/ingress-nginx/internal/ingress/resolver"
+)
+
+type loadbalancing struct {
+	r resolver.Resolver
+}
+
+// NewParser creates a new CORS annotation parser
+func NewParser(r resolver.Resolver) parser.IngressAnnotation {
+	return loadbalancing{r}
+}
+
+// Parse parses the annotations contained in the ingress rule
+// used to indicate if the location/s contains a fragment of
+// configuration to be included inside the paths of the rules
+func (a loadbalancing) Parse(ing *extensions.Ingress) (interface{}, error) {
+	return parser.GetStringAnnotation("load-balance", ing)
+}

internal/ingress/annotations/loadbalancing/main_test.go

@@ -0,0 +1,61 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package loadbalancing
+
+import (
+	"testing"
+
+	api "k8s.io/api/core/v1"
+	extensions "k8s.io/api/extensions/v1beta1"
+	meta_v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/ingress-nginx/internal/ingress/annotations/parser"
+	"k8s.io/ingress-nginx/internal/ingress/resolver"
+)
+
+func TestParse(t *testing.T) {
+	annotation := parser.GetAnnotationWithPrefix("load-balance")
+
+	ap := NewParser(&resolver.Mock{})
+	if ap == nil {
+		t.Fatalf("expected a parser.IngressAnnotation but returned nil")
+	}
+
+	testCases := []struct {
+		annotations map[string]string
+		expected    string
+	}{
+		{map[string]string{annotation: "ip_hash"}, "ip_hash"},
+		{map[string]string{}, ""},
+		{nil, ""},
+	}
+
+	ing := &extensions.Ingress{
+		ObjectMeta: meta_v1.ObjectMeta{
+			Name:      "foo",
+			Namespace: api.NamespaceDefault,
+		},
+		Spec: extensions.IngressSpec{},
+	}
+
+	for _, testCase := range testCases {
+		ing.SetAnnotations(testCase.annotations)
+		result, _ := ap.Parse(ing)
+		if result != testCase.expected {
+			t.Errorf("expected %v but returned %v, annotations: %s", testCase.expected, result, testCase.annotations)
+		}
+	}
+}