Consistent hashing to a subset of nodes. It works like consistent hash,

but instead of mapping to a single node, we map to a subset of nodes.

internal/ingress/annotations/annotations.go

@@ -92,7 +92,7 @@ type Ingress struct {
 	SessionAffinity      sessionaffinity.Config
 	SSLPassthrough       bool
 	UsePortInRedirects   bool
-	UpstreamHashBy       string
+	UpstreamHashBy       upstreamhashby.Config
 	LoadBalancing        string
 	UpstreamVhost        string
 	Whitelist            ipwhitelist.SourceRange

internal/ingress/annotations/annotations_test.go

@@ -186,7 +186,7 @@ func TestUpstreamHashBy(t *testing.T) {
 
 	for _, foo := range fooAnns {
 		ing.SetAnnotations(foo.annotations)
-		r := ec.Extract(ing).UpstreamHashBy
+		r := ec.Extract(ing).UpstreamHashBy.UpstreamHashBy
 		if r != foo.er {
 			t.Errorf("Returned %v but expected %v", r, foo.er)
 		}

internal/ingress/annotations/upstreamhashby/main.go

@@ -27,14 +27,27 @@ type upstreamhashby struct {
 	r resolver.Resolver
 }
 
-// NewParser creates a new CORS annotation parser
+// Config contains the Consistent hash configuration to be used in the Ingress
+type Config struct {
+	UpstreamHashBy           string `json:"upstream-hash-by,omitempty"`
+	UpstreamHashBySubset     bool   `json:"upstream-hash-by-subset,omitempty"`
+	UpstreamHashBySubsetSize int    `json:"upstream-hash-by-subset-size,omitempty"`
+}
+
+// NewParser creates a new UpstreamHashBy annotation parser
 func NewParser(r resolver.Resolver) parser.IngressAnnotation {
 	return upstreamhashby{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 upstreamhashby) Parse(ing *extensions.Ingress) (interface{}, error) {
-	return parser.GetStringAnnotation("upstream-hash-by", ing)
+	upstreamHashBy, _ := parser.GetStringAnnotation("upstream-hash-by", ing)
+	upstreamHashBySubset, _ := parser.GetBoolAnnotation("upstream-hash-by-subset", ing)
+	upstreamHashbySubsetSize, _ := parser.GetIntAnnotation("upstream-hash-by-subset-size", ing)
+
+	if upstreamHashbySubsetSize == 0 {
+		upstreamHashbySubsetSize = 3
+	}
+
+	return &Config{upstreamHashBy, upstreamHashBySubset, upstreamHashbySubsetSize}, nil
 }

internal/ingress/annotations/upstreamhashby/main_test.go

@@ -55,7 +55,12 @@ func TestParse(t *testing.T) {
 	for _, testCase := range testCases {
 		ing.SetAnnotations(testCase.annotations)
 		result, _ := ap.Parse(ing)
-		if result != testCase.expected {
+		uc, ok := result.(*Config)
+		if !ok {
+			t.Fatalf("expected a Config type")
+		}
+
+		if uc.UpstreamHashBy != testCase.expected {
 			t.Errorf("expected %v but returned %v, annotations: %s", testCase.expected, result, testCase.annotations)
 		}
 	}