Copy grpc xDS client from grpc-go

Signed-off-by: Miek Gieben <miek@miek.nl>

plugin/traffic/xds/locality.go

@@ -0,0 +1,50 @@
+/*
+ *
+ * Copyright 2019 gRPC 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 xds
+
+import (
+	"fmt"
+
+	corepb "github.com/envoyproxy/go-control-plane/envoy/api/v2/core"
+)
+
+// Locality is xds.Locality without XXX fields, so it can be used as map
+// keys.
+//
+// xds.Locality cannot be map keys because one of the XXX fields is a slice.
+//
+// This struct should only be used as map keys. Use the proto message directly
+// in all other places.
+type LocalityID struct {
+	Region  string
+	Zone    string
+	SubZone string
+}
+
+func (l LocalityID) String() string {
+	return fmt.Sprintf("%s-%s-%s", l.Region, l.Zone, l.SubZone)
+}
+
+// ToProto convert Locality to the proto representation.
+func (l LocalityID) ToProto() *corepb.Locality {
+	return &corepb.Locality{
+		Region:  l.Region,
+		Zone:    l.Zone,
+		SubZone: l.SubZone,
+	}
+}