add flags to enable etcd3

pkg/storage/storagebackend/config.go

@@ -0,0 +1,68 @@
+/*
+Copyright 2016 The Kubernetes Authors All rights reserved.
+
+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 storagebackend
+
+import (
+	"fmt"
+
+	"k8s.io/kubernetes/pkg/runtime"
+	"k8s.io/kubernetes/pkg/storage"
+)
+
+const (
+	StorageTypeUnset = ""
+	StorageTypeETCD2 = "etcd2"
+	StorageTypeETCD3 = "etcd3"
+)
+
+// Config is configuration for creating a storage backend.
+type Config struct {
+	// Type defines the type of storage backend, e.g. "etcd2", etcd3". Default ("") is "etcd2".
+	Type string
+	// Codec is used to serialize/deserialize objects.
+	Codec runtime.Codec
+	// Prefix is the prefix to all keys passed to storage.Interface methods.
+	Prefix string
+	// ServerList is the list of storage servers to connect with.
+	ServerList []string
+	// TLS credentials
+	KeyFile  string
+	CertFile string
+	CAFile   string
+	// Quorum indicates that whether read operations should be quorum-level consistent.
+	Quorum bool
+	// DeserializationCacheSize is the size of cache of deserialized objects.
+	// Currently this is only supported in etcd2.
+	// We will drop the cache once using protobuf.
+	DeserializationCacheSize int
+}
+
+// Create creates a storage backend based on given config.
+func Create(c Config) (storage.Interface, error) {
+	switch c.Type {
+	case StorageTypeUnset, StorageTypeETCD2:
+		return newETCD2Storage(c)
+	case StorageTypeETCD3:
+		// TODO: We have the following features to implement:
+		// - Support secure connection by using key, cert, and CA files.
+		// - Honor "https" scheme to support secure connection in gRPC.
+		// - Support non-quorum read.
+		return newETCD3Storage(c)
+	default:
+		return nil, fmt.Errorf("unknown storage type: %s", c.Type)
+	}
+}