clientv3: small client wrapper

mostly to standardize etcd grpc dials

clientv3/client.go

@@ -0,0 +1,98 @@
+// Copyright 2016 CoreOS, Inc.
+//
+// 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 clientv3
+
+import (
+	"github.com/coreos/etcd/Godeps/_workspace/src/google.golang.org/grpc"
+	pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
+)
+
+type Client struct {
+	// KV is the keyvalue API for the client's connection.
+	KV pb.KVClient
+	// Lease is the lease API for the client's connection.
+	Lease pb.LeaseClient
+	// Watch is the watch API for the client's connection.
+	Watch pb.WatchClient
+	// Cluster is the cluster API for the client's connection.
+	Cluster pb.ClusterClient
+
+	conn *grpc.ClientConn
+	cfg  Config
+}
+
+type Config struct {
+	// Endpoints is a list of URLs
+	Endpoints []string
+
+	// TODO TLS options
+}
+
+// New creates a new etcdv3 client from a given configuration.
+func New(cfg Config) (*Client, error) {
+	conn, err := cfg.dialEndpoints()
+	if err != nil {
+		return nil, err
+	}
+	client := newClient(conn)
+	client.cfg = cfg
+	return client, nil
+}
+
+// NewFromURL creates a new etcdv3 client from a URL.
+func NewFromURL(url string) (*Client, error) {
+	return New(Config{Endpoints: []string{url}})
+}
+
+// NewFromConn creates a new etcdv3 client from an established grpc Connection.
+func NewFromConn(conn *grpc.ClientConn) *Client {
+	return newClient(conn)
+}
+
+// Clone creates a copy of client with the old connection and new API clients.
+func (c *Client) Clone() *Client {
+	cl := newClient(c.conn)
+	cl.cfg = c.cfg
+	return cl
+}
+
+// Close shuts down the client's etcd connections.
+func (c *Client) Close() error {
+	return c.conn.Close()
+}
+
+func newClient(conn *grpc.ClientConn) *Client {
+	return &Client{
+		KV:      pb.NewKVClient(conn),
+		Lease:   pb.NewLeaseClient(conn),
+		Watch:   pb.NewWatchClient(conn),
+		Cluster: pb.NewClusterClient(conn),
+		conn:    conn,
+	}
+}
+
+func (cfg *Config) dialEndpoints() (*grpc.ClientConn, error) {
+	var err error
+	for _, ep := range cfg.Endpoints {
+		// TODO: enable grpc.WithTransportCredentials(creds)
+		conn, curErr := grpc.Dial(ep, grpc.WithInsecure())
+		if err != nil {
+			err = curErr
+		} else {
+			return conn, nil
+		}
+	}
+	return nil, err
+}