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client.go
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client.go
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// Copyright 2016 The etcd 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 clientv3
import (
"crypto/tls"
"errors"
"fmt"
"io/ioutil"
"log"
"net"
"net/url"
"strings"
"time"
"github.com/coreos/etcd/etcdserver/api/v3rpc/rpctypes"
"golang.org/x/net/context"
"google.golang.org/grpc"
"google.golang.org/grpc/credentials"
"google.golang.org/grpc/metadata"
)
var (
ErrNoAvailableEndpoints = errors.New("etcdclient: no available endpoints")
)
// Client provides and manages an etcd v3 client session.
type Client struct {
Cluster
KV
Lease
Watcher
Auth
Maintenance
conn *grpc.ClientConn
cfg Config
creds *credentials.TransportCredentials
ctx context.Context
cancel context.CancelFunc
// Username is a username for authentication
Username string
// Password is a password for authentication
Password string
}
// New creates a new etcdv3 client from a given configuration.
func New(cfg Config) (*Client, error) {
if len(cfg.Endpoints) == 0 {
return nil, ErrNoAvailableEndpoints
}
return newClient(&cfg)
}
// NewFromURL creates a new etcdv3 client from a URL.
func NewFromURL(url string) (*Client, error) {
return New(Config{Endpoints: []string{url}})
}
// NewFromConfigFile creates a new etcdv3 client from a configuration file.
func NewFromConfigFile(path string) (*Client, error) {
cfg, err := configFromFile(path)
if err != nil {
return nil, err
}
return New(*cfg)
}
// Close shuts down the client's etcd connections.
func (c *Client) Close() error {
c.cancel()
return toErr(c.ctx, c.conn.Close())
}
// Ctx is a context for "out of band" messages (e.g., for sending
// "clean up" message when another context is canceled). It is
// canceled on client Close().
func (c *Client) Ctx() context.Context { return c.ctx }
// Endpoints lists the registered endpoints for the client.
func (c *Client) Endpoints() []string { return c.cfg.Endpoints }
type authTokenCredential struct {
token string
}
func (cred authTokenCredential) RequireTransportSecurity() bool {
return false
}
func (cred authTokenCredential) GetRequestMetadata(ctx context.Context, s ...string) (map[string]string, error) {
return map[string]string{
"token": cred.token,
}, nil
}
func (c *Client) dialTarget(endpoint string) (proto string, host string, creds *credentials.TransportCredentials) {
proto = "tcp"
host = endpoint
creds = c.creds
url, uerr := url.Parse(endpoint)
if uerr != nil || !strings.Contains(endpoint, "://") {
return
}
// strip scheme:// prefix since grpc dials by host
host = url.Host
switch url.Scheme {
case "unix":
proto = "unix"
case "http":
creds = nil
case "https":
if creds != nil {
break
}
tlsconfig := &tls.Config{}
emptyCreds := credentials.NewTLS(tlsconfig)
creds = &emptyCreds
default:
return "", "", nil
}
return
}
// dialSetupOpts gives the dial opts prioer to any authentication
func (c *Client) dialSetupOpts(endpoint string, dopts ...grpc.DialOption) []grpc.DialOption {
opts := []grpc.DialOption{
grpc.WithBlock(),
grpc.WithTimeout(c.cfg.DialTimeout),
}
opts = append(opts, dopts...)
// grpc issues TLS cert checks using the string passed into dial so
// that string must be the host. To recover the full scheme://host URL,
// have a map from hosts to the original endpoint.
host2ep := make(map[string]string)
for i := range c.cfg.Endpoints {
_, host, _ := c.dialTarget(c.cfg.Endpoints[i])
host2ep[host] = c.cfg.Endpoints[i]
}
f := func(host string, t time.Duration) (net.Conn, error) {
proto, host, _ := c.dialTarget(host2ep[host])
if proto == "" {
return nil, fmt.Errorf("unknown scheme for %q", host)
}
select {
case <-c.ctx.Done():
return nil, c.ctx.Err()
default:
}
return net.DialTimeout(proto, host, t)
}
opts = append(opts, grpc.WithDialer(f))
_, _, creds := c.dialTarget(endpoint)
if creds != nil {
opts = append(opts, grpc.WithTransportCredentials(*creds))
} else {
opts = append(opts, grpc.WithInsecure())
}
return opts
}
// Dial connects to a single endpoint using the client's config.
func (c *Client) Dial(endpoint string) (*grpc.ClientConn, error) {
return c.dial(endpoint)
}
func (c *Client) dial(endpoint string, dopts ...grpc.DialOption) (*grpc.ClientConn, error) {
opts := c.dialSetupOpts(endpoint, dopts...)
host := getHost(endpoint)
if c.Username != "" && c.Password != "" {
// use dial options without dopts to avoid reusing the client balancer
auth, err := newAuthenticator(host, c.dialSetupOpts(endpoint))
if err != nil {
return nil, err
}
defer auth.close()
resp, err := auth.authenticate(c.ctx, c.Username, c.Password)
if err != nil {
return nil, err
}
opts = append(opts, grpc.WithPerRPCCredentials(authTokenCredential{token: resp.Token}))
}
conn, err := grpc.Dial(host, opts...)
if err != nil {
return nil, err
}
return conn, nil
}
// WithRequireLeader requires client requests to only succeed
// when the cluster has a leader.
func WithRequireLeader(ctx context.Context) context.Context {
md := metadata.Pairs(rpctypes.MetadataRequireLeaderKey, rpctypes.MetadataHasLeader)
return metadata.NewContext(ctx, md)
}
func newClient(cfg *Config) (*Client, error) {
if cfg == nil {
cfg = &Config{}
}
var creds *credentials.TransportCredentials
if cfg.TLS != nil {
c := credentials.NewTLS(cfg.TLS)
creds = &c
}
// use a temporary skeleton client to bootstrap first connection
ctx, cancel := context.WithCancel(context.TODO())
client := &Client{
conn: nil,
cfg: *cfg,
creds: creds,
ctx: ctx,
cancel: cancel,
}
if cfg.Username != "" && cfg.Password != "" {
client.Username = cfg.Username
client.Password = cfg.Password
}
b := newSimpleBalancer(cfg.Endpoints)
conn, err := client.dial(cfg.Endpoints[0], grpc.WithBalancer(b))
if err != nil {
return nil, err
}
client.conn = conn
client.Cluster = NewCluster(client)
client.KV = NewKV(client)
client.Lease = NewLease(client)
client.Watcher = NewWatcher(client)
client.Auth = NewAuth(client)
client.Maintenance = NewMaintenance(client)
if cfg.Logger != nil {
logger.Set(cfg.Logger)
} else {
// disable client side grpc by default
logger.Set(log.New(ioutil.Discard, "", 0))
}
return client, nil
}
// ActiveConnection returns the current in-use connection
func (c *Client) ActiveConnection() *grpc.ClientConn { return c.conn }
// isHaltErr returns true if the given error and context indicate no forward
// progress can be made, even after reconnecting.
func isHaltErr(ctx context.Context, err error) bool {
if ctx != nil && ctx.Err() != nil {
return true
}
if err == nil {
return false
}
return strings.HasPrefix(grpc.ErrorDesc(err), "etcdserver: ") ||
strings.Contains(err.Error(), grpc.ErrClientConnClosing.Error())
}
func toErr(ctx context.Context, err error) error {
if err == nil {
return nil
}
err = rpctypes.Error(err)
if ctx.Err() != nil && strings.Contains(err.Error(), "context") {
err = ctx.Err()
} else if strings.Contains(err.Error(), grpc.ErrClientConnClosing.Error()) {
err = grpc.ErrClientConnClosing
}
return err
}