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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"
"net"
"net/url"
"strconv"
"strings"
"sync"
"time"
"github.com/coreos/etcd/etcdserver/api/v3rpc/rpctypes"
"golang.org/x/net/context"
"google.golang.org/grpc"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/credentials"
"google.golang.org/grpc/metadata"
)
var (
ErrNoAvailableEndpoints = errors.New("etcdclient: no available endpoints")
ErrOldCluster = errors.New("etcdclient: old cluster version")
)
// Client provides and manages an etcd v3 client session.
type Client struct {
Cluster
KV
Lease
Watcher
Auth
Maintenance
conn *grpc.ClientConn
dialerrc chan error
cfg Config
creds *credentials.TransportCredentials
balancer *simpleBalancer
retryWrapper retryRpcFunc
retryAuthWrapper retryRpcFunc
ctx context.Context
cancel context.CancelFunc
// Username is a username for authentication
Username string
// Password is a password for authentication
Password string
// tokenCred is an instance of WithPerRPCCredentials()'s argument
tokenCred *authTokenCredential
}
// 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)
}
// NewCtxClient creates a client with a context but no underlying grpc
// connection. This is useful for embedded cases that override the
// service interface implementations and do not need connection management.
func NewCtxClient(ctx context.Context) *Client {
cctx, cancel := context.WithCancel(ctx)
return &Client{ctx: cctx, cancel: cancel}
}
// NewFromURL creates a new etcdv3 client from a URL.
func NewFromURL(url string) (*Client, error) {
return New(Config{Endpoints: []string{url}})
}
// Close shuts down the client's etcd connections.
func (c *Client) Close() error {
c.cancel()
c.Watcher.Close()
c.Lease.Close()
if c.conn != nil {
return toErr(c.ctx, c.conn.Close())
}
return c.ctx.Err()
}
// 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() (eps []string) {
// copy the slice; protect original endpoints from being changed
eps = make([]string, len(c.cfg.Endpoints))
copy(eps, c.cfg.Endpoints)
return
}
// SetEndpoints updates client's endpoints.
func (c *Client) SetEndpoints(eps ...string) {
c.cfg.Endpoints = eps
c.balancer.updateAddrs(eps)
}
// Sync synchronizes client's endpoints with the known endpoints from the etcd membership.
func (c *Client) Sync(ctx context.Context) error {
mresp, err := c.MemberList(ctx)
if err != nil {
return err
}
var eps []string
for _, m := range mresp.Members {
eps = append(eps, m.ClientURLs...)
}
c.SetEndpoints(eps...)
return nil
}
func (c *Client) autoSync() {
if c.cfg.AutoSyncInterval == time.Duration(0) {
return
}
for {
select {
case <-c.ctx.Done():
return
case <-time.After(c.cfg.AutoSyncInterval):
ctx, _ := context.WithTimeout(c.ctx, 5*time.Second)
if err := c.Sync(ctx); err != nil && err != c.ctx.Err() {
logger.Println("Auto sync endpoints failed:", err)
}
}
}
}
type authTokenCredential struct {
token string
tokenMu *sync.RWMutex
}
func (cred authTokenCredential) RequireTransportSecurity() bool {
return false
}
func (cred authTokenCredential) GetRequestMetadata(ctx context.Context, s ...string) (map[string]string, error) {
cred.tokenMu.RLock()
defer cred.tokenMu.RUnlock()
return map[string]string{
"token": cred.token,
}, nil
}
func parseEndpoint(endpoint string) (proto string, host string, scheme string) {
proto = "tcp"
host = endpoint
url, uerr := url.Parse(endpoint)
if uerr != nil || !strings.Contains(endpoint, "://") {
return
}
scheme = url.Scheme
// strip scheme:// prefix since grpc dials by host
host = url.Host
switch url.Scheme {
case "http", "https":
case "unix", "unixs":
proto = "unix"
host = url.Host + url.Path
default:
proto, host = "", ""
}
return
}
func (c *Client) processCreds(scheme string) (creds *credentials.TransportCredentials) {
creds = c.creds
switch scheme {
case "unix":
case "http":
creds = nil
case "https", "unixs":
if creds != nil {
break
}
tlsconfig := &tls.Config{}
emptyCreds := credentials.NewTLS(tlsconfig)
creds = &emptyCreds
default:
creds = nil
}
return
}
// dialSetupOpts gives the dial opts prior to any authentication
func (c *Client) dialSetupOpts(endpoint string, dopts ...grpc.DialOption) (opts []grpc.DialOption) {
if c.cfg.DialTimeout > 0 {
opts = []grpc.DialOption{grpc.WithTimeout(c.cfg.DialTimeout)}
}
opts = append(opts, dopts...)
f := func(host string, t time.Duration) (net.Conn, error) {
proto, host, _ := parseEndpoint(c.balancer.getEndpoint(host))
if host == "" && endpoint != "" {
// dialing an endpoint not in the balancer; use
// endpoint passed into dial
proto, host, _ = parseEndpoint(endpoint)
}
if proto == "" {
return nil, fmt.Errorf("unknown scheme for %q", host)
}
select {
case <-c.ctx.Done():
return nil, c.ctx.Err()
default:
}
dialer := &net.Dialer{Timeout: t}
conn, err := dialer.DialContext(c.ctx, proto, host)
if err != nil {
select {
case c.dialerrc <- err:
default:
}
}
return conn, err
}
opts = append(opts, grpc.WithDialer(f))
creds := c.creds
if _, _, scheme := parseEndpoint(endpoint); len(scheme) != 0 {
creds = c.processCreds(scheme)
}
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) getToken(ctx context.Context) error {
var err error // return last error in a case of fail
var auth *authenticator
for i := 0; i < len(c.cfg.Endpoints); i++ {
endpoint := c.cfg.Endpoints[i]
host := getHost(endpoint)
// use dial options without dopts to avoid reusing the client balancer
auth, err = newAuthenticator(host, c.dialSetupOpts(endpoint))
if err != nil {
continue
}
defer auth.close()
var resp *AuthenticateResponse
resp, err = auth.authenticate(ctx, c.Username, c.Password)
if err != nil {
continue
}
c.tokenCred.tokenMu.Lock()
c.tokenCred.token = resp.Token
c.tokenCred.tokenMu.Unlock()
return nil
}
return err
}
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 != "" {
c.tokenCred = &authTokenCredential{
tokenMu: &sync.RWMutex{},
}
ctx := c.ctx
if c.cfg.DialTimeout > 0 {
cctx, cancel := context.WithTimeout(ctx, c.cfg.DialTimeout)
defer cancel()
ctx = cctx
}
err := c.getToken(ctx)
if err != nil {
if toErr(ctx, err) != rpctypes.ErrAuthNotEnabled {
if err == ctx.Err() && ctx.Err() != c.ctx.Err() {
err = grpc.ErrClientConnTimeout
}
return nil, err
}
} else {
opts = append(opts, grpc.WithPerRPCCredentials(c.tokenCred))
}
}
opts = append(opts, c.cfg.DialOptions...)
conn, err := grpc.DialContext(c.ctx, 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
baseCtx := context.TODO()
if cfg.Context != nil {
baseCtx = cfg.Context
}
ctx, cancel := context.WithCancel(baseCtx)
client := &Client{
conn: nil,
dialerrc: make(chan error, 1),
cfg: *cfg,
creds: creds,
ctx: ctx,
cancel: cancel,
}
if cfg.Username != "" && cfg.Password != "" {
client.Username = cfg.Username
client.Password = cfg.Password
}
client.balancer = newSimpleBalancer(cfg.Endpoints)
// use Endpoints[0] so that for https:// without any tls config given, then
// grpc will assume the ServerName is in the endpoint.
conn, err := client.dial(cfg.Endpoints[0], grpc.WithBalancer(client.balancer))
if err != nil {
client.cancel()
client.balancer.Close()
return nil, err
}
client.conn = conn
client.retryWrapper = client.newRetryWrapper()
client.retryAuthWrapper = client.newAuthRetryWrapper()
// wait for a connection
if cfg.DialTimeout > 0 {
hasConn := false
waitc := time.After(cfg.DialTimeout)
select {
case <-client.balancer.readyc:
hasConn = true
case <-ctx.Done():
case <-waitc:
}
if !hasConn {
err := grpc.ErrClientConnTimeout
select {
case err = <-client.dialerrc:
default:
}
client.cancel()
client.balancer.Close()
conn.Close()
return nil, err
}
}
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.RejectOldCluster {
if err := client.checkVersion(); err != nil {
client.Close()
return nil, err
}
}
go client.autoSync()
return client, nil
}
func (c *Client) checkVersion() (err error) {
var wg sync.WaitGroup
errc := make(chan error, len(c.cfg.Endpoints))
ctx, cancel := context.WithCancel(c.ctx)
if c.cfg.DialTimeout > 0 {
ctx, _ = context.WithTimeout(ctx, c.cfg.DialTimeout)
}
wg.Add(len(c.cfg.Endpoints))
for _, ep := range c.cfg.Endpoints {
// if cluster is current, any endpoint gives a recent version
go func(e string) {
defer wg.Done()
resp, rerr := c.Status(ctx, e)
if rerr != nil {
errc <- rerr
return
}
vs := strings.Split(resp.Version, ".")
maj, min := 0, 0
if len(vs) >= 2 {
maj, rerr = strconv.Atoi(vs[0])
min, rerr = strconv.Atoi(vs[1])
}
if maj < 3 || (maj == 3 && min < 2) {
rerr = ErrOldCluster
}
errc <- rerr
}(ep)
}
// wait for success
for i := 0; i < len(c.cfg.Endpoints); i++ {
if err = <-errc; err == nil {
break
}
}
cancel()
wg.Wait()
return err
}
// 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
}
code := grpc.Code(err)
// Unavailable codes mean the system will be right back.
// (e.g., can't connect, lost leader)
// Treat Internal codes as if something failed, leaving the
// system in an inconsistent state, but retrying could make progress.
// (e.g., failed in middle of send, corrupted frame)
// TODO: are permanent Internal errors possible from grpc?
return code != codes.Unavailable && code != codes.Internal
}
func toErr(ctx context.Context, err error) error {
if err == nil {
return nil
}
err = rpctypes.Error(err)
if _, ok := err.(rpctypes.EtcdError); ok {
return err
}
code := grpc.Code(err)
switch code {
case codes.DeadlineExceeded:
fallthrough
case codes.Canceled:
if ctx.Err() != nil {
err = ctx.Err()
}
case codes.Unavailable:
err = ErrNoAvailableEndpoints
case codes.FailedPrecondition:
err = grpc.ErrClientConnClosing
}
return err
}
func canceledByCaller(stopCtx context.Context, err error) bool {
if stopCtx.Err() == nil || err == nil {
return false
}
return err == context.Canceled || err == context.DeadlineExceeded
}