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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 (
"context"
"errors"
"fmt"
"net"
"os"
"strconv"
"strings"
"sync"
"time"
"github.com/google/uuid"
"go.etcd.io/etcd/clientv3/balancer"
"go.etcd.io/etcd/clientv3/balancer/picker"
"go.etcd.io/etcd/clientv3/balancer/resolver/endpoint"
"go.etcd.io/etcd/clientv3/credentials"
"go.etcd.io/etcd/etcdserver/api/v3rpc/rpctypes"
"go.etcd.io/etcd/pkg/logutil"
"go.uber.org/zap"
"google.golang.org/grpc"
"google.golang.org/grpc/codes"
grpccredentials "google.golang.org/grpc/credentials"
"google.golang.org/grpc/keepalive"
"google.golang.org/grpc/metadata"
"google.golang.org/grpc/status"
)
var (
ErrNoAvailableEndpoints = errors.New("etcdclient: no available endpoints")
ErrOldCluster = errors.New("etcdclient: old cluster version")
roundRobinBalancerName = fmt.Sprintf("etcd-%s", picker.RoundrobinBalanced.String())
)
func init() {
lg := zap.NewNop()
if os.Getenv("ETCD_CLIENT_DEBUG") != "" {
lcfg := logutil.DefaultZapLoggerConfig
lcfg.Level = zap.NewAtomicLevelAt(zap.DebugLevel)
var err error
lg, err = lcfg.Build() // info level logging
if err != nil {
panic(err)
}
}
// TODO: support custom balancer
balancer.RegisterBuilder(balancer.Config{
Policy: picker.RoundrobinBalanced,
Name: roundRobinBalancerName,
Logger: lg,
})
}
// Client provides and manages an etcd v3 client session.
type Client struct {
Cluster
KV
Lease
Watcher
Auth
Maintenance
conn *grpc.ClientConn
cfg Config
creds grpccredentials.TransportCredentials
resolverGroup *endpoint.ResolverGroup
mu *sync.RWMutex
ctx context.Context
cancel context.CancelFunc
// Username is a user name for authentication.
Username string
// Password is a password for authentication.
Password string
authTokenBundle credentials.Bundle
callOpts []grpc.CallOption
lg *zap.Logger
}
// 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}})
}
// NewFromURLs creates a new etcdv3 client from URLs.
func NewFromURLs(urls []string) (*Client, error) {
return New(Config{Endpoints: urls})
}
// Close shuts down the client's etcd connections.
func (c *Client) Close() error {
c.cancel()
if c.Watcher != nil {
c.Watcher.Close()
}
if c.Lease != nil {
c.Lease.Close()
}
if c.resolverGroup != nil {
c.resolverGroup.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() []string {
// copy the slice; protect original endpoints from being changed
c.mu.RLock()
defer c.mu.RUnlock()
eps := make([]string, len(c.cfg.Endpoints))
copy(eps, c.cfg.Endpoints)
return eps
}
// SetEndpoints updates client's endpoints.
func (c *Client) SetEndpoints(eps ...string) {
c.mu.Lock()
defer c.mu.Unlock()
c.cfg.Endpoints = eps
c.resolverGroup.SetEndpoints(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, cancel := context.WithTimeout(c.ctx, 5*time.Second)
err := c.Sync(ctx)
cancel()
if err != nil && err != c.ctx.Err() {
lg.Lvl(4).Infof("Auto sync endpoints failed: %v", err)
}
}
}
}
func (c *Client) processCreds(scheme string) (creds grpccredentials.TransportCredentials) {
creds = c.creds
switch scheme {
case "unix":
case "http":
creds = nil
case "https", "unixs":
if creds != nil {
break
}
creds = credentials.NewBundle(credentials.Config{}).TransportCredentials()
default:
creds = nil
}
return creds
}
// dialSetupOpts gives the dial opts prior to any authentication.
func (c *Client) dialSetupOpts(creds grpccredentials.TransportCredentials, dopts ...grpc.DialOption) (opts []grpc.DialOption, err error) {
if c.cfg.DialKeepAliveTime > 0 {
params := keepalive.ClientParameters{
Time: c.cfg.DialKeepAliveTime,
Timeout: c.cfg.DialKeepAliveTimeout,
PermitWithoutStream: c.cfg.PermitWithoutStream,
}
opts = append(opts, grpc.WithKeepaliveParams(params))
}
opts = append(opts, dopts...)
// Provide a net dialer that supports cancelation and timeout.
f := func(dialEp string, t time.Duration) (net.Conn, error) {
proto, host, _ := endpoint.ParseEndpoint(dialEp)
select {
case <-c.ctx.Done():
return nil, c.ctx.Err()
default:
}
dialer := &net.Dialer{Timeout: t}
return dialer.DialContext(c.ctx, proto, host)
}
opts = append(opts, grpc.WithDialer(f))
if creds != nil {
opts = append(opts, grpc.WithTransportCredentials(creds))
} else {
opts = append(opts, grpc.WithInsecure())
}
// Interceptor retry and backoff.
// TODO: Replace all of clientv3/retry.go with interceptor based retry, or with
// https://github.com/grpc/proposal/blob/master/A6-client-retries.md#retry-policy
// once it is available.
rrBackoff := withBackoff(c.roundRobinQuorumBackoff(defaultBackoffWaitBetween, defaultBackoffJitterFraction))
opts = append(opts,
// Disable stream retry by default since go-grpc-middleware/retry does not support client streams.
// Streams that are safe to retry are enabled individually.
grpc.WithStreamInterceptor(c.streamClientInterceptor(c.lg, withMax(0), rrBackoff)),
grpc.WithUnaryInterceptor(c.unaryClientInterceptor(c.lg, withMax(defaultUnaryMaxRetries), rrBackoff)),
)
return opts, nil
}
// Dial connects to a single endpoint using the client's config.
func (c *Client) Dial(ep string) (*grpc.ClientConn, error) {
creds := c.directDialCreds(ep)
// Use the grpc passthrough resolver to directly dial a single endpoint.
// This resolver passes through the 'unix' and 'unixs' endpoints schemes used
// by etcd without modification, allowing us to directly dial endpoints and
// using the same dial functions that we use for load balancer dialing.
return c.dial(fmt.Sprintf("passthrough:///%s", ep), creds)
}
func (c *Client) getToken(ctx context.Context) error {
var err error // return last error in a case of fail
var auth *authenticator
eps := c.Endpoints()
for _, ep := range eps {
// use dial options without dopts to avoid reusing the client balancer
var dOpts []grpc.DialOption
_, host, _ := endpoint.ParseEndpoint(ep)
target := c.resolverGroup.Target(host)
creds := c.dialWithBalancerCreds(ep)
dOpts, err = c.dialSetupOpts(creds, c.cfg.DialOptions...)
if err != nil {
err = fmt.Errorf("failed to configure auth dialer: %v", err)
continue
}
dOpts = append(dOpts, grpc.WithBalancerName(roundRobinBalancerName))
auth, err = newAuthenticator(ctx, target, dOpts, c)
if err != nil {
continue
}
defer auth.close()
var resp *AuthenticateResponse
resp, err = auth.authenticate(ctx, c.Username, c.Password)
if err != nil {
// return err without retrying other endpoints
if err == rpctypes.ErrAuthNotEnabled {
return err
}
continue
}
c.authTokenBundle.UpdateAuthToken(resp.Token)
return nil
}
return err
}
// dialWithBalancer dials the client's current load balanced resolver group. The scheme of the host
// of the provided endpoint determines the scheme used for all endpoints of the client connection.
func (c *Client) dialWithBalancer(ep string, dopts ...grpc.DialOption) (*grpc.ClientConn, error) {
_, host, _ := endpoint.ParseEndpoint(ep)
target := c.resolverGroup.Target(host)
creds := c.dialWithBalancerCreds(ep)
return c.dial(target, creds, dopts...)
}
// dial configures and dials any grpc balancer target.
func (c *Client) dial(target string, creds grpccredentials.TransportCredentials, dopts ...grpc.DialOption) (*grpc.ClientConn, error) {
opts, err := c.dialSetupOpts(creds, dopts...)
if err != nil {
return nil, fmt.Errorf("failed to configure dialer: %v", err)
}
if c.Username != "" && c.Password != "" {
c.authTokenBundle = credentials.NewBundle(credentials.Config{})
ctx, cancel := c.ctx, func() {}
if c.cfg.DialTimeout > 0 {
ctx, cancel = context.WithTimeout(ctx, c.cfg.DialTimeout)
}
err = c.getToken(ctx)
if err != nil {
if toErr(ctx, err) != rpctypes.ErrAuthNotEnabled {
if err == ctx.Err() && ctx.Err() != c.ctx.Err() {
err = context.DeadlineExceeded
}
cancel()
return nil, err
}
} else {
opts = append(opts, grpc.WithPerRPCCredentials(c.authTokenBundle.PerRPCCredentials()))
}
cancel()
}
opts = append(opts, c.cfg.DialOptions...)
dctx := c.ctx
if c.cfg.DialTimeout > 0 {
var cancel context.CancelFunc
dctx, cancel = context.WithTimeout(c.ctx, c.cfg.DialTimeout)
defer cancel() // TODO: Is this right for cases where grpc.WithBlock() is not set on the dial options?
}
conn, err := grpc.DialContext(dctx, target, opts...)
if err != nil {
return nil, err
}
return conn, nil
}
func (c *Client) directDialCreds(ep string) grpccredentials.TransportCredentials {
_, hostPort, scheme := endpoint.ParseEndpoint(ep)
creds := c.creds
if len(scheme) != 0 {
creds = c.processCreds(scheme)
if creds != nil {
clone := creds.Clone()
// Set the server name must to the endpoint hostname without port since grpc
// otherwise attempts to check if x509 cert is valid for the full endpoint
// including the scheme and port, which fails.
host, _ := endpoint.ParseHostPort(hostPort)
clone.OverrideServerName(host)
creds = clone
}
}
return creds
}
func (c *Client) dialWithBalancerCreds(ep string) grpccredentials.TransportCredentials {
_, _, scheme := endpoint.ParseEndpoint(ep)
creds := c.creds
if len(scheme) != 0 {
creds = c.processCreds(scheme)
}
return creds
}
// 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.NewOutgoingContext(ctx, md)
}
func newClient(cfg *Config) (*Client, error) {
if cfg == nil {
cfg = &Config{}
}
var creds grpccredentials.TransportCredentials
if cfg.TLS != nil {
creds = credentials.NewBundle(credentials.Config{TLSConfig: cfg.TLS}).TransportCredentials()
}
// 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,
cfg: *cfg,
creds: creds,
ctx: ctx,
cancel: cancel,
mu: new(sync.RWMutex),
callOpts: defaultCallOpts,
}
lcfg := logutil.DefaultZapLoggerConfig
if cfg.LogConfig != nil {
lcfg = *cfg.LogConfig
}
var err error
client.lg, err = lcfg.Build()
if err != nil {
return nil, err
}
if cfg.Username != "" && cfg.Password != "" {
client.Username = cfg.Username
client.Password = cfg.Password
}
if cfg.MaxCallSendMsgSize > 0 || cfg.MaxCallRecvMsgSize > 0 {
if cfg.MaxCallRecvMsgSize > 0 && cfg.MaxCallSendMsgSize > cfg.MaxCallRecvMsgSize {
return nil, fmt.Errorf("gRPC message recv limit (%d bytes) must be greater than send limit (%d bytes)", cfg.MaxCallRecvMsgSize, cfg.MaxCallSendMsgSize)
}
callOpts := []grpc.CallOption{
defaultFailFast,
defaultMaxCallSendMsgSize,
defaultMaxCallRecvMsgSize,
}
if cfg.MaxCallSendMsgSize > 0 {
callOpts[1] = grpc.MaxCallSendMsgSize(cfg.MaxCallSendMsgSize)
}
if cfg.MaxCallRecvMsgSize > 0 {
callOpts[2] = grpc.MaxCallRecvMsgSize(cfg.MaxCallRecvMsgSize)
}
client.callOpts = callOpts
}
// Prepare a 'endpoint://<unique-client-id>/' resolver for the client and create a endpoint target to pass
// to dial so the client knows to use this resolver.
client.resolverGroup, err = endpoint.NewResolverGroup(fmt.Sprintf("client-%s", uuid.New().String()))
if err != nil {
client.cancel()
return nil, err
}
client.resolverGroup.SetEndpoints(cfg.Endpoints)
if len(cfg.Endpoints) < 1 {
return nil, fmt.Errorf("at least one Endpoint must is required in client config")
}
dialEndpoint := cfg.Endpoints[0]
// Use a provided endpoint target so that for https:// without any tls config given, then
// grpc will assume the certificate server name is the endpoint host.
conn, err := client.dialWithBalancer(dialEndpoint, grpc.WithBalancerName(roundRobinBalancerName))
if err != nil {
client.cancel()
client.resolverGroup.Close()
return nil, err
}
// TODO: With the old grpc balancer interface, we waited until the dial timeout
// for the balancer to be ready. Is there an equivalent wait we should do with the new grpc balancer interface?
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.RejectOldCluster {
if err := client.checkVersion(); err != nil {
client.Close()
return nil, err
}
}
go client.autoSync()
return client, nil
}
// roundRobinQuorumBackoff retries against quorum between each backoff.
// This is intended for use with a round robin load balancer.
func (c *Client) roundRobinQuorumBackoff(waitBetween time.Duration, jitterFraction float64) backoffFunc {
return func(attempt uint) time.Duration {
// after each round robin across quorum, backoff for our wait between duration
n := uint(len(c.Endpoints()))
quorum := (n/2 + 1)
if attempt%quorum == 0 {
c.lg.Debug("backoff", zap.Uint("attempt", attempt), zap.Uint("quorum", quorum), zap.Duration("waitBetween", waitBetween), zap.Float64("jitterFraction", jitterFraction))
return jitterUp(waitBetween, jitterFraction)
}
c.lg.Debug("backoff skipped", zap.Uint("attempt", attempt), zap.Uint("quorum", quorum))
return 0
}
}
func (c *Client) checkVersion() (err error) {
var wg sync.WaitGroup
eps := c.Endpoints()
errc := make(chan error, len(eps))
ctx, cancel := context.WithCancel(c.ctx)
if c.cfg.DialTimeout > 0 {
cancel()
ctx, cancel = context.WithTimeout(c.ctx, c.cfg.DialTimeout)
}
wg.Add(len(eps))
for _, ep := range eps {
// 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 {
var serr error
if maj, serr = strconv.Atoi(vs[0]); serr != nil {
errc <- serr
return
}
if min, serr = strconv.Atoi(vs[1]); serr != nil {
errc <- serr
return
}
}
if maj < 3 || (maj == 3 && min < 2) {
rerr = ErrOldCluster
}
errc <- rerr
}(ep)
}
// wait for success
for range eps {
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
}
ev, _ := status.FromError(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 ev.Code() != codes.Unavailable && ev.Code() != codes.Internal
}
// isUnavailableErr returns true if the given error is an unavailable error
func isUnavailableErr(ctx context.Context, err error) bool {
if ctx != nil && ctx.Err() != nil {
return false
}
if err == nil {
return false
}
ev, ok := status.FromError(err)
if ok {
// Unavailable codes mean the system will be right back.
// (e.g., can't connect, lost leader)
return ev.Code() == codes.Unavailable
}
return false
}
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
}
if ev, ok := status.FromError(err); ok {
code := ev.Code()
switch code {
case codes.DeadlineExceeded:
fallthrough
case codes.Canceled:
if ctx.Err() != nil {
err = ctx.Err()
}
}
}
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
}
// IsConnCanceled returns true, if error is from a closed gRPC connection.
// ref. https://github.com/grpc/grpc-go/pull/1854
func IsConnCanceled(err error) bool {
if err == nil {
return false
}
// >= gRPC v1.23.x
s, ok := status.FromError(err)
if ok {
// connection is canceled or server has already closed the connection
return s.Code() == codes.Canceled || s.Message() == "transport is closing"
}
// >= gRPC v1.10.x
if err == context.Canceled {
return true
}
// <= gRPC v1.7.x returns 'errors.New("grpc: the client connection is closing")'
return strings.Contains(err.Error(), "grpc: the client connection is closing")
}
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