func (s *Snapshotter) save(snapshot *raftpb.Snapshot) error {
	start := time.Now()

	fname := fmt.Sprintf("%016x-%016x%s", snapshot.Metadata.Term, snapshot.Metadata.Index, snapSuffix)
	b := pbutil.MustMarshal(snapshot)
	crc := crc32.Update(0, crcTable, b)
	snap := snappb.Snapshot{Crc: crc, Data: b}
	d, err := snap.Marshal()
	if err != nil {
		return err
	} else {
		marshallingDurations.Observe(float64(time.Since(start)) / float64(time.Second))
	}

	err = pioutil.WriteAndSyncFile(path.Join(s.dir, fname), d, 0666)
	if err == nil {
		saveDurations.Observe(float64(time.Since(start)) / float64(time.Second))
	} else {
		err1 := os.Remove(path.Join(s.dir, fname))
		if err1 != nil {
			plog.Errorf("failed to remove broken snapshot file %s", path.Join(s.dir, fname))
		}
	}
	return err
}

// startProxy launches an HTTP proxy for client communication which proxies to other etcd nodes.
func startProxy(cfg *config) error {
	plog.Notice("proxy: this proxy supports v2 API only!")

	pt, err := transport.NewTimeoutTransport(cfg.PeerTLSInfo, time.Duration(cfg.ProxyDialTimeoutMs)*time.Millisecond, time.Duration(cfg.ProxyReadTimeoutMs)*time.Millisecond, time.Duration(cfg.ProxyWriteTimeoutMs)*time.Millisecond)
	if err != nil {
		return err
	}
	pt.MaxIdleConnsPerHost = httpproxy.DefaultMaxIdleConnsPerHost

	tr, err := transport.NewTimeoutTransport(cfg.PeerTLSInfo, time.Duration(cfg.ProxyDialTimeoutMs)*time.Millisecond, time.Duration(cfg.ProxyReadTimeoutMs)*time.Millisecond, time.Duration(cfg.ProxyWriteTimeoutMs)*time.Millisecond)
	if err != nil {
		return err
	}

	cfg.Dir = path.Join(cfg.Dir, "proxy")
	err = os.MkdirAll(cfg.Dir, fileutil.PrivateDirMode)
	if err != nil {
		return err
	}

	var peerURLs []string
	clusterfile := path.Join(cfg.Dir, "cluster")

	b, err := ioutil.ReadFile(clusterfile)
	switch {
	case err == nil:
		if cfg.Durl != "" {
			plog.Warningf("discovery token ignored since the proxy has already been initialized. Valid cluster file found at %q", clusterfile)
		}
		if cfg.DNSCluster != "" {
			plog.Warningf("DNS SRV discovery ignored since the proxy has already been initialized. Valid cluster file found at %q", clusterfile)
		}
		urls := struct{ PeerURLs []string }{}
		err = json.Unmarshal(b, &urls)
		if err != nil {
			return err
		}
		peerURLs = urls.PeerURLs
		plog.Infof("proxy: using peer urls %v from cluster file %q", peerURLs, clusterfile)
	case os.IsNotExist(err):
		var urlsmap types.URLsMap
		urlsmap, _, err = cfg.PeerURLsMapAndToken("proxy")
		if err != nil {
			return fmt.Errorf("error setting up initial cluster: %v", err)
		}

		if cfg.Durl != "" {
			var s string
			s, err = discovery.GetCluster(cfg.Durl, cfg.Dproxy)
			if err != nil {
				return err
			}
			if urlsmap, err = types.NewURLsMap(s); err != nil {
				return err
			}
		}
		peerURLs = urlsmap.URLs()
		plog.Infof("proxy: using peer urls %v ", peerURLs)
	default:
		return err
	}

	clientURLs := []string{}
	uf := func() []string {
		gcls, gerr := etcdserver.GetClusterFromRemotePeers(peerURLs, tr)

		if gerr != nil {
			plog.Warningf("proxy: %v", gerr)
			return []string{}
		}

		clientURLs = gcls.ClientURLs()

		urls := struct{ PeerURLs []string }{gcls.PeerURLs()}
		b, jerr := json.Marshal(urls)
		if jerr != nil {
			plog.Warningf("proxy: error on marshal peer urls %s", jerr)
			return clientURLs
		}

		err = pkgioutil.WriteAndSyncFile(clusterfile+".bak", b, 0600)
		if err != nil {
			plog.Warningf("proxy: error on writing urls %s", err)
			return clientURLs
		}
		err = os.Rename(clusterfile+".bak", clusterfile)
		if err != nil {
			plog.Warningf("proxy: error on updating clusterfile %s", err)
			return clientURLs
		}
		if !reflect.DeepEqual(gcls.PeerURLs(), peerURLs) {
			plog.Noticef("proxy: updated peer urls in cluster file from %v to %v", peerURLs, gcls.PeerURLs())
		}
		peerURLs = gcls.PeerURLs()

		return clientURLs
	}
	ph := httpproxy.NewHandler(pt, uf, time.Duration(cfg.ProxyFailureWaitMs)*time.Millisecond, time.Duration(cfg.ProxyRefreshIntervalMs)*time.Millisecond)
	ph = &cors.CORSHandler{
//.........这里部分代码省略.........