func Main() {
	cfg := NewConfig()
	err := cfg.Parse(os.Args[1:])
	if err != nil {
		plog.Errorf("error verifying flags, %v. See 'etcd --help'.", err)
		switch err {
		case errUnsetAdvertiseClientURLsFlag:
			plog.Errorf("When listening on specific address(es), this etcd process must advertise accessible url(s) to each connected client.")
		}
		os.Exit(1)
	}
	setupLogging(cfg)

	var stopped <-chan struct{}

	plog.Infof("etcd Version: %s\n", version.Version)
	plog.Infof("Git SHA: %s\n", version.GitSHA)
	plog.Infof("Go Version: %s\n", runtime.Version())
	plog.Infof("Go OS/Arch: %s/%s\n", runtime.GOOS, runtime.GOARCH)

	GoMaxProcs := runtime.GOMAXPROCS(0)
	plog.Infof("setting maximum number of CPUs to %d, total number of available CPUs is %d", GoMaxProcs, runtime.NumCPU())

	// TODO: check whether fields are set instead of whether fields have default value
	if cfg.name != defaultName && cfg.initialCluster == initialClusterFromName(defaultName) {
		cfg.initialCluster = initialClusterFromName(cfg.name)
	}

	if cfg.dir == "" {
		cfg.dir = fmt.Sprintf("%v.etcd", cfg.name)
		plog.Warningf("no data-dir provided, using default data-dir ./%s", cfg.dir)
	}

	which := identifyDataDirOrDie(cfg.dir)
	if which != dirEmpty {
		plog.Noticef("the server is already initialized as %v before, starting as etcd %v...", which, which)
		switch which {
		case dirMember:
			stopped, err = startEtcd(cfg)
		case dirProxy:
			err = startProxy(cfg)
		default:
			plog.Panicf("unhandled dir type %v", which)
		}
	} else {
		shouldProxy := cfg.isProxy()
		if !shouldProxy {
			stopped, err = startEtcd(cfg)
			if err == discovery.ErrFullCluster && cfg.shouldFallbackToProxy() {
				plog.Noticef("discovery cluster full, falling back to %s", fallbackFlagProxy)
				shouldProxy = true
			}
		}
		if shouldProxy {
			err = startProxy(cfg)
		}
	}

	if err != nil {
		switch err {
		case discovery.ErrDuplicateID:
			plog.Errorf("member %q has previously registered with discovery service token (%s).", cfg.name, cfg.durl)
			plog.Errorf("But etcd could not find valid cluster configuration in the given data dir (%s).", cfg.dir)
			plog.Infof("Please check the given data dir path if the previous bootstrap succeeded")
			plog.Infof("or use a new discovery token if the previous bootstrap failed.")
		case discovery.ErrDuplicateName:
			plog.Errorf("member with duplicated name has registered with discovery service token(%s).", cfg.durl)
			plog.Errorf("please check (cURL) the discovery token for more information.")
			plog.Errorf("please do not reuse the discovery token and generate a new one to bootstrap the cluster.")
		default:
			if strings.Contains(err.Error(), "include") && strings.Contains(err.Error(), "--initial-cluster") {
				plog.Infof("%v", err)
				if cfg.initialCluster == initialClusterFromName(cfg.name) {
					plog.Infof("forgot to set --initial-cluster flag?")
				}
				if types.URLs(cfg.apurls).String() == defaultInitialAdvertisePeerURLs {
					plog.Infof("forgot to set --initial-advertise-peer-urls flag?")
				}
				if cfg.initialCluster == initialClusterFromName(cfg.name) && len(cfg.durl) == 0 {
					plog.Infof("if you want to use discovery service, please set --discovery flag.")
				}
				os.Exit(1)
			}
			if etcdserver.IsDiscoveryError(err) {
				plog.Errorf("%v", err)
				plog.Infof("discovery token %s was used, but failed to bootstrap the cluster.", cfg.durl)
				plog.Infof("please generate a new discovery token and try to bootstrap again.")
				os.Exit(1)
			}
			plog.Fatalf("%v", err)
		}
		os.Exit(1)
	}

	osutil.HandleInterrupts()

	if systemdutil.IsRunningSystemd() {
		// At this point, the initialization of etcd is done.
		// The listeners are listening on the TCP ports and ready
		// for accepting connections.
//.........这里部分代码省略.........

func Main() {
	capnslog.SetFormatter(capnslog.NewStringFormatter(os.Stderr))
	cfg := NewConfig()
	err := cfg.Parse(os.Args[1:])
	if err != nil {
		plog.Errorf("error verifying flags, %v. See 'etcd --help'.", err)
		switch err {
		case errUnsetAdvertiseClientURLsFlag:
			plog.Errorf("When listening on specific address(es), this etcd process must advertise accessible url(s) to each connected client.")
		}
		os.Exit(1)
	}
	setupLogging(cfg)

	var stopped <-chan struct{}

	GoMaxProcs := 1
	if envMaxProcs, err := strconv.Atoi(os.Getenv("GOMAXPROCS")); err == nil {
		GoMaxProcs = envMaxProcs
	}
	plog.Infof("setting maximum number of CPUs to %d, total number of available CPUs is %d", GoMaxProcs, runtime.NumCPU())
	runtime.GOMAXPROCS(GoMaxProcs)

	// TODO: check whether fields are set instead of whether fields have default value
	if cfg.name != defaultName && cfg.initialCluster == initialClusterFromName(defaultName) {
		cfg.initialCluster = initialClusterFromName(cfg.name)
	}

	if cfg.dir == "" {
		cfg.dir = fmt.Sprintf("%v.etcd", cfg.name)
		plog.Warningf("no data-dir provided, using default data-dir ./%s", cfg.dir)
	}

	which := identifyDataDirOrDie(cfg.dir)
	if which != dirEmpty {
		plog.Noticef("the server is already initialized as %v before, starting as etcd %v...", which, which)
	}

	shouldProxy := cfg.isProxy() || which == dirProxy
	if !shouldProxy {
		stopped, err = startEtcd(cfg)
		if err == discovery.ErrFullCluster && cfg.shouldFallbackToProxy() {
			plog.Noticef("discovery cluster full, falling back to %s", fallbackFlagProxy)
			shouldProxy = true
		}
	}
	if shouldProxy {
		err = startProxy(cfg)
	}
	if err != nil {
		switch err {
		case discovery.ErrDuplicateID:
			plog.Errorf("member %q has previously registered with discovery service token (%s).", cfg.name, cfg.durl)
			plog.Errorf("But etcd could not find vaild cluster configuration in the given data dir (%s).", cfg.dir)
			plog.Infof("Please check the given data dir path if the previous bootstrap succeeded")
			plog.Infof("or use a new discovery token if the previous bootstrap failed.")
			os.Exit(1)
		default:
			plog.Fatalf("%v", err)
		}
	}

	osutil.HandleInterrupts()

	<-stopped
	osutil.Exit(0)
}