Golang Client.Watch方法代碼示例

func WaitPrefixEvents(c *clientv3.Client, prefix string, rev int64, evs []mvccpb.Event_EventType) (*clientv3.Event, error) {
	wc := c.Watch(context.Background(), prefix, clientv3.WithPrefix(), clientv3.WithRev(rev))
	if wc == nil {
		return nil, ErrNoWatcher
	}
	return waitEvents(wc, evs), nil
}

// WaitEvents waits on a key until it observes the given events and returns the final one.
func WaitEvents(c *clientv3.Client, key string, rev int64, evs []storagepb.Event_EventType) (*storagepb.Event, error) {
	wc := c.Watch(context.Background(), key, clientv3.WithRev(rev))
	if wc == nil {
		return nil, ErrNoWatcher
	}
	return waitEvents(wc, evs), nil
}

func waitUpdate(ctx context.Context, client *v3.Client, key string, opts ...v3.OpOption) error {
	cctx, cancel := context.WithCancel(ctx)
	defer cancel()
	wresp, ok := <-client.Watch(cctx, key, opts...)
	if !ok {
		return ctx.Err()
	}
	return wresp.Err()
}

// snapshotToStdout streams a snapshot over stdout
func snapshotToStdout(c *clientv3.Client) {
	// must explicitly fetch first revision since no retry on stdout
	wr := <-c.Watch(context.TODO(), "", clientv3.WithPrefix(), clientv3.WithRev(1))
	if wr.Err() == nil {
		wr.CompactRevision = 1
	}
	if rev := snapshot(os.Stdout, c, wr.CompactRevision+1); rev != 0 {
		err := fmt.Errorf("snapshot interrupted by compaction %v", rev)
		ExitWithError(ExitInterrupted, err)
	}
	os.Stdout.Sync()
}

func waitDelete(ctx context.Context, client *v3.Client, key string, rev int64) error {
	cctx, cancel := context.WithCancel(ctx)
	defer cancel()
	wch := client.Watch(cctx, key, v3.WithRev(rev))
	for wr := range wch {
		for _, ev := range wr.Events {
			if ev.Type == storagepb.DELETE {
				return nil
			}
		}
	}
	if err := ctx.Err(); err != nil {
		return err
	}
	return fmt.Errorf("lost watcher waiting for delete")
}

func getWatchChan(c *clientv3.Client, args []string) (clientv3.WatchChan, error) {
	if len(args) < 1 || len(args) > 2 {
		return nil, fmt.Errorf("bad number of arguments")
	}
	key := args[0]
	opts := []clientv3.OpOption{clientv3.WithRev(watchRev)}
	if len(args) == 2 {
		if watchPrefix {
			return nil, fmt.Errorf("`range_end` and `--prefix` are mutually exclusive")
		}
		opts = append(opts, clientv3.WithRange(args[1]))
	}
	if watchPrefix {
		opts = append(opts, clientv3.WithPrefix())
	}
	if watchPrevKey {
		opts = append(opts, clientv3.WithPrevKV())
	}
	return c.Watch(context.TODO(), key, opts...), nil
}

func etcdMon_v3(prefix string, c3 *clientv3.Client, bus chan fileChangeEvent, startRevision int64) {
	key, option := prefixToKeyOption(prefix)
	ch := c3.Watch(context.Background(), key, option, clientv3.WithRev(startRevision))
	for chEvent := range ch {
		for _, event := range chEvent.Events {
			fileEvent := fileChangeEvent{
				Path:    string(event.Kv.Key),
				Content: event.Kv.Value,
			}
			switch event.Type {
			case mvccpb.PUT:
				bus <- fileEvent
			case mvccpb.DELETE:
				fileEvent.IsRemoved = true
				bus <- fileEvent
			default:
				log.Println("etcdMon_v3 undefined event type: ", event.Type)
			}
		}
	}
	close(bus)
}

func main() {
	flag.Parse()

	if config.Version {
		fmt.Printf("skydns server version: %s\n", server.Version)
		os.Exit(0)
	}

	machines := strings.Split(machine, ",")

	var clientptr *etcdv3.Client
	var err error
	var clientv3 etcdv3.Client
	var clientv2 etcd.KeysAPI

	if config.Etcd3 {
		clientptr, err = newEtcdV3Client(machines, tlspem, tlskey, cacert)
		clientv3 = *clientptr
	} else {
		clientv2, err = newEtcdV2Client(machines, tlspem, tlskey, cacert, username, password)
	}

	if err != nil {
		panic(err)
	}

	if nameserver != "" {
		for _, hostPort := range strings.Split(nameserver, ",") {
			if err := validateHostPort(hostPort); err != nil {
				log.Fatalf("skydns: nameserver is invalid: %s", err)
			}
			config.Nameservers = append(config.Nameservers, hostPort)
		}
	}
	if err := validateHostPort(config.DnsAddr); err != nil {
		log.Fatalf("skydns: addr is invalid: %s", err)
	}

	if config.Etcd3 {
		if err := loadEtcdV3Config(clientv3, config); err != nil {
			log.Fatalf("skydns: %s", err)
		}
	} else {
		if err := loadEtcdV2Config(clientv2, config); err != nil {
			log.Fatalf("skydns: %s", err)
		}
	}

	if err := server.SetDefaults(config); err != nil {
		log.Fatalf("skydns: defaults could not be set from /etc/resolv.conf: %v", err)
	}

	if config.Local != "" {
		config.Local = dns.Fqdn(config.Local)
	}

	var backend server.Backend
	if config.Etcd3 {
		backend = backendetcdv3.NewBackendv3(clientv3, ctx, &backendetcdv3.Config{
			Ttl:      config.Ttl,
			Priority: config.Priority,
		})
	} else {
		backend = backendetcd.NewBackend(clientv2, ctx, &backendetcd.Config{
			Ttl:      config.Ttl,
			Priority: config.Priority,
		})
	}

	s := server.New(backend, config)
	if stub {
		s.UpdateStubZones()
		go func() {
			duration := 1 * time.Second

			if config.Etcd3 {
				var watcher etcdv3.WatchChan
				watcher = clientv3.Watch(ctx, msg.Path(config.Domain)+"/dns/stub/", etcdv3.WithPrefix())

				for wresp := range watcher {
					if wresp.Err() != nil {
						log.Printf("skydns: stubzone update failed, sleeping %s + ~3s", duration)
						time.Sleep(duration + (time.Duration(rand.Float32() * 3e9)))
						duration *= 2
						if duration > 32*time.Second {
							duration = 32 * time.Second
						}
					} else {
						s.UpdateStubZones()
						log.Printf("skydns: stubzone update")
						duration = 1 * time.Second //reset
					}
				}
			} else {
				var watcher etcd.Watcher

				watcher = clientv2.Watcher(msg.Path(config.Domain)+"/dns/stub/", &etcd.WatcherOptions{AfterIndex: 0, Recursive: true})

				for {
					_, err := watcher.Next(ctx)
//.........這裏部分代碼省略.........