Golang Connection.Exists方法代码示例

// PathExists verifies if a path exists and does not raise an exception if the
// path does not exist
func PathExists(conn client.Connection, p string) (bool, error) {
	exists, err := conn.Exists(p)
	if err == client.ErrNoNode {
		return false, nil
	}
	return exists, err
}

func (s *Server) Run(shutdown <-chan interface{}, conn client.Connection) error {
	node := &Node{
		Host:       *s.host,
		ExportPath: fmt.Sprintf("%s:%s", s.host.IPAddr, s.driver.ExportPath()),
		ExportTime: strconv.FormatInt(time.Now().UnixNano(), 16),
	}

	// Create the storage leader and client nodes
	if exists, _ := conn.Exists("/storage/leader"); !exists {
		conn.CreateDir("/storage/leader")
	}

	storageClientsPath := "/storage/clients"

	if exists, _ := conn.Exists(storageClientsPath); !exists {
		conn.CreateDir(storageClientsPath)
	}

	leader := conn.NewLeader("/storage/leader", node)
	leaderW, err := leader.TakeLead()
	if err != zookeeper.ErrDeadlock && err != nil {
		glog.Errorf("Could not take storage lead: %s", err)
		return err
	}

	// monitor dfs; log warnings each cycle; restart dfs if needed
	go s.monitor.MonitorDFSVolume(path.Join("/exports", s.driver.ExportPath()), s.host.IPAddr, node.ExportTime, shutdown, s.monitor.DFSVolumeMonitorPollUpdateFunc)

	// loop until shutdown event
	defer leader.ReleaseLead()

	for {
		clients, clientW, err := conn.ChildrenW(storageClientsPath)
		if err != nil {
			glog.Errorf("Could not set up watch for storage clients: %s", err)
			return err
		}

		s.monitor.SetMonitorStorageClients(conn, storageClientsPath)
		s.driver.SetClients(clients...)
		if err := s.driver.Sync(); err != nil {
			glog.Errorf("Error syncing driver: %s", err)
			return err
		}

		select {
		case e := <-clientW:
			glog.Info("storage.server: receieved event: %s", e)
		case <-leaderW:
			err := fmt.Errorf("storage.server: lost lead")
			return err
		case <-shutdown:
			return nil
		}
	}
}

// updateInstance updates the service state and host instances
func updateInstance(conn client.Connection, hostID, stateID string, mutate func(*HostState, *ss.ServiceState)) error {
	glog.V(2).Infof("Updating instance %s", stateID)
	// do not lock if parent lock does not exist
	if exists, err := conn.Exists(path.Join(zkInstanceLock, stateID)); err != nil && err != client.ErrNoNode {
		glog.Errorf("Could not check for lock on instance %s: %s", stateID, err)
		return err
	} else if !exists {
		glog.Errorf("Lock not found for instance %s", stateID)
		return ErrLockNotFound
	}

	lock := newInstanceLock(conn, stateID)
	if err := lock.Lock(); err != nil {
		glog.Errorf("Could not set lock for service instance %s on host %s: %s", stateID, hostID, err)
		return err
	}
	defer lock.Unlock()
	glog.V(2).Infof("Acquired lock for instance %s", stateID)

	hpath := hostpath(hostID, stateID)
	var hsdata HostState
	if err := conn.Get(hpath, &hsdata); err != nil {
		glog.Errorf("Could not get instance %s for host %s: %s", stateID, hostID, err)
		return err
	}
	serviceID := hsdata.ServiceID
	spath := servicepath(serviceID, stateID)
	var ssnode ServiceStateNode
	if err := conn.Get(spath, &ssnode); err != nil {
		glog.Errorf("Could not get instance %s for service %s: %s", stateID, serviceID, err)
		return err
	}

	mutate(&hsdata, ssnode.ServiceState)

	if err := conn.Set(hpath, &hsdata); err != nil {
		glog.Errorf("Could not update instance %s for host %s: %s", stateID, hostID, err)
		return err
	}
	if err := conn.Set(spath, &ssnode); err != nil {
		glog.Errorf("Could not update instance %s for service %s: %s", stateID, serviceID, err)
		return err
	}
	glog.V(2).Infof("Releasing lock for instance %s", stateID)
	return nil
}