func (f *fileInfo) WaitForChange(running *sync2.AtomicInt32) error {
	for {
		if running.Get() != 1 {
			return io.EOF
		}
		time.Sleep(100 * time.Millisecond)
		fi, err := f.handle.Stat()
		if err != nil {
			return fmt.Errorf("stat error: %v", err)
		}
		if fi.Size() != f.pos {
			return nil
		}
	}
}

// qps is a function used by tests to run a vtgate load check.
// It will get the same srvKeyspaces as fast as possible and display the QPS.
func qps(ctx context.Context, cell string, keyspaces []string) {
	var count sync2.AtomicInt32
	for _, keyspace := range keyspaces {
		for i := 0; i < 10; i++ {
			go func() {
				rpcClient := connect()
				for true {
					getSrvKeyspace(ctx, rpcClient, cell, keyspace, false)
					count.Add(1)
				}
			}()
		}
	}

	ticker := time.NewTicker(time.Second)
	i := 0
	for _ = range ticker.C {
		c := count.Get()
		count.Set(0)
		println(fmt.Sprintf("QPS = %v", c))
		i++
		if i == 10 {
			break
		}
	}
}

// qps is a function used by tests to run a zkocc load check.
// It will get zk paths as fast as possible and display the QPS.
func qps(paths []string) {
	var count sync2.AtomicInt32
	for _, path := range paths {
		for i := 0; i < 10; i++ {
			go func() {
				rpcClient := connect()
				for true {
					get(rpcClient, path, false)
					count.Add(1)
				}
			}()
		}
	}

	ticker := time.NewTicker(time.Second)
	i := 0
	for _ = range ticker.C {
		c := count.Get()
		count.Set(0)
		println(fmt.Sprintf("QPS = %v", c))
		i++
		if i == 10 {
			break
		}
	}
}

func commandPruneActionLogs(wr *wrangler.Wrangler, subFlags *flag.FlagSet, args []string) error {
	keepCount := subFlags.Int("keep-count", 10, "count to keep")
	if err := subFlags.Parse(args); err != nil {
		return err
	}

	if subFlags.NArg() == 0 {
		return fmt.Errorf("action PruneActionLogs requires <zk action log path> ...")
	}

	paths, err := resolveWildcards(wr, subFlags.Args())
	if err != nil {
		return err
	}

	zkts, ok := wr.TopoServer().(*zktopo.Server)
	if !ok {
		return fmt.Errorf("PruneActionLogs requires a zktopo.Server")
	}

	var errCount sync2.AtomicInt32
	wg := sync.WaitGroup{}
	for _, zkActionLogPath := range paths {
		wg.Add(1)
		go func(zkActionLogPath string) {
			defer wg.Done()
			purgedCount, err := zkts.PruneActionLogs(zkActionLogPath, *keepCount)
			if err == nil {
				wr.Logger().Infof("%v pruned %v", zkActionLogPath, purgedCount)
			} else {
				wr.Logger().Errorf("%v pruning failed: %v", zkActionLogPath, err)
				errCount.Add(1)
			}
		}(zkActionLogPath)
	}
	wg.Wait()
	if errCount.Get() > 0 {
		return fmt.Errorf("some errors occurred, check the log")
	}
	return nil
}

func commandStaleActions(wr *wrangler.Wrangler, subFlags *flag.FlagSet, args []string) (string, error) {
	maxStaleness := subFlags.Duration("max-staleness", 5*time.Minute, "how long since the last modification before an action considered stale")
	purge := subFlags.Bool("purge", false, "purge stale actions")
	if err := subFlags.Parse(args); err != nil {
		return "", err
	}
	if subFlags.NArg() == 0 {
		return "", fmt.Errorf("action StaleActions requires <zk action path>")
	}
	zkts, ok := wr.TopoServer().(*zktopo.Server)
	if !ok {
		return "", fmt.Errorf("StaleActions requires a zktopo.Server")
	}
	zkPaths, err := resolveWildcards(wr, subFlags.Args())
	if err != nil {
		return "", err
	}
	var errCount sync2.AtomicInt32
	wg := sync.WaitGroup{}
	for _, apath := range zkPaths {
		wg.Add(1)
		go func(zkActionPath string) {
			defer wg.Done()
			staleActions, err := staleActions(zkts, zkActionPath, *maxStaleness)
			if err != nil {
				errCount.Add(1)
				wr.Logger().Errorf("can't check stale actions: %v %v", zkActionPath, err)
				return
			}
			for _, action := range staleActions {
				wr.Logger().Printf("%v\n", fmtAction(action))
			}
			if *purge && len(staleActions) > 0 {
				err := zkts.PurgeActions(zkActionPath, actionnode.ActionNodeCanBePurged)
				if err != nil {
					errCount.Add(1)
					wr.Logger().Errorf("can't purge stale actions: %v %v", zkActionPath, err)
					return
				}
			}
		}(apath)
	}
	wg.Wait()
	if errCount.Get() > 0 {
		return "", fmt.Errorf("some errors occurred, check the log")
	}
	return "", nil
}