Function getTimeFromServer

internal/clock/now_testing.go:36–77

getTimeFromServer returns a function that will return timestamp as returned by the server increasing it client-side by certain interval until maximum is reached, at which point it will ask the server again for new timestamp. The server endpoint must be HTTP and be set using KOPIA_FAKE_CLOCK_ENDPOIN

(endpoint string)

// The server endpoint must be HTTP and be set using KOPIA_FAKE_CLOCK_ENDPOINT environment
// variable.
func getTimeFromServer(endpoint string) func() time.Time {
	var mu sync.Mutex

	var timeInfo struct {
		Time     time.Time     `json:"time"`
		ValidFor time.Duration `json:"validFor"`
	}

	var (
		nextRefreshRealTime time.Time     //nolint:forbidigo
		localTimeOffset     time.Duration // offset to be added to time.Now() to produce server time
	)

	return func() time.Time {
		mu.Lock()
		defer mu.Unlock()

		localTime := time.Now() //nolint:forbidigo
		if localTime.After(nextRefreshRealTime) {
			resp, err := http.Get(endpoint) //nolint:gosec,noctx
			if err != nil {
				log.Fatalf("unable to get fake time from server: %v", err)
			}
			defer resp.Body.Close() //nolint:errcheck

			if resp.StatusCode != http.StatusOK {
				log.Fatalf("unable to get fake time from server: %v", resp.Status)
			}

			if err := json.NewDecoder(resp.Body).Decode(&timeInfo); err != nil {
				log.Fatalf("invalid time received from fake time server: %v", err)
			}

			nextRefreshRealTime = localTime.Add(timeInfo.ValidFor) //nolint:forbidigo

			// compute offset such that localTime + localTimeOffset == serverTime
			localTimeOffset = timeInfo.Time.Sub(localTime)
		}

		return discardMonotonicTime(localTime.Add(localTimeOffset))
	}
}