Method LabelValues

pkg/querier/querier.go:486–552

LabelValues implements storage.Querier.

(ctx context.Context, name string, hints *storage.LabelHints, matchers ...*labels.Matcher)

// LabelValues implements storage.Querier.
func (q querier) LabelValues(ctx context.Context, name string, hints *storage.LabelHints, matchers ...*labels.Matcher) ([]string, annotations.Annotations, error) {
	ctx, stats, userID, mint, maxt, metadataQuerier, queriers, err := q.setupFromCtx(ctx)
	if err == errEmptyTimeRange {
		return nil, nil, nil
	} else if err != nil {
		return nil, nil, err
	}
	startT := time.Now()
	defer func() {
		stats.AddQueryStorageWallTime(time.Since(startT))
	}()

	// For label values queries without specifying the start time, we prefer to
	// only query ingesters and not to query maxQueryLength to avoid OOM kill.
	if mint == 0 {
		return metadataQuerier.LabelValues(ctx, name, hints, matchers...)
	}

	startTime := model.Time(mint)
	endTime := model.Time(maxt)

	if maxQueryLength := q.limits.MaxQueryLength(userID); maxQueryLength > 0 && endTime.Sub(startTime) > maxQueryLength {
		limitErr := validation.LimitError(fmt.Sprintf(validation.ErrQueryTooLong, endTime.Sub(startTime), maxQueryLength))
		return nil, nil, limitErr
	}

	if len(queriers) == 1 {
		return queriers[0].LabelValues(ctx, name, hints, matchers...)
	}

	var (
		g, _     = errgroup.WithContext(ctx)
		sets     = [][]string{}
		warnings = annotations.Annotations(nil)

		resMtx sync.Mutex
	)

	for _, querier := range queriers {
		// Need to reassign as the original variable will change and can't be relied on in a goroutine.
		g.Go(func() error {
			// NB: Values are sorted in Cortex already.
			myValues, myWarnings, err := querier.LabelValues(ctx, name, hints, matchers...)
			if err != nil {
				return err
			}

			resMtx.Lock()
			sets = append(sets, myValues)
			warnings.Merge(myWarnings)
			resMtx.Unlock()

			return nil
		})
	}

	if err := g.Wait(); err != nil {
		return nil, nil, err