grafana/k6 · error

got %d from loki: %s

Error message

got %d from loki: %s

What it means

The Loki push endpoint returned an HTTP status code of 400 or higher; the response body is included verbatim. This indicates the Loki server rejected the batch of log entries (bad payload, auth failure, rate limit, or server error).

Source

Thrown at internal/log/loki.go:466

		return err
	}
	req.GetBody = func() (io.ReadCloser, error) {
		return io.NopCloser(bytes.NewBuffer(body)), nil
	}

	req.Header.Set("Content-Type", "application/json")

	for _, header := range h.headers {
		req.Header.Add(header[0], header[1])
	}

	res, err := h.client.Do(req) //nolint:gosec

	if res != nil {
		if res.StatusCode >= 400 {
			r, _ := io.ReadAll(res.Body) // maybe limit it to something like the first 1000 characters?

			return fmt.Errorf("got %d from loki: %s", res.StatusCode, string(r))
		}
		_, _ = io.Copy(io.Discard, res.Body)
		_ = res.Body.Close()
	}

	return err
}

func mapEqual(a, b map[string]string) bool {
	if len(a) != len(b) {
		return false
	}
	for k, v := range a {
		if v2, ok := b[k]; !ok || v2 != v {
			return false
		}
	}

View on GitHub (pinned to 01ffac6f24)

Solutions

1. Inspect the response body in the error for the Loki server's reason
2. Verify the Loki address and credentials/headers are correct
3. Reduce msgMaxSize or batch volume if payloads are too large
4. Check Loki server health and rate limits

When it happens

Trigger: Thrown at internal/log/loki.go:466 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of grafana/k6@01ffac6f24 (2026-08-18). Data as JSON: /api/errors/b86d42f99717dccf. Report an issue: GitHub.