grafana/k6 · error

got status code: %d instead expected a 2xx successful status

Error message

got status code: %d instead expected a 2xx successful status code

What it means

The Prometheus remote write endpoint answered the POST with a non-2xx HTTP status. validateResponseStatus treats anything outside 200–299 as a failed write; the code indicates the server's rejection reason (400 bad payload, 401 auth, 5xx server error, etc.).

Source

Thrown at internal/output/prometheusrw/remote/client.go:141

	b, err := proto.Marshal(&prompb.WriteRequest{
		Timeseries: series,
	})
	if err != nil {
		return nil, fmt.Errorf("encoding series as protobuf write request failed: %w", err)
	}
	if snappy.MaxEncodedLen(len(b)) < 0 {
		return nil, fmt.Errorf("the protobuf message is too large to be handled by Snappy encoder; "+
			"size: %d, limit: %d", len(b), math.MaxUint32)
	}
	return snappy.Encode(nil, b), nil
}

func validateResponseStatus(code int) error {
	if code >= http.StatusOK && code < 300 {
		return nil
	}

	return fmt.Errorf("got status code: %d instead expected a 2xx successful status code", code)
}

View on GitHub (pinned to 01ffac6f24)

Solutions

1. Look up the status code: 401/403 means fix basic auth credentials; 400 means payload/labels rejected; 5xx means check Prometheus health
2. Verify remote_write receiver is enabled on the Prometheus server
3. Check for invalid label names/values produced by the script

When it happens

Trigger: Thrown at internal/output/prometheusrw/remote/client.go:141 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/b7c4b3783e2ae502. Report an issue: GitHub.