grafana/k6 · error

invalid DNS TTL: %s

Error message

invalid DNS TTL: %s

What it means

Root error from parseTTL: the ttl string failed ParseExtendedDuration or parsed to a negative duration. Valid inputs are exactly '0' (cache disabled), 'inf' (cached ~1 year), '' (falls back to k6's default '1m'), or a single non-negative duration like '300s'/'5m'/'1h'. Comma-separated TTL lists are NOT supported in the browser module even though k6's HTTP stack accepts them.

Source

Thrown at internal/js/modules/k6/browser/common/network_manager.go:201

// Parse a string representation of TTL to time.Duration.
// Copied from https://github.com/grafana/k6/blob/fb70bc6f3d3f22a40e65f32deea3cea1b6d70a76/js/runner.go#L479
func parseTTL(ttlS string) (time.Duration, error) {
	ttl := time.Duration(0)
	switch ttlS {
	case "inf":
		// cache "infinitely"
		ttl = time.Hour * 24 * 365
	case "0":
		// disable cache
	case "":
		ttlS = k6types.DefaultDNSConfig().TTL.String
		fallthrough
	default:
		var err error
		ttl, err = k6types.ParseExtendedDuration(ttlS)
		if ttl < 0 || err != nil {
			return ttl, fmt.Errorf("invalid DNS TTL: %s", ttlS)
		}
	}
	return ttl, nil
}

func (m *NetworkManager) deleteRequestByID(reqID network.RequestID) {
	m.reqsMu.Lock()
	defer m.reqsMu.Unlock()
	delete(m.reqIDToRequest, reqID)
}

func (m *NetworkManager) emitRequestMetrics(req *Request) {
	state := m.vu.State()

	tags := state.Tags.GetCurrentValues().Tags
	if state.Options.SystemTags.Has(k6metrics.TagMethod) {
		tags = tags.With("method", req.method)
	}

View on GitHub (pinned to 93accf6570)

Solutions

1. Use a single valid duration: '1m', '300s', '1h', or '0'/'inf'
2. Never pass a comma list to dns.ttl in scripts that use the browser module
3. Sanity-check generated/templated options before running
4. If you need per-lookup TTL variety, keep it in HTTP-only scenarios and override dns.ttl for browser scenarios

Example fix

// before
export const options = { dns: { ttl: '60s,10m' } };

// after
export const options = { dns: { ttl: '60s' } };

const ttl = '60s';
if (!/^(0|inf|\d+(\.\d+)?(ms|s|m|h))$/.test(ttl)) {
  throw new Error(`dns.ttl '${ttl}' invalid; use 0, inf, or a single duration`);
}

function isValidTtlString(s) {
  if (s === '' || s === '0' || s === 'inf') return true;
  return /^\d+(\.\d+)?(ms|s|m|h)$/.test(s); // no commas, no negatives
}

When it happens

Trigger: dns.ttl set to 'abc', '1hr', '-1m', or '60s,5m'. Empty string is fine (default applied); '0' and 'inf' are special-cased; everything else must parse as one non-negative duration.

Common situations: Sharing one options object between HTTP and browser scenarios where the HTTP side uses a TTL list; hand-edited durations with wrong units; negative values from templating bugs.

Related errors

• newResolver(%+v): %w
• parsing TTL: %w
• predicate function is not callable
• "handler" argument cannot be nil
• clip area is either empty or outside the viewport

AI-assisted analysis of grafana/k6@93accf6570 (2026-08-15). Data as JSON: /api/errors/85c59961a9015282. Report an issue: GitHub.