grafana/k6 · error

unsupported log output '%s'

Error message

unsupported log output '%s'

What it means

Error "unsupported log output '%s'" thrown in grafana/k6.

Source

Thrown at internal/cmd/root.go:388

	case line == "none":
		c.globalState.Logger.SetOutput(io.Discard)
	case strings.HasPrefix(line, "loki"):
		c.loggerIsRemote = true
		hook, err = log.LokiFromConfigLine(c.globalState.FallbackLogger, line)
		if err != nil {
			return err
		}
		c.globalState.Flags.LogFormat = "raw"
	case strings.HasPrefix(line, "file"):
		hook, err = log.FileHookFromConfigLine(
			c.globalState.FS, c.globalState.Getwd,
			c.globalState.FallbackLogger, line,
		)
		if err != nil {
			return err
		}
	default:
		return fmt.Errorf("unsupported log output '%s'", line)
	}

	switch c.globalState.Flags.LogFormat {
	case "raw":
		c.globalState.Logger.SetFormatter(&RawFormatter{})
		c.globalState.Logger.Debug("Logger format: RAW")
	case "json":
		c.globalState.Logger.SetFormatter(&logrus.JSONFormatter{})
		c.globalState.Logger.Debug("Logger format: JSON")
	default:
		c.globalState.Logger.SetFormatter(&logrus.TextFormatter{
			ForceColors: loggerForceColors, DisableColors: c.globalState.Flags.NoColor,
		})
		c.globalState.Logger.Debug("Logger format: TEXT")
	}

	secretsources, err := createSecretSources(c.globalState)
	if err != nil {

View on GitHub (pinned to 93accf6570)

When it happens

Trigger: Thrown at internal/cmd/root.go:388 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of grafana/k6@93accf6570 (2026-08-15). Data as JSON: /api/errors/4d67b1a5b7c4e122. Report an issue: GitHub.