grafana/k6 · error

invalid output extension %s, built-in output with the same t

Error message

invalid output extension %s, built-in output with the same type already exists

What it means

Error "invalid output extension %s, built-in output with the same type already exists" thrown in grafana/k6.

Source

Thrown at internal/cmd/outputs.go:87

			return remotewrite.New(params)
		},
		"web-dashboard": dashboard.New,
		builtinOutputExperimentalOpentelemetry.String(): func(params output.Params) (output.Output, error) {
			params.Logger.Warnf("OpenTelemetry output has been graduated as a stable output."+
				"You can now use just %q instead of %q. The experimental version will be removed in future versions.",

				"opentelemetry", "experimental-opentelemetry")
			return opentelemetry.New(params)
		},
		builtinOutputOpentelemetry.String(): func(params output.Params) (output.Output, error) {
			return opentelemetry.New(params)
		},
	}

	exts := ext.Get(ext.OutputExtension)
	for _, e := range exts {
		if _, ok := result[e.Name]; ok {
			return nil, fmt.Errorf("invalid output extension %s, built-in output with the same type already exists", e.Name)
		}
		m, ok := e.Module.(output.Constructor)
		if !ok {
			return nil, fmt.Errorf("unexpected output extension type %T", e.Module)
		}
		result[e.Name] = m
	}

	return result, nil
}

func getPossibleIDList(constrs map[string]output.Constructor) string {
	res := make([]string, 0, len(constrs))
	for k := range constrs {
		if k == "kafka" || k == "datadog" {
			continue
		}
		res = append(res, k)

View on GitHub (pinned to 93accf6570)

When it happens

Trigger: Thrown at internal/cmd/outputs.go:87 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/a33df858978966dc. Report an issue: GitHub.