hashicorp/nomad · error

failed to generate logging UI

Error message

failed to generate logging UI

What it means

NewLogUI builds the logging UI (mitchellh/cli-based) used by `nomad ui` logging-related commands. It succeeds if it can wire either a colorized or basic UI from the provided options; if none of the known UI flavors could be constructed (the `found` flag stays false), it returns this error.

Source

Thrown at command/ui/log_ui.go:70

		logUI.warnColor = coloredUI.WarnColor
		logUI.underlyingUI = coloredUI.Ui

		if basicUI, ok := coloredUI.Ui.(*cli.BasicUi); ok {
			logUI.reader = basicUI.Reader
			logUI.writer = basicUI.Writer
			logUI.errorWriter = basicUI.ErrorWriter
			found = true
		}
	} else if basicUI, ok := ui.(*cli.BasicUi); ok && !found {
		logUI.reader = basicUI.Reader
		logUI.writer = basicUI.Writer
		logUI.errorWriter = basicUI.ErrorWriter
		logUI.underlyingUI = basicUI
		found = true
	}

	if !found {
		return nil, errors.New("failed to generate logging UI")
	}

	return &logUI, nil
}

// Ask implements the Ask function of the cli.Ui interface.
func (l *LogUI) Ask(query string) (string, error) {
	return l.underlyingUI.Ask(l.colorize(query, l.outputColor))
}

// AskSecret implements the AskSecret function of the cli.Ui interface.
func (l *LogUI) AskSecret(query string) (string, error) {
	return l.underlyingUI.AskSecret(l.colorize(query, l.outputColor))
}

// Output implements the Output function of the cli.Ui interface.
func (l *LogUI) Output(message string) {
	_, _ = fmt.Fprint(l.writer, l.colorize(message, l.outputColor))

View on GitHub (pinned to 482b49bf1a)

Solutions

1. Pass a valid, non-nil configuration: ensure the input/output/error writers (or a supported underlying cli.Ui) are provided so one of the code paths sets found=true.
2. Use a plain basic UI (cli.NewBasicUi) as fallback input so at least the basic path succeeds.
3. Update Nomad if hitting this with options that should be supported; check for regressions in ui/log_ui.go.

Example fix

// before
logUI, err := NewLogUI(nil) // no usable UI options
// after
basicUI := cli.NewBasicUi(cli.BasicUiOpts{Writer: os.Stdout, ErrorWriter: os.Stderr})
logUI, err := NewLogUI(basicUI)

if uiOpts == nil || (uiOpts.Writer == nil && uiOpts.ErrorWriter == nil) {
    return errors.New("LogUI requires valid writer options")
}

func canBuildLogUI(o *LogUIOptions) bool { return o != nil && (o.Writer != nil || o.UnderlyingUI != nil) }

logUI, err := NewLogUI(opts)
if err != nil && strings.Contains(err.Error(), "failed to generate logging UI") {
    logUI = cli.NewBasicUi(cli.BasicUiOpts{Writer: os.Stdout, ErrorWriter: os.Stderr})
}

When it happens

Trigger: Calling NewLogUI with a configuration that matches neither the colorized nor the basic UI path — e.g. nil/invalid CLI options or UI configuration leaving no supported underlying UI available.

Common situations: Programmatic callers constructing the UI with incomplete cli.Ui options; embedding nomad command code with non-standard writers; misconfigured nomad UI setup.

Related errors

• failed to generate command UI
• Unknown log level
• No nomad log file defined
• eventlog.level must be one of INFO, WARN, or ERROR
• no default Consul services client

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/774a8351ca64bc83. Report an issue: GitHub.