What causes "%s" in wtfutil/wtf?

Verify the UPDOWN token is set and valid (test with curl -H 'X-Api-Token: ...' https://updown.io/api/v1/checks)

%s

Error message

%s

What it means

Raised in getExistingChecks when the updown.io API returns a non-200 status: the error is only the HTTP status string (e.g. '401 Unauthorized'). Typical causes are an invalid X-API-KEY, exceeded rate limits, or updown.io service errors while listing existing checks.

Source

Thrown at modules/updown/widget.go:186

	// See: https://updown.io/api#rest
	u, err := makeURL(apiURLBase, "/api/checks")
	if err != nil {
		return nil, err
	}
	req, err := http.NewRequest("GET", u, http.NoBody)
	if err != nil {
		return nil, err
	}
	req.Header.Set("User-Agent", userAgent)
	req.Header.Set("X-API-KEY", widget.settings.apiKey)
	resp, err := http.DefaultClient.Do(req)

	if err != nil {
		return nil, err
	}

	if resp.StatusCode != 200 {
		return nil, fmt.Errorf("%s", resp.Status)
	}

	defer func() { _ = resp.Body.Close() }()

	var checks []Check
	err = utils.ParseJSON(&checks, resp.Body)
	if err != nil {
		return nil, err
	}

	if len(widget.tokenSet) > 0 {
		checks = filterChecks(checks, widget.tokenSet)
	}

	return checks, nil
}

View on GitHub (pinned to bb838c1ccb)

Solutions

Verify the UPDOWN token is set and valid (test with curl -H 'X-Api-Token: ...' https://updown.io/api/v1/checks)
Regenerate the token in the updown.io account settings if revoked
Retry later on 5xx/429
Confirm the widget is pointed at the current API base URL

Defensive patterns

Strategy: try-catch

Validate before calling

if apiKey == "" { return errors.New("updown API token not configured") }
tok := os.Getenv("UPDOWN_TOKEN")
if tok == "" { return errors.New("missing UPDOWN token") }

Try / catch

checks, err := w.getExistingChecks()
if err != nil {
    if strings.HasPrefix(err.Error(), "401") { log.Printf("updown auth failed; check token") }
    else { log.Printf("updown: %v", err) }
    return
}

Prevention

Store the API token in an environment variable and check it at startup
Test the token with curl against /api/v1/checks before deploying
Watch for 401 after rotating tokens in the updown dashboard
Back off on 429 rather than hammering the API

When it happens

Trigger: Any non-200 from updown.io /checks: 401 for invalid/missing UPDOWN_TOKEN, 404/410 for wrong API version path, 429 for rate limits, 5xx outages.

Common situations: Missing or revoked API token in config; token belonging to another account; updown.io API version changes; transient 5xx.

Related errors

AI-assisted analysis of wtfutil/wtf@bb838c1ccb (2026-09-03). Data as JSON: /api/errors/77508e3e073bc3e9. Report an issue: GitHub.