glanceapp/glance · error

parsing URL: %w

Error message

parsing URL: %w

What it means

url.Parse failed on the widget source when it starts with tcp:// or http://. Practically this only happens for malformed URLs, since Go's parser is lenient (it does not validate scheme-legal characters strictly here). The parsed result is used to build host:port for the Docker API connection.

Source

Thrown at internal/glance/widget-docker-containers.go:295

	return hideByDefault
}


func fetchDockerContainersFromSource(
	source string,
	category string,
	runningOnly bool,
	labelOverrides map[string]map[string]string,
) ([]dockerContainerJsonResponse, error) {
	var hostname string

	var client *http.Client
	if strings.HasPrefix(source, "tcp://") || strings.HasPrefix(source, "http://") {
		client = &http.Client{}
		parsed, err := url.Parse(source)
		if err != nil {
			return nil, fmt.Errorf("parsing URL: %w", err)
		}

		port := parsed.Port()
		if port == "" {
			port = "80"
		}

		hostname = parsed.Hostname() + ":" + port
	} else {
		hostname = "docker"
		client = &http.Client{
			Transport: &http.Transport{
				DialContext: func(_ context.Context, _, _ string) (net.Conn, error) {
					return net.Dial("unix", source)
				},
			},
		}
	}

View on GitHub (pinned to 91324e8de7)

Solutions

1. Quote the source value in YAML
2. Check for spaces, brackets, or control characters in the tcp:// URL
3. Test the URL with a Go snippet or use a known-good value like tcp://host:2375

Example fix

# before
  host: tcp://docker host:2375
# after
  host: "tcp://docker-host:2375"

func validateDockerSource(src string) error {
    if strings.HasPrefix(src, "tcp://") || strings.HasPrefix(src, "http://") {
        u, err := url.Parse(src)
        if err != nil {
            return fmt.Errorf("bad docker host %q: %w", src, err)
        }
        if u.Hostname() == "" {
            return fmt.Errorf("docker host %q missing hostname", src)
        }
    }
    return nil
}

When it happens

Trigger: A docker widget source like 'tcp://host :2375' (space), 'tcp://[bad', or containing control characters; usually the result of a YAML typo or unquoted value that YAML mangles.

Common situations: Unquoted YAML scalar being interpreted oddly (e.g. 'tcp://host:2375' is usually fine, but values with colons/spaces need quotes); copy-paste artifacts; template variables producing empty host.

Related errors

• %s widget: %v
• recursion depth limit of %d reached
• no pages configured
• user has no name
• assets directory does not exist: %s

AI-assisted analysis of glanceapp/glance@91324e8de7 (2026-08-15). Data as JSON: /api/errors/1673245bcd61a741. Report an issue: GitHub.