micro/go-micro · error

missing service instance name

Error message

missing service instance name

What it means

NewMDNSService requires a non-empty instance name — the human-readable service instance label advertised on the network (e.g. "My Printer"). An empty string fails the initial sanity checks and returns this error before any network setup.

Solutions

1. Pass a non-empty instance name, e.g. NewMDNSService("My App", "_http._tcp", "", "", port, ips, txt)
2. Validate config/environment before registration and substitute a default name if empty
3. In Register(), ensure the caller-provided instance is populated before constructing the service

Example fix

// before
svc, err := NewMDNSService(instance, "_http._tcp", "", "", 8080, ips, nil) // instance == ""
// after
if instance == "" {
	instance = filepath.Base(os.Args[0])
}
svc, err := NewMDNSService(instance, "_http._tcp", "", "", 8080, ips, nil)

if strings.TrimSpace(instance) == "" {
	instance = filepath.Base(os.Args[0])
}
// safe to call NewMDNSService(instance, ...)

func hasInstanceName(s string) bool { return strings.TrimSpace(s) != "" }

svc, err := NewMDNSService(instance, service, domain, hostName, port, ips, txt)
if err != nil {
	if strings.Contains(err.Error(), "missing service instance name") {
		return fmt.Errorf("service display name is required in configuration: %w", err)
	}
	return err
}

When it happens

Trigger: Calling NewMDNSService("", service, domain, hostName, port, ips, txt) — an empty instance argument, often from an unset config field or empty derived value.

Common situations: Registering a service where the display name comes from an app config or environment variable that is unset; a generated name builder returning "" on failure.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• missing service name
• missing service port
• addr (nats subject) must not be empty
• ai model is nil
• domain is not a fully-qualified domain name

AI-assisted analysis of micro/go-micro@24529f1404 (2026-09-01). Data as JSON: /api/errors/82abde45849c45f0. Report an issue: GitHub.

Appendix: source

Thrown at internal/util/mdns/zone.go:67

	// TODO(reddaly): Perform full validation.

	return nil
}

// NewMDNSService returns a new instance of MDNSService.
//
// If domain, hostName, or ips is set to the zero value, then a default value
// will be inferred from the operating system.
//
// TODO(reddaly): This interface may need to change to account for "unique
// record" conflict rules of the mDNS protocol.  Upon startup, the server should
// check to ensure that the instance name does not conflict with other instance
// names, and, if required, select a new name.  There may also be conflicting
// hostName A/AAAA records.
func NewMDNSService(instance, service, domain, hostName string, port int, ips []net.IP, txt []string) (*MDNSService, error) {
	// Sanity check inputs
	if instance == "" {
		return nil, fmt.Errorf("missing service instance name")
	}
	if service == "" {
		return nil, fmt.Errorf("missing service name")
	}
	if port == 0 {
		return nil, fmt.Errorf("missing service port")
	}

	// Set default domain
	if domain == "" {
		domain = "local."
	}
	if err := validateFQDN(domain); err != nil {
		return nil, fmt.Errorf("domain %q is not a fully-qualified domain name: %v", domain, err)
	}

	// Get host information if no host is specified.
	if hostName == "" {

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