grpc/grpc-go · error

method name must be non empty

Error message

method name must be non empty

What it means

Returned by validateMethodString when the method part (the segment after the '/') is empty. The function splits by '/' and checks serviceMethod[1] == "". This catches patterns like pkg.Service/ where the service is specified but no method name follows the slash.

Solutions

1. Provide a concrete method name (foo.Bar/Method) or use the wildcard (foo.Bar/*) to match all methods.
2. Fix config-generation templates that append a trailing slash without a method suffix.

Example fix

// before
{"methods":["foo.Bar/"]} // trailing slash, empty method
// after
{"methods":["foo.Bar/*"]} // match all methods in service

parts := strings.Split(method, "/")
if len(parts) == 2 && parts[1] == "" {
    return fmt.Errorf("method name after / must be non-empty; use * for wildcard")
}

func isValidMethodPattern(m string) bool {
    parts := strings.Split(m, "/")
    return len(parts) == 2 && parts[1] != ""
}

When it happens

Trigger: A method entry in the observability config ends with a trailing slash and no method name, e.g., foo.Bar/. The split produces ["foo.Bar", ""], and the empty second element triggers the error.

Common situations: Developers use a trailing slash intending it as a prefix or directory separator (common in REST-style path thinking), or accidentally leave it after editing. Also from templated config generation that appends '/' unconditionally.

Related errors

• cannot have a leading slash
• cannot have exclude and a '*' wildcard
• / must come in between service and method, only one /
• empty string is not a valid method binary logging config
• grpc: the provided default service config is invalid

AI-assisted analysis of grpc/grpc-go@0c51461d27 (2026-08-11). Data as JSON: /api/errors/1b80011d4ac27983. Report an issue: GitHub.

Appendix: source

Thrown at gcp/observability/config.go:68

		logger.Infof("Failed to find project ID in default credential: %v", err)
		return ""
	}
	logger.Infof("Found project ID from Google Default Credential: %v", credentials.ProjectID)
	return credentials.ProjectID
}

// validateMethodString validates whether the string passed in is a valid
// pattern.
func validateMethodString(method string) error {
	if strings.HasPrefix(method, "/") {
		return errors.New("cannot have a leading slash")
	}
	serviceMethod := strings.Split(method, "/")
	if len(serviceMethod) != 2 {
		return errors.New("/ must come in between service and method, only one /")
	}
	if serviceMethod[1] == "" {
		return errors.New("method name must be non empty")
	}
	if serviceMethod[0] == "*" {
		return errors.New("cannot have service wildcard * i.e. (*/m)")
	}
	return nil
}

func validateLogEventMethod(methods []string, exclude bool) error {
	for _, method := range methods {
		if method == "*" {
			if exclude {
				return errors.New("cannot have exclude and a '*' wildcard")
			}
			continue
		}
		if err := validateMethodString(method); err != nil {
			return fmt.Errorf("invalid method string: %v, err: %v", method, err)
		}

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