func pickFirstVisibleNamespace(ps *PushContext, byNamespace map[string]*Service, configNamespace string) string {
	nss := make([]string, 0, len(byNamespace))
	for ns := range byNamespace {
		if ps.IsServiceVisible(byNamespace[ns], configNamespace) {
			nss = append(nss, ns)
		}
	}
	if len(nss) > 0 {
		sort.Strings(nss)
		return nss[0]
	}
	return ""

		s, exist := push.ServiceIndex.HostnameAndNamespace[hostname][virtualService.Namespace]
		if exist {
			// We should check whether the selected service is visible to the proxy node.
			if push.IsServiceVisible(s, node.ConfigNamespace) {
				service = s
			}
		}
		// If we find no service for the namespace of virtualService or the selected service is not visible to the proxy node,