func NewDiscovery(conf SDConfig, logger log.Logger) *Discovery {
	if logger == nil {
		logger = log.NewNopLogger()
	}

	qtype := dns.TypeSRV
	switch strings.ToUpper(conf.Type) {
	case "A":
		qtype = dns.TypeA
	case "AAAA":
		qtype = dns.TypeAAAA
	case "SRV":
		qtype = dns.TypeSRV
	}
	d := &Discovery{
		names:    conf.Names,
		qtype:    qtype,
		port:     conf.Port,
		logger:   logger,
		lookupFn: lookupWithSearchPath,
	}
	d.Discovery = refresh.NewDiscovery(
		logger,
		"dns",
		time.Duration(conf.RefreshInterval),
		d.refresh,
	)
	return d
}
func NewDiscovery(conf SDConfig, logger log.Logger) *Discovery {
	if logger == nil {
		logger = log.NewNopLogger()
	}

	qtype := dns.TypeSRV
	switch strings.ToUpper(conf.Type) {
	case "A":
		qtype = dns.TypeA
	case "AAAA":
		qtype = dns.TypeAAAA
	case "SRV":
		qtype = dns.TypeSRV
	}
	d := &Discovery{
		names:    conf.Names,
		qtype:    qtype,
		port:     conf.Port,
		logger:   logger,
		lookupFn: lookupWithSearchPath,
	}
	d.Discovery = refresh.NewDiscovery(
		logger,
		"dns",
		time.Duration(conf.RefreshInterval),
		d.refresh,
	)
	return d
}
// NewDiscovery returns a new Discovery which periodically refreshes its targets.