feat: support multiple DNS discovery URLs (#309)

waku.go

@@ -354,10 +354,10 @@ func main() {
 			Usage:       "Enable DNS discovery",
 			Destination: &options.DNSDiscovery.Enable,
 		},
-		&cli.StringFlag{
+		&cli.StringSliceFlag{
 			Name:        "dns-discovery-url",
 			Usage:       "URL for DNS node list in format 'enrtree://<key>@<fqdn>'",
-			Destination: &options.DNSDiscovery.URL,
+			Destination: &options.DNSDiscovery.URLs,
 		},
 		&cli.StringFlag{
 			Name:        "dns-discovery-name-server",

waku/node.go

@@ -226,18 +226,20 @@ func Execute(options Options) {
 
 	var discoveredNodes []dnsdisc.DiscoveredNode
 	if options.DNSDiscovery.Enable {
-		if options.DNSDiscovery.URL != "" {
-			logger.Info("attempting DNS discovery with ", zap.String("URL", options.DNSDiscovery.URL))
-			nodes, err := dnsdisc.RetrieveNodes(ctx, options.DNSDiscovery.URL, dnsdisc.WithNameserver(options.DNSDiscovery.Nameserver))
-			if err != nil {
-				logger.Warn("dns discovery error ", zap.Error(err))
-			} else {
-				var discAddresses []multiaddr.Multiaddr
-				for _, n := range nodes {
-					discAddresses = append(discAddresses, n.Addresses...)
+		if len(options.DNSDiscovery.URLs.Value()) != 0 {
+			for _, url := range options.DNSDiscovery.URLs.Value() {
+				logger.Info("attempting DNS discovery with ", zap.String("URL", url))
+				nodes, err := dnsdisc.RetrieveNodes(ctx, url, dnsdisc.WithNameserver(options.DNSDiscovery.Nameserver))
+				if err != nil {
+					logger.Warn("dns discovery error ", zap.Error(err))
+				} else {
+					var discAddresses []multiaddr.Multiaddr
+					for _, n := range nodes {
+						discAddresses = append(discAddresses, n.Addresses...)
+					}
+					logger.Info("found dns entries ", logging.MultiAddrs("nodes", discAddresses...))
+					discoveredNodes = nodes
 				}
-				logger.Info("found dns entries ", logging.MultiAddrs("nodes", discAddresses...))
-				discoveredNodes = nodes
 			}
 		} else {
 			logger.Fatal("DNS discovery URL is required")

waku/options.go

@@ -103,7 +103,7 @@ type SwapOptions struct {
 // information for nodes. It's very useful for bootstrapping a p2p network.
 type DNSDiscoveryOptions struct {
 	Enable     bool
-	URL        string
+	URLs       cli.StringSlice
 	Nameserver string
 }