Add support for DNS SRV -based discovery

cmd/rqlited/flags.go

@@ -19,6 +19,7 @@ const (
 	DiscoModeConsulKV = "consul-kv"
 	DiscoModeEtcdKV   = "etcd-kv"
 	DiscoModeDNS      = "dns"
+	DiscoModeDNSSRV   = "dns-srv"
 )
 
 // Config represents the configuration as set by command-line flags.
@@ -243,7 +244,7 @@ func (c *Config) Validate() error {
 		if c.BootstrapExpect > 0 {
 			return fmt.Errorf("bootstrapping not applicable when using %s", c.DiscoMode)
 		}
-	case DiscoModeDNS:
+	case DiscoModeDNS, DiscoModeDNSSRV:
 		if c.BootstrapExpect == 0 {
 			return fmt.Errorf("bootstrap-expect value required when using %s", c.DiscoMode)
 		}

cmd/rqlited/main.go

@@ -18,6 +18,7 @@ import (
 
 	consul "github.com/rqlite/rqlite-disco-clients/consul"
 	"github.com/rqlite/rqlite-disco-clients/dns"
+	"github.com/rqlite/rqlite-disco-clients/dnssrv"
 	etcd "github.com/rqlite/rqlite-disco-clients/etcd"
 	"github.com/rqlite/rqlite/auth"
 	"github.com/rqlite/rqlite/cluster"
@@ -370,8 +371,8 @@ func createCluster(cfg *Config, tlsConfig *tls.Config, hasPeers bool, str *store
 	}
 	log.Printf("discovery mode: %s", cfg.DiscoMode)
 
-	// DNS disco is special.
-	if cfg.DiscoMode == DiscoModeDNS {
+	// DNS-based discovery involves a few different options.
+	if cfg.DiscoMode == DiscoModeDNS || cfg.DiscoMode == DiscoModeDNSSRV {
 		if hasPeers {
 			log.Printf("preexisting node configuration detected, ignoring %s", cfg.DiscoMode)
 			return nil
@@ -382,19 +383,33 @@ func createCluster(cfg *Config, tlsConfig *tls.Config, hasPeers bool, str *store
 				rc.Close()
 			}
 		}()
-		dnsCfg, err := dns.NewConfigFromReader(rc)
-		if err != nil {
-			return fmt.Errorf("error reading DNS configuration: %s", err.Error())
+
+		var provider interface {
+			cluster.AddressProvider
+			httpd.StatusReporter
+		}
+		if cfg.DiscoMode == DiscoModeDNS {
+			dnsCfg, err := dns.NewConfigFromReader(rc)
+			if err != nil {
+				return fmt.Errorf("error reading DNS configuration: %s", err.Error())
+			}
+			provider = dns.New(dnsCfg)
+
+		} else {
+			dnssrvCfg, err := dnssrv.NewConfigFromReader(rc)
+			if err != nil {
+				return fmt.Errorf("error reading DNS configuration: %s", err.Error())
+			}
+			provider = dnssrv.New(dnssrvCfg)
 		}
-		dnsClient := dns.New(dnsCfg)
 
-		bs := cluster.NewBootstrapper(dnsClient, cfg.BootstrapExpect, tlsConfig)
+		bs := cluster.NewBootstrapper(provider, cfg.BootstrapExpect, tlsConfig)
 		done := func() bool {
 			leader, _ := str.LeaderAddr()
 			return leader != ""
 		}
+		httpServ.RegisterStatus("disco", provider)
 
-		httpServ.RegisterStatus("disco", dnsClient)
 		return bs.Boot(str.ID(), cfg.RaftAdv, done, cfg.BootstrapExpectTimeout)
 	} else {
 		discoService, err := createDiscoService(cfg, str)

go.mod

@@ -21,7 +21,7 @@ require (
 	github.com/mkideal/pkg v0.1.3
 	github.com/rqlite/go-sqlite3 v1.22.0
 	github.com/rqlite/raft-boltdb v0.0.0-20211018013422-771de01086ce
-	github.com/rqlite/rqlite-disco-clients v0.0.0-20220130234129-c05d8e6f4a92
+	github.com/rqlite/rqlite-disco-clients v0.0.0-20220131053835-8891a23a4eed
 	go.etcd.io/bbolt v1.3.6
 	go.uber.org/atomic v1.9.0 // indirect
 	go.uber.org/multierr v1.7.0 // indirect

go.sum

@@ -251,8 +251,8 @@ github.com/rqlite/go-sqlite3 v1.22.0 h1:twqvKzylJXG62Qe0rcqdy5ClGhc0YRc2vvA3nEXw
 github.com/rqlite/go-sqlite3 v1.22.0/go.mod h1:ml55MVv28UP7V8zrxILd2EsrI6Wfsz76YSskpg08Ut4=
 github.com/rqlite/raft-boltdb v0.0.0-20211018013422-771de01086ce h1:sVlzmCJiaM0LGK3blAHOD/43QxJZ8bLCDcsqZRatnFE=
 github.com/rqlite/raft-boltdb v0.0.0-20211018013422-771de01086ce/go.mod h1:mc+WNDHyskdViYAoPnaMXEBnSKBmoUgiEZjrlAj6G34=
-github.com/rqlite/rqlite-disco-clients v0.0.0-20220130234129-c05d8e6f4a92 h1:Pfq4lSuNANFRRQDODU2Rcy+rJH7ezDKJiM6rKqDpBAk=
-github.com/rqlite/rqlite-disco-clients v0.0.0-20220130234129-c05d8e6f4a92/go.mod h1:pym85nj6JnCI7rM9RxTZ4cubkTQyyg7uLwVydso9B80=
+github.com/rqlite/rqlite-disco-clients v0.0.0-20220131053835-8891a23a4eed h1:Rr6Ubr916vDhZR5+2ZTsuno0Of285BQEskkorWMZZLU=
+github.com/rqlite/rqlite-disco-clients v0.0.0-20220131053835-8891a23a4eed/go.mod h1:pym85nj6JnCI7rM9RxTZ4cubkTQyyg7uLwVydso9B80=
 github.com/ryanuber/columnize v0.0.0-20160712163229-9b3edd62028f/go.mod h1:sm1tb6uqfes/u+d4ooFouqFdy9/2g9QGwK3SQygK0Ts=
 github.com/sean-/seed v0.0.0-20170313163322-e2103e2c3529 h1:nn5Wsu0esKSJiIVhscUtVbo7ada43DJhG55ua/hjS5I=
 github.com/sean-/seed v0.0.0-20170313163322-e2103e2c3529/go.mod h1:DxrIzT+xaE7yg65j358z/aeFdxmN0P9QXhEzd20vsDc=