Rejoin join nodes automatically

This adds a --rejoin setting for rejoining
cluter nodes automatically when gone.

config.go

@@ -13,6 +13,7 @@ import (
 type config struct {
 	ClusterKey    []byte   `id:"cluster-key" desc:"shared key for cluster membership; must be 32 bytes base64 encoded; will be generated if not provided"`
 	Join          []string `desc:"comma separated list of hostnames or IP addresses to existing cluster members; if not provided, will attempt resuming any known state or otherwise wait for further members."`
+	Rejoin        int      `desc:"interval at which join nodes are joined again if away, 0 disables rejoining altogether" default:"0"`
 	Init          bool     `desc:"whether to explicitly (re)initialize the cluster; any known state from previous runs will be forgotten"`
 	BindAddr      string   `id:"bind-addr" desc:"IP address to bind to for cluster membership traffic (cannot be used with --bind-iface)"`
 	BindIface     string   `id:"bind-iface" desc:"Interface to bind to for cluster membership traffic (cannot be used with --bind-addr)"`

main.go

@@ -50,6 +50,12 @@ func main() {
 		Logger: logrus.StandardLogger(),
 	}
 
+	// Prepare the rejoin timer
+	rejoin := make(<-chan time.Time)
+	if config.Rejoin > 0 {
+		rejoin = time.Tick(time.Duration(1000000000 * config.Rejoin))
+	}
+
 	// Join the cluster
 	cluster.Update(localNode)
 	nodec := cluster.Members() // avoid deadlocks by starting before join
@@ -96,6 +102,9 @@ func main() {
 			logrus.Info("announcing new routes...")
 			localNode.Routes = routes
 			cluster.Update(localNode)
+		case <-rejoin:
+			logrus.Debug("rejoining missing join nodes...")
+			cluster.Join(config.Join)
 		case <-incomingSigs:
 			logrus.Info("terminating...")
 			cluster.Leave()