Adding DisableBootstrapAfterElect config to disable bootstrap

config.go

@@ -32,6 +32,13 @@ type Config struct {
 	// we can become a leader of a cluster containing only this node.
 	ShutdownOnRemove bool
 
+	// DisableBootstrapAfterElect is used to turn off EnableSingleNode
+	// after the node is elected. This is used to prevent self-election
+	// if the node is removed from the Raft cluster via RemovePeer. Setting
+	// it to false will keep the bootstrap mode, allowing the node to self-elect
+	// and potentially bootstrap a seperate cluster.
+	DisableBootstrapAfterElect bool
+
 	// TrailingLogs controls how many logs we leave after a snapshot. This is
 	// used so that we can quickly replay logs on a follower instead of being
 	// forced to send an entire snapshot.
@@ -65,16 +72,17 @@ type Config struct {
 // DefaultConfig returns a Config with usable defaults.
 func DefaultConfig() *Config {
 	return &Config{
-		HeartbeatTimeout:   1000 * time.Millisecond,
-		ElectionTimeout:    1000 * time.Millisecond,
-		CommitTimeout:      50 * time.Millisecond,
-		MaxAppendEntries:   64,
-		ShutdownOnRemove:   true,
-		TrailingLogs:       10240,
-		SnapshotInterval:   120 * time.Second,
-		SnapshotThreshold:  8192,
-		EnableSingleNode:   false,
-		LeaderLeaseTimeout: 500 * time.Millisecond,
+		HeartbeatTimeout:           1000 * time.Millisecond,
+		ElectionTimeout:            1000 * time.Millisecond,
+		CommitTimeout:              50 * time.Millisecond,
+		MaxAppendEntries:           64,
+		ShutdownOnRemove:           true,
+		DisableBootstrapAfterElect: true,
+		TrailingLogs:               10240,
+		SnapshotInterval:           120 * time.Second,
+		SnapshotThreshold:          8192,
+		EnableSingleNode:           false,
+		LeaderLeaseTimeout:         500 * time.Millisecond,
 	}
 }
 

raft.go

@@ -751,6 +751,14 @@ func (r *Raft) runLeader() {
 	}
 	r.dispatchLogs([]*logFuture{noop})
 
+	// Disable EnableSingleNode after we've been elected leader.
+	// This is to prevent a split brain in the future, if we are removed
+	// from the cluster and then elect ourself as leader.
+	if r.conf.DisableBootstrapAfterElect && r.conf.EnableSingleNode {
+		r.logger.Printf("[INFO] raft: Disabling EnableSingleNode (bootstrap)")
+		r.conf.EnableSingleNode = false
+	}
+
 	// Sit in the leader loop until we step down
 	r.leaderLoop()
 }

raft_test.go

@@ -841,11 +841,61 @@ func TestRaft_RemoveLeader(t *testing.T) {
 	}
 }
 
+func TestRaft_RemoveLeader_NoShutdown(t *testing.T) {
+	// Make a cluster
+	conf := inmemConfig()
+	conf.ShutdownOnRemove = false
+	c := MakeCluster(3, t, conf)
+	defer c.Close()
+
+	// Get the leader
+	leader := c.Leader()
+
+	// Wait until we have 2 followers
+	limit := time.Now().Add(200 * time.Millisecond)
+	var followers []*Raft
+	for time.Now().Before(limit) && len(followers) != 2 {
+		time.Sleep(10 * time.Millisecond)
+		followers = c.GetInState(Follower)
+	}
+	if len(followers) != 2 {
+		t.Fatalf("expected two followers: %v", followers)
+	}
+
+	// Remove the leader
+	leader.RemovePeer(leader.localAddr)
+
+	// Wait a while
+	time.Sleep(20 * time.Millisecond)
+
+	// Should have a new leader
+	newLeader := c.Leader()
+
+	// Wait a bit for log application
+	time.Sleep(20 * time.Millisecond)
+
+	// Other nodes should have fewer peers
+	if peers, _ := newLeader.peerStore.Peers(); len(peers) != 2 {
+		t.Fatalf("too many peers")
+	}
+
+	// Old leader should be a follower
+	if leader.State() != Follower {
+		t.Fatalf("leader should be shutdown")
+	}
+
+	// Old leader should have no peers
+	if peers, _ := leader.peerStore.Peers(); len(peers) != 1 {
+		t.Fatalf("leader should have no peers")
+	}
+}
+
 func TestRaft_RemoveLeader_SplitCluster(t *testing.T) {
 	// Enable operation after a remove
 	conf := inmemConfig()
 	conf.EnableSingleNode = true
 	conf.ShutdownOnRemove = false
+	conf.DisableBootstrapAfterElect = false
 
 	// Make a cluster
 	c := MakeCluster(3, t, conf)