Assign and store a node ID when joining an existing cluster

meta/internal/meta.pb.go

@@ -1256,10 +1256,13 @@ func (m *JoinRequest) GetAddr() string {
 
 type JoinResponse struct {
 	Header *ResponseHeader `protobuf:"bytes,1,req" json:"Header,omitempty"`
+	// Indicates that this node should take part in the raft cluster.
 	EnableRaft *bool `protobuf:"varint,2,opt" json:"EnableRaft,omitempty"`
 	// The addresses of raft peers to use if joining as a raft member. If not joining
 	// as a raft member, these are the nodes running raft.
 	Peers []string `protobuf:"bytes,3,rep" json:"Peers,omitempty"`
+	// The node ID assigned to the requesting node.
+	NodeID           *uint64 `protobuf:"varint,4,opt" json:"NodeID,omitempty"`
 	XXX_unrecognized []byte  `json:"-"`
 }
 
@@ -1288,6 +1291,13 @@ func (m *JoinResponse) GetPeers() []string {
 	return nil
 }
 
+func (m *JoinResponse) GetNodeID() uint64 {
+	if m != nil && m.NodeID != nil {
+		return *m.NodeID
+	}
+	return 0
+}
+
 func init() {
 	proto.RegisterEnum("internal.RPCType", RPCType_name, RPCType_value)
 	proto.RegisterEnum("internal.Command_Type", Command_Type_name, Command_Type_value)

meta/internal/meta.proto

@@ -290,8 +290,12 @@ message JoinResponse {
     required ResponseHeader Header = 1;
 
 
+    // Indicates that this node should take part in the raft cluster.
     optional bool EnableRaft = 2;
     // The addresses of raft peers to use if joining as a raft member. If not joining
     // as a raft member, these are the nodes running raft.
     repeated string Peers = 3;
+
+    // The node ID assigned to the requesting node.
+    optional uint64 NodeID = 4;
 }

meta/rpc.go

@@ -23,12 +23,15 @@ type RPC struct {
 		Leader() string
 		Peers() []string
 		AddPeer(host string) error
+		CreateNode(host string) (*NodeInfo, error)
+		NodeByHost(host string) (*NodeInfo, error)
 	}
 }
 
 type JoinResult struct {
 	RaftEnabled bool
 	Peers       []string
+	NodeID      uint64
 }
 
 type Reply interface {
@@ -138,17 +141,44 @@ func (r *RPC) handleFetchData() (*internal.FetchDataResponse, error) {
 
 // handleJoinRequest handles a request to join the cluster
 func (r *RPC) handleJoinRequest(req *internal.JoinRequest) (*internal.JoinResponse, error) {
-	if err := r.store.AddPeer(*req.Addr); err != nil {
-		r.Logger.Printf("join request failed: %v", err)
+
+	node, err := func() (*NodeInfo, error) {
+		// attempt to create the node
+		node, err := r.store.CreateNode(*req.Addr)
+		// if it exists, return the exting node
+		if err == ErrNodeExists {
+			return r.store.NodeByHost(*req.Addr)
+		} else if err != nil {
+			return nil, fmt.Errorf("create node: %v", err)
 		}
+
+		// If we have less than 3 nodes, add them as raft peers
+		if len(r.store.Peers()) < MaxRaftNodes {
+			if err = r.store.AddPeer(*req.Addr); err != nil {
+				return node, fmt.Errorf("add peer: %v", err)
+			}
+		}
+		return node, err
+	}()
+
+	nodeID := uint64(0)
+	if node != nil {
+		nodeID = node.ID
+	}
+
+	if err != nil {
+		r.Logger.Printf("join request failed: create node: %v", err)
+	}
+
 	r.Logger.Printf("recv join request from: %v", *req.Addr)
 	return &internal.JoinResponse{
 		Header: &internal.ResponseHeader{
 			OK: proto.Bool(true),
 		},
-		EnableRaft: proto.Bool(false),
+		EnableRaft: proto.Bool(contains(r.store.Peers(), *req.Addr)),
 		Peers:      r.store.Peers(),
-	}, nil
+		NodeID:     proto.Uint64(nodeID),
+	}, err
 
 }
 
@@ -219,6 +249,7 @@ func (r *RPC) join(localAddr, remoteAddr string) (*JoinResult, error) {
 	return &JoinResult{
 		RaftEnabled: resp.GetEnableRaft(),
 		Peers:       resp.GetPeers(),
+		NodeID:      resp.GetNodeID(),
 	}, nil
 
 }
@@ -267,3 +298,12 @@ func u64tob(v uint64) []byte {
 func btou64(b []byte) uint64 {
 	return binary.BigEndian.Uint64(b)
 }
+
+func contains(s []string, e string) bool {
+	for _, a := range s {
+		if a == e {
+			return true
+		}
+	}
+	return false
+}

meta/store.go

@@ -54,6 +54,7 @@ const (
 	raftSnapshotsRetained = 2
 	raftTransportMaxPool  = 3
 	raftTransportTimeout  = 10 * time.Second
+	MaxRaftNodes          = 3
 )
 
 // Store represents a raft-backed metastore.
@@ -326,6 +327,12 @@ func (s *Store) Open() error {
 		s.Logger.Printf("Joined remote node %v", s.join)
 		s.Logger.Printf("raftEnabled=%v peers=%v", res.RaftEnabled, res.Peers)
 		s.peers = res.Peers
+		s.id = res.NodeID
+
+		if err := s.writeNodeID(res.NodeID); err != nil {
+			return err
+		}
+
 		if !res.RaftEnabled {
 			s.raftState = &remoteRaft{s}
 			if err := s.invalidate(); err != nil {
@@ -336,7 +343,7 @@ func (s *Store) Open() error {
 
 	// Verify that no more than 3 peers.
 	// https://github.com/influxdb/influxdb/issues/2750
-	if len(s.peers) > 3 {
+	if len(s.peers) > MaxRaftNodes {
 		return ErrTooManyPeers
 	}
 
@@ -360,7 +367,7 @@ func (s *Store) Open() error {
 		s.opened = true
 
 		// Create the root directory if it doesn't already exist.
-		if err := os.MkdirAll(s.path, 0777); err != nil {
+		if err := s.createRootDir(); err != nil {
 			return fmt.Errorf("mkdir all: %s", err)
 		}
 
@@ -497,7 +504,7 @@ func (s *Store) createLocalNode() error {
 	}
 
 	// Write node id to file.
-	if err := ioutil.WriteFile(s.IDPath(), []byte(strconv.FormatUint(ni.ID, 10)), 0666); err != nil {
+	if err := s.writeNodeID(ni.ID); err != nil {
 		return fmt.Errorf("write file: %s", err)
 	}
 
@@ -509,6 +516,17 @@ func (s *Store) createLocalNode() error {
 	return nil
 }
 
+func (s *Store) createRootDir() error {
+	return os.MkdirAll(s.path, 0777)
+}
+
+func (s *Store) writeNodeID(id uint64) error {
+	if err := s.createRootDir(); err != nil {
+		return err
+	}
+	return ioutil.WriteFile(s.IDPath(), []byte(strconv.FormatUint(id, 10)), 0666)
+}
+
 // Snapshot saves a snapshot of the current state.
 func (s *Store) Snapshot() error {
 	future := s.raft.Snapshot()