rafthttp: add AddRemote

Add remotes to rafthttp, who help newly joined members catch up the
progress of the cluster. It supports basic message sending to remote, and
has no stream connection for simplicity. remotes will not be used
after the latest peers have been added into rafthttp.

etcdserver/server.go

@@ -168,6 +168,7 @@ func NewServer(cfg *ServerConfig) (*EtcdServer, error) {
 	haveWAL := wal.Exist(cfg.WALDir())
 	ss := snap.New(cfg.SnapDir())
 
+	var remotes []*Member
 	switch {
 	case !haveWAL && !cfg.NewCluster:
 		if err := cfg.VerifyJoinExisting(); err != nil {
@@ -180,6 +181,7 @@ func NewServer(cfg *ServerConfig) (*EtcdServer, error) {
 		if err := ValidateClusterAndAssignIDs(cfg.Cluster, existingCluster); err != nil {
 			return nil, fmt.Errorf("error validating peerURLs %s: %v", existingCluster, err)
 		}
+		remotes = existingCluster.Members()
 		cfg.Cluster.SetID(existingCluster.id)
 		cfg.Cluster.SetStore(st)
 		cfg.Print()
@@ -269,8 +271,14 @@ func NewServer(cfg *ServerConfig) (*EtcdServer, error) {
 		reqIDGen:   idutil.NewGenerator(uint8(id), time.Now()),
 	}
 
+	// TODO: move transport initialization near the definition of remote
 	tr := rafthttp.NewTransporter(cfg.Transport, id, cfg.Cluster.ID(), srv, srv.errorc, sstats, lstats)
-	// add all the remote members into sendhub
+	// add all remotes into transport
+	for _, m := range remotes {
+		if m.ID != id {
+			tr.AddRemote(m.ID, m.PeerURLs)
+		}
+	}
 	for _, m := range cfg.Cluster.Members() {
 		if m.ID != id {
 			tr.AddPeer(m.ID, m.PeerURLs)

etcdserver/server_test.go

@@ -1366,6 +1366,7 @@ type nopTransporter struct{}
 
 func (s *nopTransporter) Handler() http.Handler               { return nil }
 func (s *nopTransporter) Send(m []raftpb.Message)             {}
+func (s *nopTransporter) AddRemote(id types.ID, us []string)  {}
 func (s *nopTransporter) AddPeer(id types.ID, us []string)    {}
 func (s *nopTransporter) RemovePeer(id types.ID)              {}
 func (s *nopTransporter) RemoveAllPeers()                     {}

rafthttp/pipeline.go

@@ -101,7 +101,7 @@ func (p *pipeline) handle() {
 				log.Printf("pipeline: the connection with %s became inactive", p.id)
 				p.active = false
 			}
-			if m.Type == raftpb.MsgApp {
+			if m.Type == raftpb.MsgApp && p.fs != nil {
 				p.fs.Fail()
 			}
 			p.r.ReportUnreachable(m.To)
@@ -114,7 +114,7 @@ func (p *pipeline) handle() {
 				p.active = true
 				p.errored = nil
 			}
-			if m.Type == raftpb.MsgApp {
+			if m.Type == raftpb.MsgApp && p.fs != nil {
 				p.fs.Succ(end.Sub(start))
 			}
 			if isMsgSnap(m) {

rafthttp/remote.go

@@ -0,0 +1,48 @@
+// Copyright 2015 CoreOS, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package rafthttp
+
+import (
+	"log"
+	"net/http"
+
+	"github.com/coreos/etcd/pkg/types"
+	"github.com/coreos/etcd/raft/raftpb"
+)
+
+type remote struct {
+	id       types.ID
+	pipeline *pipeline
+}
+
+func startRemote(tr http.RoundTripper, urls types.URLs, local, to, cid types.ID, r Raft, errorc chan error) *remote {
+	picker := newURLPicker(urls)
+	return &remote{
+		id:       to,
+		pipeline: newPipeline(tr, picker, to, cid, nil, r, errorc),
+	}
+}
+
+func (g *remote) Send(m raftpb.Message) {
+	select {
+	case g.pipeline.msgc <- m:
+	default:
+		log.Printf("remote: dropping %s to %s since pipeline with %d-size buffer is blocked", m.Type, g.id, pipelineBufSize)
+	}
+}
+
+func (g *remote) Stop() {
+	g.pipeline.stop()
+}

rafthttp/transport.go

@@ -45,6 +45,12 @@ type Transporter interface {
 	// If the id cannot be found in the transport, the message
 	// will be ignored.
 	Send(m []raftpb.Message)
+	// AddRemote adds a remote with given peer urls into the transport.
+	// A remote helps newly joined member to catch up the progress of cluster,
+	// and will not be used after that.
+	// It is the caller's responsibility to ensure the urls are all vaild,
+	// or it panics.
+	AddRemote(id types.ID, urls []string)
 	// AddPeer adds a peer with given peer urls into the transport.
 	// It is the caller's responsibility to ensure the urls are all vaild,
 	// or it panics.
@@ -70,9 +76,10 @@ type transport struct {
 	serverStats  *stats.ServerStats
 	leaderStats  *stats.LeaderStats
 
-	mu     sync.RWMutex      // protect the peer map
-	peers  map[types.ID]Peer // remote peers
-	errorc chan error
+	mu      sync.RWMutex         // protect the remote and peer map
+	remotes map[types.ID]*remote // remotes map that helps newly joined member to catch up
+	peers   map[types.ID]Peer    // peers map
+	errorc  chan error
 }
 
 func NewTransporter(rt http.RoundTripper, id, cid types.ID, r Raft, errorc chan error, ss *stats.ServerStats, ls *stats.LeaderStats) Transporter {
@@ -83,6 +90,7 @@ func NewTransporter(rt http.RoundTripper, id, cid types.ID, r Raft, errorc chan
 		raft:         r,
 		serverStats:  ss,
 		leaderStats:  ls,
+		remotes:      make(map[types.ID]*remote),
 		peers:        make(map[types.ID]Peer),
 		errorc:       errorc,
 	}
@@ -110,21 +118,30 @@ func (t *transport) Send(msgs []raftpb.Message) {
 			continue
 		}
 		to := types.ID(m.To)
+
 		p, ok := t.peers[to]
-		if !ok {
-			log.Printf("etcdserver: send message to unknown receiver %s", to)
+		if ok {
+			if m.Type == raftpb.MsgApp {
+				t.serverStats.SendAppendReq(m.Size())
+			}
+			p.Send(m)
 			continue
 		}
 
-		if m.Type == raftpb.MsgApp {
-			t.serverStats.SendAppendReq(m.Size())
+		g, ok := t.remotes[to]
+		if ok {
+			g.Send(m)
+			continue
 		}
 
-		p.Send(m)
+		log.Printf("etcdserver: send message to unknown receiver %s", to)
 	}
 }
 
 func (t *transport) Stop() {
+	for _, r := range t.remotes {
+		r.Stop()
+	}
 	for _, p := range t.peers {
 		p.Stop()
 	}
@@ -133,6 +150,19 @@ func (t *transport) Stop() {
 	}
 }
 
+func (t *transport) AddRemote(id types.ID, us []string) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	if _, ok := t.remotes[id]; ok {
+		return
+	}
+	urls, err := types.NewURLs(us)
+	if err != nil {
+		log.Panicf("newURLs %+v should never fail: %+v", us, err)
+	}
+	t.remotes[id] = startRemote(t.roundTripper, urls, t.id, id, t.clusterID, t.raft, t.errorc)
+}
+
 func (t *transport) AddPeer(id types.ID, us []string) {
 	t.mu.Lock()
 	defer t.mu.Unlock()