// 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 etcdserver
import (
"encoding/json"
"expvar"
"os"
"sort"
"sync"
"sync/atomic"
"time"
"github.com/coreos/etcd/Godeps/_workspace/src/github.com/coreos/pkg/capnslog"
pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
"github.com/coreos/etcd/pkg/pbutil"
"github.com/coreos/etcd/pkg/types"
"github.com/coreos/etcd/raft"
"github.com/coreos/etcd/raft/raftpb"
"github.com/coreos/etcd/rafthttp"
"github.com/coreos/etcd/wal"
"github.com/coreos/etcd/wal/walpb"
)
const (
// Number of entries for slow follower to catch-up after compacting
// the raft storage entries.
// We expect the follower has a millisecond level latency with the leader.
// The max throughput is around 10K. Keep a 5K entries is enough for helping
// follower to catch up.
numberOfCatchUpEntries = 5000
// The max throughput of etcd will not exceed 100MB/s (100K * 1KB value).
// Assuming the RTT is around 10ms, 1MB max size is large enough.
maxSizePerMsg = 1 * 1024 * 1024
// Never overflow the rafthttp buffer, which is 4096.
// TODO: a better const?
maxInflightMsgs = 4096 / 8
)
var (
// protects raftStatus
raftStatusMu sync.Mutex
// indirection for expvar func interface
// expvar panics when publishing duplicate name
// expvar does not support remove a registered name
// so only register a func that calls raftStatus
// and change raftStatus as we need.
raftStatus func() raft.Status
)
func init() {
raft.SetLogger(capnslog.NewPackageLogger("github.com/coreos/etcd", "raft"))
expvar.Publish("raft.status", expvar.Func(func() interface{} {
raftStatusMu.Lock()
defer raftStatusMu.Unlock()
return raftStatus()
}))
}
type RaftTimer interface {
Index() uint64
Term() uint64
}
// apply contains entries, snapshot to be applied. Once
// an apply is consumed, the entries will be persisted to
// to raft storage concurrently; the application must read
// raftDone before assuming the raft messages are stable.
type apply struct {
entries []raftpb.Entry
snapshot raftpb.Snapshot
raftDone <-chan struct{} // rx {} after raft has persisted messages
}
type raftNode struct {
// Cache of the latest raft index and raft term the server has seen.
// These three unit64 fields must be the first elements to keep 64-bit
// alignment for atomic access to the fields.
index uint64
term uint64
lead uint64
mu sync.Mutex
// last lead elected time
lt time.Time
raft.Node
// a chan to send out apply
applyc chan apply
// TODO: remove the etcdserver related logic from raftNode
// TODO: add a state machine interface to apply the commit entries
// and do snapshot/recover
s *EtcdServer
// utility
ticker <-chan time.Time
raftStorage *raft.MemoryStorage
storage Storage
// transport specifies the transport to send and receive msgs to members.
// Sending messages MUST NOT block. It is okay to drop messages, since
// clients should timeout and reissue their messages.
// If transport is nil, server will panic.
transport rafthttp.Transporter
stopped chan struct{}
done chan struct{}
}
// start prepares and starts raftNode in a new goroutine. It is no longer safe
// to modify the fields after it has been started.
// TODO: Ideally raftNode should get rid of the passed in server structure.
func (r *raftNode) start(s *EtcdServer) {
r.s = s
r.applyc = make(chan apply)
r.stopped = make(chan struct{})
r.done = make(chan struct{})
go func() {
var syncC <-chan time.Time
defer r.onStop()
for {
select {
case <-r.ticker:
r.Tick()
case rd := <-r.Ready():
if rd.SoftState != nil {
if lead := atomic.LoadUint64(&r.lead); rd.SoftState.Lead != raft.None && lead != rd.SoftState.Lead {
r.mu.Lock()
r.lt = time.Now()
r.mu.Unlock()
}
atomic.StoreUint64(&r.lead, rd.SoftState.Lead)
if rd.RaftState == raft.StateLeader {
// TODO: raft should send server a notification through chan when
// it promotes or demotes instead of modifying server directly.
syncC = r.s.SyncTicker
if r.s.lessor != nil {
r.s.lessor.Promote()
}
// TODO: remove the nil checking
// current test utility does not provide the stats
if r.s.stats != nil {
r.s.stats.BecomeLeader()
}
} else {
if r.s.lessor != nil {
r.s.lessor.Demote()
}
syncC = nil
}
}
raftDone := make(chan struct{}, 1)
ap := apply{
entries: rd.CommittedEntries,
snapshot: rd.Snapshot,
raftDone: raftDone,
}
select {
case r.applyc <- ap:
case <-r.stopped:
return
}
if !raft.IsEmptySnap(rd.Snapshot) {
if err := r.storage.SaveSnap(rd.Snapshot); err != nil {
plog.Fatalf("raft save snapshot error: %v", err)
}
r.raftStorage.ApplySnapshot(rd.Snapshot)
plog.Infof("raft applied incoming snapshot at index %d", rd.Snapshot.Metadata.Index)
}
if err := r.storage.Save(rd.HardState, rd.Entries); err != nil {
plog.Fatalf("raft save state and entries error: %v", err)
}
r.raftStorage.Append(rd.Entries)
r.s.send(rd.Messages)
raftDone <- struct{}{}
r.Advance()
case <-syncC:
r.s.sync(r.s.cfg.ReqTimeout())
case <-r.stopped:
return
}
}
}()
}
func (r *raftNode) apply() chan apply {
return r.applyc
}
func (r *raftNode) leadElectedTime() time.Time {
r.mu.Lock()
defer r.mu.Unlock()
return r.lt
}
func (r *raftNode) stop() {
r.stopped <- struct{}{}
<-r.done
}
func (r *raftNode) onStop() {
r.Stop()
r.transport.Stop()
if err := r.storage.Close(); err != nil {
plog.Panicf("raft close storage error: %v", err)
}
close(r.done)
}
// for testing
func (r *raftNode) pauseSending() {
p := r.transport.(rafthttp.Pausable)
p.Pause()
}
func (r *raftNode) resumeSending() {
p := r.transport.(rafthttp.Pausable)
p.Resume()
}
// advanceTicksForElection advances ticks to the node for fast election.
// This reduces the time to wait for first leader election if bootstrapping the whole
// cluster, while leaving at least 1 heartbeat for possible existing leader
// to contact it.
func advanceTicksForElection(n raft.Node, electionTicks int) {
for i := 0; i < electionTicks-1; i++ {
n.Tick()
}
}
func startNode(cfg *ServerConfig, cl *cluster, ids []types.ID) (id types.ID, n raft.Node, s *raft.MemoryStorage, w *wal.WAL) {
var err error
member := cl.MemberByName(cfg.Name)
metadata := pbutil.MustMarshal(
&pb.Metadata{
NodeID: uint64(member.ID),
ClusterID: uint64(cl.ID()),
},
)
if err = os.MkdirAll(cfg.SnapDir(), privateDirMode); err != nil {
plog.Fatalf("create snapshot directory error: %v", err)
}
if w, err = wal.Create(cfg.WALDir(), metadata); err != nil {
plog.Fatalf("create wal error: %v", err)
}
peers := make([]raft.Peer, len(ids))
for i, id := range ids {
ctx, err := json.Marshal((*cl).Member(id))
if err != nil {
plog.Panicf("marshal member should never fail: %v", err)
}
peers[i] = raft.Peer{ID: uint64(id), Context: ctx}
}
id = member.ID
plog.Infof("starting member %s in cluster %s", id, cl.ID())
s = raft.NewMemoryStorage()
c := &raft.Config{
ID: uint64(id),
ElectionTick: cfg.ElectionTicks,
HeartbeatTick: 1,
Storage: s,
MaxSizePerMsg: maxSizePerMsg,
MaxInflightMsgs: maxInflightMsgs,
}
n = raft.StartNode(c, peers)
raftStatusMu.Lock()
raftStatus = n.Status
raftStatusMu.Unlock()
advanceTicksForElection(n, c.ElectionTick)
return
}
func restartNode(cfg *ServerConfig, snapshot *raftpb.Snapshot) (types.ID, *cluster, raft.Node, *raft.MemoryStorage, *wal.WAL) {
var walsnap walpb.Snapshot
if snapshot != nil {
walsnap.Index, walsnap.Term = snapshot.Metadata.Index, snapshot.Metadata.Term
}
w, id, cid, st, ents := readWAL(cfg.WALDir(), walsnap)
plog.Infof("restarting member %s in cluster %s at commit index %d", id, cid, st.Commit)
cl := newCluster("")
cl.SetID(cid)
s := raft.NewMemoryStorage()
if snapshot != nil {
s.ApplySnapshot(*snapshot)
}
s.SetHardState(st)
s.Append(ents)
c := &raft.Config{
ID: uint64(id),
ElectionTick: cfg.ElectionTicks,
HeartbeatTick: 1,
Storage: s,
MaxSizePerMsg: maxSizePerMsg,
MaxInflightMsgs: maxInflightMsgs,
}
n := raft.RestartNode(c)
raftStatusMu.Lock()
raftStatus = n.Status
raftStatusMu.Unlock()
advanceTicksForElection(n, c.ElectionTick)
return id, cl, n, s, w
}
func restartAsStandaloneNode(cfg *ServerConfig, snapshot *raftpb.Snapshot) (types.ID, *cluster, raft.Node, *raft.MemoryStorage, *wal.WAL) {
var walsnap walpb.Snapshot
if snapshot != nil {
walsnap.Index, walsnap.Term = snapshot.Metadata.Index, snapshot.Metadata.Term
}
w, id, cid, st, ents := readWAL(cfg.WALDir(), walsnap)
// discard the previously uncommitted entries
for i, ent := range ents {
if ent.Index > st.Commit {
plog.Infof("discarding %d uncommitted WAL entries ", len(ents)-i)
ents = ents[:i]
break
}
}
// force append the configuration change entries
toAppEnts := createConfigChangeEnts(getIDs(snapshot, ents), uint64(id), st.Term, st.Commit)
ents = append(ents, toAppEnts...)
// force commit newly appended entries
err := w.Save(raftpb.HardState{}, toAppEnts)
if err != nil {
plog.Fatalf("%v", err)
}
if len(ents) != 0 {
st.Commit = ents[len(ents)-1].Index
}
plog.Printf("forcing restart of member %s in cluster %s at commit index %d", id, cid, st.Commit)
cl := newCluster("")
cl.SetID(cid)
s := raft.NewMemoryStorage()
if snapshot != nil {
s.ApplySnapshot(*snapshot)
}
s.SetHardState(st)
s.Append(ents)
c := &raft.Config{
ID: uint64(id),
ElectionTick: cfg.ElectionTicks,
HeartbeatTick: 1,
Storage: s,
MaxSizePerMsg: maxSizePerMsg,
MaxInflightMsgs: maxInflightMsgs,
}
n := raft.RestartNode(c)
raftStatus = n.Status
return id, cl, n, s, w
}
// getIDs returns an ordered set of IDs included in the given snapshot and
// the entries. The given snapshot/entries can contain two kinds of
// ID-related entry:
// - ConfChangeAddNode, in which case the contained ID will be added into the set.
// - ConfChangeRemoveNode, in which case the contained ID will be removed from the set.
func getIDs(snap *raftpb.Snapshot, ents []raftpb.Entry) []uint64 {
ids := make(map[uint64]bool)
if snap != nil {
for _, id := range snap.Metadata.ConfState.Nodes {
ids[id] = true
}
}
for _, e := range ents {
if e.Type != raftpb.EntryConfChange {
continue
}
var cc raftpb.ConfChange
pbutil.MustUnmarshal(&cc, e.Data)
switch cc.Type {
case raftpb.ConfChangeAddNode:
ids[cc.NodeID] = true
case raftpb.ConfChangeRemoveNode:
delete(ids, cc.NodeID)
case raftpb.ConfChangeUpdateNode:
// do nothing
default:
plog.Panicf("ConfChange Type should be either ConfChangeAddNode or ConfChangeRemoveNode!")
}
}
sids := make(types.Uint64Slice, 0)
for id := range ids {
sids = append(sids, id)
}
sort.Sort(sids)
return []uint64(sids)
}
// createConfigChangeEnts creates a series of Raft entries (i.e.
// EntryConfChange) to remove the set of given IDs from the cluster. The ID
// `self` is _not_ removed, even if present in the set.
// If `self` is not inside the given ids, it creates a Raft entry to add a
// default member with the given `self`.
func createConfigChangeEnts(ids []uint64, self uint64, term, index uint64) []raftpb.Entry {
ents := make([]raftpb.Entry, 0)
next := index + 1
found := false
for _, id := range ids {
if id == self {
found = true
continue
}
cc := &raftpb.ConfChange{
Type: raftpb.ConfChangeRemoveNode,
NodeID: id,
}
e := raftpb.Entry{
Type: raftpb.EntryConfChange,
Data: pbutil.MustMarshal(cc),
Term: term,
Index: next,
}
ents = append(ents, e)
next++
}
if !found {
m := Member{
ID: types.ID(self),
RaftAttributes: RaftAttributes{PeerURLs: []string{"http://localhost:7001", "http://localhost:2380"}},
}
ctx, err := json.Marshal(m)
if err != nil {
plog.Panicf("marshal member should never fail: %v", err)
}
cc := &raftpb.ConfChange{
Type: raftpb.ConfChangeAddNode,
NodeID: self,
Context: ctx,
}
e := raftpb.Entry{
Type: raftpb.EntryConfChange,
Data: pbutil.MustMarshal(cc),
Term: term,
Index: next,
}
ents = append(ents, e)
}
return ents
}