raft: add flow control for progress

Each progress has a inflighs sliding window. When the progress
is in replicate state, inflights will control the sending speed
of the leader.

The leader can have at most maxInflight number of inflight
messages for each replicate progress. Receving a appResp moves
forward the sliding window. Heartbeat response free one
slot if the window is full.
This commit is contained in:
Xiang Li 2015-03-19 18:06:51 -07:00
parent ed81ccc1bb
commit 4a64373225
5 changed files with 434 additions and 15 deletions

View File

@ -55,12 +55,22 @@ type Progress struct {
// this Progress will be paused. raft will not resend snapshot until the pending one
// is reported to be failed.
PendingSnapshot uint64
// inflights is a sliding window for the inflight messages.
// When inflights is full, no more message should be sent.
// When sends out a message, the index of the last entry should
// be add to inflights. The index MUST be added into inflights
// in order.
// When receives a reply, the previous inflights should be freed
// by calling inflights.freeTo.
ins *inflights
}
func (pr *Progress) resetState(state ProgressStateType) {
pr.Paused = false
pr.PendingSnapshot = 0
pr.State = state
pr.ins.reset()
}
func (pr *Progress) becomeProbe() {
@ -135,7 +145,16 @@ func (pr *Progress) resume() { pr.Paused = false }
// isPaused returns whether progress stops sending message.
func (pr *Progress) isPaused() bool {
return pr.State == ProgressStateProbe && pr.Paused || pr.State == ProgressStateSnapshot
switch pr.State {
case ProgressStateProbe:
return pr.Paused
case ProgressStateReplicate:
return pr.ins.full()
case ProgressStateSnapshot:
return true
default:
panic("unexpected state")
}
}
func (pr *Progress) snapshotFailure() { pr.PendingSnapshot = 0 }
@ -149,3 +168,62 @@ func (pr *Progress) maybeSnapshotAbort() bool {
func (pr *Progress) String() string {
return fmt.Sprintf("next = %d, match = %d, state = %s, waiting = %v, pendingSnapshot = %d", pr.Next, pr.Match, pr.State, pr.isPaused(), pr.PendingSnapshot)
}
type inflights struct {
// the starting index in the buffer
start int
// number of inflights in the buffer
count int
// the size of the buffer
size int
buffer []uint64
}
func newInflights(size int) *inflights {
return &inflights{
size: size,
buffer: make([]uint64, size),
}
}
// add adds an inflight into inflights
func (in *inflights) add(inflight uint64) {
if in.full() {
panic("cannot add into a full inflights")
}
next := in.start + in.count
if next >= in.size {
next -= in.size
}
in.buffer[next] = inflight
in.count++
}
// freeTo frees the inflights smaller or equal to the given `to` flight.
func (in *inflights) freeTo(to uint64) {
for i := in.start; i < in.start+in.count; i++ {
idx := i
if i >= in.size {
idx -= in.size
}
if to < in.buffer[idx] {
in.count -= i - in.start
in.start = idx
break
}
}
}
func (in *inflights) freeFirstOne() { in.freeTo(in.buffer[in.start]) }
// full returns true if the inflights is full.
func (in *inflights) full() bool {
return in.count == in.size
}
// resets frees all inflights.
func (in *inflights) reset() {
in.count = 0
in.start = 0
}

175
raft/progress_test.go Normal file
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@ -0,0 +1,175 @@
// 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 raft
import (
"reflect"
"testing"
)
func TestInflightsAdd(t *testing.T) {
// no rotating case
in := &inflights{
size: 10,
buffer: make([]uint64, 10),
}
for i := 0; i < 5; i++ {
in.add(uint64(i))
}
wantIn := &inflights{
start: 0,
count: 5,
size: 10,
// ↓------------
buffer: []uint64{0, 1, 2, 3, 4, 0, 0, 0, 0, 0},
}
if !reflect.DeepEqual(in, wantIn) {
t.Fatalf("in = %+v, want %+v", in, wantIn)
}
for i := 5; i < 10; i++ {
in.add(uint64(i))
}
wantIn2 := &inflights{
start: 0,
count: 10,
size: 10,
// ↓---------------------------
buffer: []uint64{0, 1, 2, 3, 4, 5, 6, 7, 8, 9},
}
if !reflect.DeepEqual(in, wantIn2) {
t.Fatalf("in = %+v, want %+v", in, wantIn2)
}
// rotating case
in2 := &inflights{
start: 5,
size: 10,
buffer: make([]uint64, 10),
}
for i := 0; i < 5; i++ {
in2.add(uint64(i))
}
wantIn21 := &inflights{
start: 5,
count: 5,
size: 10,
// ↓------------
buffer: []uint64{0, 0, 0, 0, 0, 0, 1, 2, 3, 4},
}
if !reflect.DeepEqual(in2, wantIn21) {
t.Fatalf("in = %+v, want %+v", in2, wantIn21)
}
for i := 5; i < 10; i++ {
in2.add(uint64(i))
}
wantIn22 := &inflights{
start: 5,
count: 10,
size: 10,
// -------------- ↓------------
buffer: []uint64{5, 6, 7, 8, 9, 0, 1, 2, 3, 4},
}
if !reflect.DeepEqual(in2, wantIn22) {
t.Fatalf("in = %+v, want %+v", in2, wantIn22)
}
}
func TestInflightFreeTo(t *testing.T) {
// no rotating case
in := newInflights(10)
for i := 0; i < 10; i++ {
in.add(uint64(i))
}
in.freeTo(4)
wantIn := &inflights{
start: 5,
count: 5,
size: 10,
// ↓------------
buffer: []uint64{0, 1, 2, 3, 4, 5, 6, 7, 8, 9},
}
if !reflect.DeepEqual(in, wantIn) {
t.Fatalf("in = %+v, want %+v", in, wantIn)
}
in.freeTo(8)
wantIn2 := &inflights{
start: 9,
count: 1,
size: 10,
// ↓
buffer: []uint64{0, 1, 2, 3, 4, 5, 6, 7, 8, 9},
}
if !reflect.DeepEqual(in, wantIn2) {
t.Fatalf("in = %+v, want %+v", in, wantIn2)
}
// rotating case
for i := 10; i < 15; i++ {
in.add(uint64(i))
}
in.freeTo(12)
wantIn3 := &inflights{
start: 3,
count: 2,
size: 10,
// ↓-----
buffer: []uint64{10, 11, 12, 13, 14, 5, 6, 7, 8, 9},
}
if !reflect.DeepEqual(in, wantIn3) {
t.Fatalf("in = %+v, want %+v", in, wantIn3)
}
}
func TestInflightFreeFirstOne(t *testing.T) {
in := newInflights(10)
for i := 0; i < 10; i++ {
in.add(uint64(i))
}
in.freeFirstOne()
wantIn := &inflights{
start: 1,
count: 9,
size: 10,
// ↓------------------------
buffer: []uint64{0, 1, 2, 3, 4, 5, 6, 7, 8, 9},
}
if !reflect.DeepEqual(in, wantIn) {
t.Fatalf("in = %+v, want %+v", in, wantIn)
}
}

View File

@ -59,8 +59,9 @@ type raft struct {
// the log
raftLog *raftLog
maxMsgSize uint64
prs map[uint64]*Progress
maxInflight int
maxMsgSize uint64
prs map[uint64]*Progress
state StateType
@ -109,13 +110,14 @@ func newRaft(id uint64, peers []uint64, election, heartbeat int, storage Storage
// TODO(xiang): add a config arguement into newRaft after we add
// the max inflight message field.
maxMsgSize: 4 * 1024 * 1024,
maxInflight: 256,
prs: make(map[uint64]*Progress),
electionTimeout: election,
heartbeatTimeout: heartbeat,
}
r.rand = rand.New(rand.NewSource(int64(id)))
for _, p := range peers {
r.prs[p] = &Progress{Next: 1}
r.prs[p] = &Progress{Next: 1, ins: newInflights(r.maxInflight)}
}
if !isHardStateEqual(hs, emptyState) {
r.loadState(hs)
@ -195,7 +197,9 @@ func (r *raft) sendAppend(to uint64) {
switch pr.State {
// optimistically increase the next when in ProgressStateReplicate
case ProgressStateReplicate:
pr.optimisticUpdate(m.Entries[n-1].Index)
last := m.Entries[n-1].Index
pr.optimisticUpdate(last)
pr.ins.add(last)
case ProgressStateProbe:
pr.pause()
default:
@ -265,7 +269,7 @@ func (r *raft) reset(term uint64) {
r.elapsed = 0
r.votes = make(map[uint64]bool)
for i := range r.prs {
r.prs[i] = &Progress{Next: r.raftLog.lastIndex() + 1}
r.prs[i] = &Progress{Next: r.raftLog.lastIndex() + 1, ins: newInflights(r.maxInflight)}
if i == r.id {
r.prs[i].Match = r.raftLog.lastIndex()
}
@ -456,6 +460,8 @@ func stepLeader(r *raft, m pb.Message) {
case pr.State == ProgressStateSnapshot && pr.maybeSnapshotAbort():
raftLogger.Infof("raft: %x snapshot aborted, resumed sending replication messages to %x [%s]", r.id, m.From, pr)
pr.becomeProbe()
case pr.State == ProgressStateReplicate:
pr.ins.freeTo(m.Index)
}
if r.maybeCommit() {
@ -468,6 +474,10 @@ func stepLeader(r *raft, m pb.Message) {
}
}
case pb.MsgHeartbeatResp:
// free one slot for the full inflights window to allow progress.
if pr.State == ProgressStateReplicate && pr.ins.full() {
pr.ins.freeFirstOne()
}
if pr.Match < r.raftLog.lastIndex() {
r.sendAppend(m.From)
}
@ -661,7 +671,7 @@ func (r *raft) removeNode(id uint64) {
func (r *raft) resetPendingConf() { r.pendingConf = false }
func (r *raft) setProgress(id, match, next uint64) {
r.prs[id] = &Progress{Next: next, Match: match}
r.prs[id] = &Progress{Next: next, Match: match, ins: newInflights(r.maxInflight)}
}
func (r *raft) delProgress(id uint64) {

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@ -0,0 +1,155 @@
// 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 raft
import (
"testing"
pb "github.com/coreos/etcd/raft/raftpb"
)
// TestMsgAppFlowControlFull ensures:
// 1. msgApp can fill the sending window until full
// 2. when the window is full, no more msgApp can be sent.
func TestMsgAppFlowControlFull(t *testing.T) {
r := newRaft(1, []uint64{1, 2}, 5, 1, NewMemoryStorage(), 0)
r.becomeCandidate()
r.becomeLeader()
pr2 := r.prs[2]
// force the progress to be in replicate state
pr2.becomeReplicate()
// fill in the inflights window
for i := 0; i < r.maxInflight; i++ {
r.Step(pb.Message{From: 1, To: 1, Type: pb.MsgProp, Entries: []pb.Entry{{Data: []byte("somedata")}}})
ms := r.readMessages()
if len(ms) != 1 {
t.Fatalf("#%d: len(ms) = %d, want 1", i, len(ms))
}
}
// ensure 1
if !pr2.ins.full() {
t.Fatalf("inflights.full = %t, want %t", pr2.ins.full(), true)
}
// ensure 2
for i := 0; i < 10; i++ {
r.Step(pb.Message{From: 1, To: 1, Type: pb.MsgProp, Entries: []pb.Entry{{Data: []byte("somedata")}}})
ms := r.readMessages()
if len(ms) != 0 {
t.Fatalf("#%d: len(ms) = %d, want 0", i, len(ms))
}
}
}
// TestMsgAppFlowControlMoveForward ensures msgAppResp can move
// forward the sending window correctly:
// 1. vaild msgAppResp.index moves the windows to pass all smaller or equal index.
// 2. out-of-dated msgAppResp has no effect on the silding window.
func TestMsgAppFlowControlMoveForward(t *testing.T) {
r := newRaft(1, []uint64{1, 2}, 5, 1, NewMemoryStorage(), 0)
r.becomeCandidate()
r.becomeLeader()
pr2 := r.prs[2]
// force the progress to be in replicate state
pr2.becomeReplicate()
// fill in the inflights window
for i := 0; i < r.maxInflight; i++ {
r.Step(pb.Message{From: 1, To: 1, Type: pb.MsgProp, Entries: []pb.Entry{{Data: []byte("somedata")}}})
r.readMessages()
}
// 1 is noop, 2 is the first proposal we just sent.
// so we start with 2.
for tt := 2; tt < r.maxInflight; tt++ {
// move forward the window
r.Step(pb.Message{From: 2, To: 1, Type: pb.MsgAppResp, Index: uint64(tt)})
r.readMessages()
// fill in the inflights window again
r.Step(pb.Message{From: 1, To: 1, Type: pb.MsgProp, Entries: []pb.Entry{{Data: []byte("somedata")}}})
ms := r.readMessages()
if len(ms) != 1 {
t.Fatalf("#%d: len(ms) = %d, want 1", tt, len(ms))
}
// ensure 1
if !pr2.ins.full() {
t.Fatalf("inflights.full = %t, want %t", pr2.ins.full(), true)
}
// ensure 2
for i := 0; i < tt; i++ {
r.Step(pb.Message{From: 2, To: 1, Type: pb.MsgAppResp, Index: uint64(i)})
if !pr2.ins.full() {
t.Fatalf("#%d: inflights.full = %t, want %t", tt, pr2.ins.full(), true)
}
}
}
}
// TestMsgAppFlowControlRecvHeartbeat ensures a heartbeat response
// frees one slot if the window is full.
func TestMsgAppFlowControlRecvHeartbeat(t *testing.T) {
r := newRaft(1, []uint64{1, 2}, 5, 1, NewMemoryStorage(), 0)
r.becomeCandidate()
r.becomeLeader()
pr2 := r.prs[2]
// force the progress to be in replicate state
pr2.becomeReplicate()
// fill in the inflights window
for i := 0; i < r.maxInflight; i++ {
r.Step(pb.Message{From: 1, To: 1, Type: pb.MsgProp, Entries: []pb.Entry{{Data: []byte("somedata")}}})
r.readMessages()
}
for tt := 1; tt < 5; tt++ {
if !pr2.ins.full() {
t.Fatalf("#%d: inflights.full = %t, want %t", tt, pr2.ins.full(), true)
}
// recv tt msgHeartbeatResp and expect one free slot
for i := 0; i < tt; i++ {
r.Step(pb.Message{From: 2, To: 1, Type: pb.MsgHeartbeatResp})
r.readMessages()
if pr2.ins.full() {
t.Fatalf("#%d.%d: inflights.full = %t, want %t", tt, i, pr2.ins.full(), false)
}
}
// one slot
r.Step(pb.Message{From: 1, To: 1, Type: pb.MsgProp, Entries: []pb.Entry{{Data: []byte("somedata")}}})
ms := r.readMessages()
if len(ms) != 1 {
t.Fatalf("#%d: free slot = 0, want 1", tt)
}
// and just one slot
for i := 0; i < 10; i++ {
r.Step(pb.Message{From: 1, To: 1, Type: pb.MsgProp, Entries: []pb.Entry{{Data: []byte("somedata")}}})
ms1 := r.readMessages()
if len(ms1) != 0 {
t.Fatalf("#%d.%d: len(ms) = %d, want 0", tt, i, len(ms1))
}
}
// clear all pending messages.
r.Step(pb.Message{From: 2, To: 1, Type: pb.MsgHeartbeatResp})
r.readMessages()
}
}

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@ -48,24 +48,24 @@ func (r *raft) readMessages() []pb.Message {
return msgs
}
func TestBecomeProbe(t *testing.T) {
func TestProgressBecomeProbe(t *testing.T) {
match := uint64(1)
tests := []struct {
p *Progress
wnext uint64
}{
{
&Progress{State: ProgressStateReplicate, Match: match, Next: 5},
&Progress{State: ProgressStateReplicate, Match: match, Next: 5, ins: newInflights(256)},
2,
},
{
// snapshot finish
&Progress{State: ProgressStateSnapshot, Match: match, Next: 5, PendingSnapshot: 10},
&Progress{State: ProgressStateSnapshot, Match: match, Next: 5, PendingSnapshot: 10, ins: newInflights(256)},
11,
},
{
// snapshot failure
&Progress{State: ProgressStateSnapshot, Match: match, Next: 5, PendingSnapshot: 0},
&Progress{State: ProgressStateSnapshot, Match: match, Next: 5, PendingSnapshot: 0, ins: newInflights(256)},
2,
},
}
@ -83,8 +83,8 @@ func TestBecomeProbe(t *testing.T) {
}
}
func TestBecomeReplicate(t *testing.T) {
p := &Progress{State: ProgressStateProbe, Match: 1, Next: 5}
func TestProgressBecomeReplicate(t *testing.T) {
p := &Progress{State: ProgressStateProbe, Match: 1, Next: 5, ins: newInflights(256)}
p.becomeReplicate()
if p.State != ProgressStateReplicate {
@ -98,8 +98,8 @@ func TestBecomeReplicate(t *testing.T) {
}
}
func TestBecomeSnapshot(t *testing.T) {
p := &Progress{State: ProgressStateProbe, Match: 1, Next: 5}
func TestProgressBecomeSnapshot(t *testing.T) {
p := &Progress{State: ProgressStateProbe, Match: 1, Next: 5, ins: newInflights(256)}
p.becomeSnapshot(10)
if p.State != ProgressStateSnapshot {
@ -234,6 +234,7 @@ func TestProgressIsPaused(t *testing.T) {
p := &Progress{
State: tt.state,
Paused: tt.paused,
ins: newInflights(256),
}
if g := p.isPaused(); g != tt.w {
t.Errorf("#%d: shouldwait = %t, want %t", i, g, tt.w)