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ϗϦωζϛͰΘ͔Δ
Goroutineೖ
golang.tokyo#14 2018/04/16
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ࣗݾհ
‣ Name: ᅳ ହฏ (Morikuni Taihei)
‣ GitHub: @morikuni
‣ Twitter: @inukirom
‣ ॴଐ
‣ גࣜձࣾϝϧΧϦ
‣ GoͰόοΫΤϯυ։ൃ
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ຊͷ༰
ॳ৺ऀ͕GoroutineΛ͑ΔΑ͏ʹͳΔͨΊͷ
‣ Goʹ͓͚Δฒߦॲཧʹ͍ͭͯ
‣ GoroutineΛͬͨฒߦॲཧͷҙͱରࡦ
‣ ศརͳπʔϧͷհ
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Goʹ͓͚Δฒߦॲཧʹ͍ͭͯ
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GoʹΈࠐ·Ε͍ͯΔฒߦॲཧͷͨΊͷػೳ
‣ Goroutine
‣ chan
‣ select
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Goroutineʹ͍ͭͯ
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Goroutineͱ
‣ GoΛද͢Δػೳͷ1ͭ
‣ ฒߦॲཧΛߦ͏ͨΊͷػೳ(CPU͕ෳ͋Εฒྻ࣮ߦͰ͖Δ)
‣ ϓϩηεεϨουΑΓܰྔ
‣ mainؔGoroutineͱ࣮ͯ͠ߦ͞Ε͍ͯΔ
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Goroutineͷىಈ
go Λ͚ͭͯؔΛݺͼग़͢͜ͱͰGoroutine͕ىಈ͢Δ
go Function()
go obj.Method()
go func() {
fmt.Println("hello goroutine")
}()
go func(name string) {
fmt.Println("hello "+name)
}("morikuni") // ҾͤΔ
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࣮ߦॱংอূ͞Εͳ͍
go func() {
fmt.Println("goroutine 1")
}()
go func() {
fmt.Println("goroutine 2")
}()
go func() {
fmt.Println("goroutine 3")
}()
// goroutine 3
// goroutine 1
// goroutine 2
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GoroutineͱίʔϧελοΫ
‣ Goroutine͕ىಈͨ࣌͠ͰؔͷίʔϧελοΫ͕͢Δ
‣ panicGoroutineͷίʔϧελοΫΛ͍ͬͯ͘
‣ ͭ·Γɺdefer & recoverpanic͕ൃੜͨ͠GoroutineͰ͏ඞཁ͕͋Δ
‣ Devquiz͜Ε͕ϋϚΓϙΠϯτ
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GoroutineͱίʔϧελοΫ
GoroutineΛΘͳ͍߹ͷίʔϧελοΫ
func A() {
B()
}
func B() {
defer func(){}()
C()
}
func C() {
D()
}
func D() {
panic("dead")
}
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GoroutineͱίʔϧελοΫ
func A() {
func B() {
defer func(){}()
func C() {
func D() {
panic("dead")
}
}
}
}
ίʔϧελοΫ: A → B → C → D
Bͷdefer͕࣮ߦ͞ΕΔ
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GoroutineͱίʔϧελοΫ
GoroutineΛͬͨ߹ͷίʔϧελοΫ
func A() {
B()
}
func B() {
defer func(){}()
go C() // goͰݺͼग़͢
}
func C() {
D()
}
func D() {
panic("dead")
}
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GoroutineͱίʔϧελοΫ
func A() {
func B() {
defer func(){}()
}
}
func C() {
func D() {
panic("dead")
}
}
ίʔϧελοΫ: C → D
Bͷdefer࣮ߦ͞Εͳ͍
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chanʹ͍ͭͯ
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chanͱ
‣ Goroutineؒͷσʔλͷૹड৴ॲཧͷಉظΛߦ͏
‣ FIFOͷΩϡʔ(࠷ॳʹೖΕ͕ͨ࠷ॳʹऔΓग़͞ΕΔ)
‣ ༰ྔΛ࣋ͭ
‣ 3छྨͷܕ͕͋Δ
‣ Read Write
‣ Read only
‣ Write only
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chanͷ͍ํ
// chanͷ࡞
c := make(chan int)
// chanͷॻ͖ࠐΈ
c <- 1
// chan͔ΒͷಡΈࠐΈ
x := <- c
for x := range c {
...
}
// chanΛด͡Δ
close(c)
ดͨ͡chan͔Βθϩ͕ಡΈࠐΊΔΑ͏ʹͳΓɺforϧʔϓ͕ऴྃ͢Δ
ดͨ͡chanʹॻ͖ࠐΉͱpanic͢Δ
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chanͷܕ
c := make(chan int) // RW chan
func Publish(c chan <- int) { // WO chan
...
}
func Subscribe(c <-chan int) { // RO chan
...
}
// RW chanWOͱROʹೖՄೳ
Publish(c)
Subscribe(c)
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selectʹ͍ͭͯ
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selectͱ
‣ ෳͷchanͷૢ࡞Λѻ͏ͨΊͷͷ
‣ ࣮ߦՄೳʹͳͬͨchanͷૢ࡞Λ1͚࣮ͭͩߦ͢Δ
‣ defaultΛॻ͘͜ͱͰchanͷϒϩοΫΛ͛Δ
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selectͷ͍ํ
select {
case v := <-c1:
fmt.Println(v)
case c2 <- "hello":
}
c1͔ΒͷಡΈࠐΈ or c2ͷॻ͖ࠐΈͷͲͪΒ͔Λ࣮ߦ͢Δ
࣮ߦͰ͖Δ·ͰϒϩοΫ͢Δ
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selectͷ͍ํ
select {
case v := <-c1:
fmt.Println(v)
case c2 <- "hello":
default:
fmt.Println("not ready")
}
c1͔ΒͷಡΈࠐΈc2ͷॻ͖ࠐΈͰ͖ͳ͍߹ʹdefault͕࣮ߦ͞ΕΔ
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͜͜·Ͱ͕Goʹ͓͚Δฒߦॲཧͷجૅ
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GoroutineΛͬͨ
ฒߦॲཧͷҙͱରࡦ
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Waitॲཧ
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Waitॲཧ
func main() {
go func() {
fmt.Println("Hello World")
}()
}
ͳʹ͕ग़ྗ͞ΕΔͰ͠ΐ͏ʁ
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Waitॲཧ
$ go run main.go
(ͳʹग़ྗ͞Εͳ͍)
ͳͥʁ
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Waitॲཧ
Goroutineͷॲཧ͕࣮ߦ͞ΕΔલʹϓϩηε͕ऴྃͯ͠͠·͏͔Β
func main() {
go func() {
fmt.Println("Hello World")
}()
}
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Waitॲཧ
ରࡦ1: Sleep͢Δ
func main() {
go func() {
fmt.Println("Hello World")
}()
time.Sleep(time.Second)
}
ॲཧ͕ऴΘͬͨͷʹͪଓ͚Δ͜ͱʹͳΔ
ॻ͖ࣺͯͷίʔυͰΑ͘͏
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Waitॲཧ
ରࡦ2: channelΛ͏
func main() {
c := make(chan struct{})
go func() {
defer func() { c <- struct{}{} }()
fmt.Println("Hello World")
}()
<-c // close͞ΕΔ·Ͱͭ
}
chanͰॲཧͷྃΛ௨͢Δ
deferͰඞ࣮ͣߦ͞ΕΔΑ͏ʹ͢Δ
chan boolΛ͏Α͏ͳྫ͋Δ͚Ͳɺstruct{}ͷ΄͏͕Ұൠత
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Waitॲཧ
ରࡦ3: sync.WaitGroupΛ͏
func main() {
var wg sync.WaitGroup
wg.Add(1) // GoroutineΛݺͼग़͢લʹAdd͢Δ
go func() {
defer wg.Done() // GoroutineͷதͰdeferΛͬͯDoneΛݺͼग़͢
fmt.Println("Hello World")
}()
wg.Wait()
}
WaitGroup෦ͷΧϯλ͕0ʹͳΔ·Ͱwait͢Δ
Done() = Add(-1)ͳͷͰAdd͚ͨͩ͠Done͢Δඞཁ͕͋Δ
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Waitॲཧͷ·ͱΊ
‣ αϯϓϧίʔυͳͲtime.Sleepָ͕
‣ جຊతʹsync.WaitGroupΛ͍ͬͯΕ͍͍
‣ chanෳͷGoroutineͷྃΛͭͷʹ͍ͮΒ͍
‣ golang.org/x/sync/errgroupͱ͍͏WaitGroupʹΤϥʔॲཧΛՃͨ͠
ͷ͋Δ
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Goroutineͱforϧʔϓ
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Goroutineͱforϧʔϓ
1, 2, 3, 4, 5Λग़ྗ͍ͨ͠(ॱෆಉ)
xs := []int{1, 2, 3, 4, 5}
for _, x := range xs {
go func() {
fmt.Println(x)
}()
}
time.Sleep(time.Second)
ͳʹ͕ग़ྗ͞ΕΔͰ͠ΐ͏ʁ
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Goroutineͱforϧʔϓ
$ go run main.go
5
5
5
5
5
ͳͥʁ
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Goroutineͱforϧʔϓ
xϧʔϓຖʹΛ্ॻ͖͞Ε͍ͯճ͞ΕΔ͔Β
xs := []int{1, 2, 3, 4, 5}
for _, x := range xs {
go func() {
fmt.Println(x)
}()
}
time.Sleep(time.Second)
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Goroutineͱforϧʔϓ
forͷ࣮Πϝʔδ
func iterate(xs []int, x *int) func() {
i := -1
return func() {
i ++
*x = xs[i]
}
}
xs := []int{1, 2, 3, 4, 5}
var x int
next := iterator(xs, &x)
for i := 0; i < len(xs); i ++ {
next()
go func() {
fmt.Println(x)
}()
}
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Goroutineͱforϧʔϓ
ରࡦ: Ұมʹೖ͢Δ
for _, x := range xs {
go func(x int) { // ؔͷҾͰ͏͚ͱΔ
fmt.Println(x)
}(x)
}
for _, x := range xs {
x := x // ผͷมʹೖ͢Δ
go func() {
fmt.Println(x)
}()
}
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ڝ߹ঢ়ଶ
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ڝ߹ঢ়ଶ
xsͷΛ2ഒͯ͠doubleʹॻ͖ࠐΈ͍ͨ(ॱෆಉ)
xs := []int{1, 2, 3, 4, 5}
var double []int
for _, x := range xs {
go func(x int) {
double = append(double, x*2)
}(x)
}
time.Sleep(time.Second)
fmt.Println(double)
ͳʹ͕ग़ྗ͞ΕΔͰ͠ΐ͏ʁ
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ڝ߹ঢ়ଶ
$ go run main.go
[2 10]
$ go run main.go
[4 2 6 8 10]
$ go run main.go
[4 2 8]
ͳͥʁ
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ڝ߹ঢ়ଶ
doubleΛಡΈࠐΜͰɺॻ͖ࠐΉ·Ͱʹdouble͕ߋ৽͞Ε͍ͯΔ͔Β
for _, x := range xs {
go func(x int) {
double = append(double, x*2)
}(x)
}
࣮ࡍʹಡΈࠐΈ͔Βॻ͖ࠐΈ·Ͱʹ͕͔͔͍࣌ؒͬͯΔ
for _, x := range xs {
go func(x int) {
tmp := double
tmp = append(tmp, x*2)
double = tmp
}(x)
}
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ڝ߹ঢ়ଶ
R: double͔ΒಡΈࠐΜͩ
W: doubleʹॻ͖ࠐΉ
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ڝ߹ঢ়ଶ
ରࡦ1: Ͱॲཧ͢Δ
‣ ฒߦॲཧΛ͢Δͱڝ߹͕͓͖ΔͷͰɺഉଞ੍ޚΛߦ͏
‣ ഉଞ੍ޚΛҰ൪؆୯ʹΔํ๏ɺྻͰॲཧ͢Δ͜ͱͳͷͰຊʹGoroutine
͏ඞཁ͕͋Δ͔Λݕ౼ͯ͠ΈΔͱ͍͍
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ڝ߹ঢ়ଶ
ରࡦ2: sync.MutexΛ͏
var mu sync.Mutex
xs := []int{1, 2, 3, 4, 5}
for _, x := range xs {
go func(x int) {
mu.Lock()
defer mu.Unlock()
double = append(double, x*2)
}(x)
}
Ұʹmu.Lock()Ͱ͖Δͷ1Օॴ͚ͩ
ଞͷՕॴmu.Unlock()͞ΕΔ·ͰϒϩοΫ͞ΕΔ
sync.RWMutexΛ͏ͱɺಡΈࠐΈͱॻ͖ࠐΈͷLockΛ͚ͯಡΈࠐΈฒߦͰ
ߦ͑Δ
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ڝ߹ঢ়ଶ
ओʹܥ: sync/atomicύοέʔδΛ͏
var count int64
atomic.AddInt64(&count, 1) // countʹ1Λ͢
atomic.CompareAndSwapInt64(&count, 1, 10) // countͷ͕1ͳΒ10ʹ͢Δ
v := atomic.LoadInt64(&count) // countͷΛಡΈࠐΉ
atomic.StoreInt64(&count, 100) // countͷΛ100ʹ͢Δ
float64ͳͲαϙʔτ͞Ε͍ͯͳ͍͕ؤுΕ͑Δ
(floatΛ෦తʹuintͱͯ͠ѻ͍ɺmath.Float64frombitsͱ
atomic.LoadUint64ͳͲΛΈ߹ΘͤΔ)
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ڝ߹ঢ়ଶͷ·ͱΊ
‣ ྻॲཧ(Goroutine͔ͭΘͳ͍)Ͱμϝ͔ݕ౼
‣ ܥsync/atomic͕͑ΔՄೳੑ͕͋Δ
‣ ͦΕҎ֎sync.Mutex, sync.RWMutexΛ͑େମͳ͍
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Goroutine leak
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Goroutine leak
websiteAͱwebsiteBͷͲͪΒ͔ͷ݁ՌΛग़ྗ͍ͨ͠
type result struct {
Response *http.Response
Err error
}
func fetch(url string, c chan <- result) {
res, err := http.Get(url)
c <- result{res, err}
}
ch := make(chan result)
go fetch("https: //websiteA", ch)
go fetch("https: //websiteB", ch)
fmt.Println( <-ch) // ࠷ॳʹฦ͖ͬͯͨํ͚ͩΛ͏
ͳʹ͕ʹͳΔͰ͠ΐ͏ʁ
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Goroutine leak
type result struct {
Response *http.Response
Err error
}
func fetch(url string, c chan <- result) {
res, err := http.Get(url)
c <- result{res, err}
}
ch := make(chan result)
go fetch("https: //websiteA", ch)
go fetch("https: //websiteB", ch)
fmt.Println( <-ch) // ࠷ॳʹฦ͖ͬͯͨํ͚ͩΛ͏
websiteAͱwebsiteBͷͲͪΒ͔ยํͷGoroutine͕leak͢Δ
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Goroutine leak
ରࡦ: context.ContextͱselectΛ͏
func fetch(ctx context.Context, url string, result chan <- *http.Response) {
res, err := http.Get(url) // ΄ΜͱGetcontextΛͬͨํ͕͍͍͚ͲྫͳͷͰׂѪ
select {
case c <- result{res, err}
case <-ctx.Done(): // context͕͍ྃͯͨ͠ΒॲཧΛΊΔ
}
}
ctx, cancel := context.WithCancel(context.Background())
defer cancel() // ྃޙʹcancelͯ͠contextΛdoneঢ়ଶʹ͢Δ
ch := make(chan *http.Response)
go fetch(ctx, "https: //websiteA", ch)
go fetch(ctx, "https: //websiteB", ch)
fmt.Println( <-ch) // ࠷ॳʹฦ͖ͬͯͨํ͚ͩΛ͏
websiteA͕ྃ → fmt.Println → defer cancel() →
ctx.Done() → websiteBͷfetch͕ऴྃ → Goroutine͕ऴྃ
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GoroutineΛͬͨฒߦॲཧͷҙͱରࡦͷ·ͱΊ
‣ forͰมʹೖ͢Δ
‣ sync.WaitGroupͰྃΛͭ
‣ sync.MutexͰഉଞ੍ޚΛ͢Δ
‣ ܥsync/atomic͕ศར
‣ context.ContextͰGoroutine leakΛճආ͢Δ
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ศརͳπʔϧͷհ
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gotrace
‣ https://github.com/divan/gotrace
‣ GoroutineͱchanͷΓͱΓΛՄࢹԽͰ͖Δ
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gotraceͷ͍ํ
gotraceίϚϯυΛΠϯετʔϧ͢Δ
ͨͿΜmasterϒϥϯνͩͱಈ͔ͳ͍
$ go get -u https: //github.com/divan/gotrace
$ cd $(GOPATH)/github.com/divan/gotrace
$ git checkout -b go18 origin/go18
$ go install
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gotraceͷ͍ํ
ՄࢹԽ͍ͨؔ͠ͷઌ಄ʹ͜ΕΛॻ͘
import "runtime/trace"
f, err := os.Create("trace.out")
if err != nil {
log.Fatal(err)
}
defer f.Close()
trace.Start(f)
defer trace.Stop()
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gotraceͷ͍ํ
gotraceͰՄࢹԽ͢Δ
ύονΛͯͨGoΛ͏ඞཁ͕͋ΔͷͰdockerΛ͏
$ cd path/to/main # main.go͕͋ΔσΟϨΫτϦ
$ docker run --rm -it \
-e GOOS=darwin \
-v (pwd):/src \
divan/golang:gotrace \
go build -o /src/binary /src/main.go
$ ./binary
$ gotrace ./trace.out
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gotraceΛಈ͔ͯ͠ΈΔ
func Publish(c chan <- int) {
c <- 1
time.Sleep(time.Millisecond)
c <- 2
time.Sleep(time.Millisecond)
c <- 3
time.Sleep(time.Millisecond)
}
func Subscribe(c <-chan int) {
for v := range c {
fmt.Println(v)
}
}
func main() {
f, err := os.Create("trace.out")
if err != nil {
log.Fatal(err)
}
defer f.Close()
trace.Start(f)
defer trace.Stop()
c := make(chan int, 0)
go Publish(c)
go Subscribe(c)
time.Sleep(5 * time.Millisecond)
}
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gotraceΛಈ͔ͯ͠ΈΔ
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Goroutine leakͱ͔ݟ͔ͭΔ͔?
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ࠓͷ·ͱΊ
‣ GoݴޠతʹฒߦॲཧΛαϙʔτ͍ͯ͠Δ
‣ ฒߦॲཧ͍͚͠Ͳ͋ΔఔύλʔϯԽͰ͖Δ
‣ syncܥύοέʔδศར
‣ gotraceָ͍͠(খฒײ)
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ʕ◔ϖ◔ʔ < Goroutine͍͖ͬͯ