go version go1.11.2 Darwin/amd64
我有以下代码示例,为SO演示目的而创建:
package main
import (
...
)
type T struct {
ctx context.Context
ch1 chan string
}
func New(ctx context.Context) *T {
t := &T{ctx: ctx}
go t.run(2)
return t
}
func (t *T) run(workers int) {
t.ch1 = make(chan string)
done := make(chan struct{})
go func() {
<-t.ctx.Done()
close(done)
close(t.ch1)
}()
for i := 0; i < workers; i++ {
go func() {
for {
select {
case <-done:
return
case m, ok := <-t.ch1:
if ok {
t.process(done, m)
}
}
}
}()
}
}
func (t *T) process(done <-chan struct{}, s string) {
select {
case <-done:
return
default:
log.Printf("processing %s", s)
time.Sleep(time.Millisecond * 200)
}
}
func (t *T) Read() <-chan string {
return t.ch1
}
func (t *T) Write(s string) error {
select {
case <-t.ctx.Done():
return errors.New("consumer is closed today")
case t.ch1 <- s:
return nil
}
}
func main() {
ctx, cancel := context.WithCancel(context.Background())
t := New(ctx)
go func() {
for m := range t.Read() {
log.Printf("got %s", m)
}
<-ctx.Done()
}()
for i := 0; i < 10; i++ {
t.Write(strconv.Itoa(i))
}
cancel()
}
当我使用种族检测器构建并运行它时,它会抛出以下数据竞赛:
go build -race ./test/ && ./test
==================
WARNING: DATA RACE
Read at 0x00c0000b6030 by goroutine 7:
main.main.func1()
/redacted/test/app.go:60 +0x42
Previous write at 0x00c0000b6030 by goroutine 6:
main.(*T).run()
/redacted/test/app.go:24 +0x6a
Goroutine 7 (running) created at:
main.main()
/redacted/test/app.go:76 +0xbc
Goroutine 6 (running) created at:
main.New()
/redacted/test/app.go:18 +0xcd
main.main()
/redacted/test/app.go:74 +0x86
==================
==================
WARNING: DATA RACE
Read at 0x00c0000b6030 by main goroutine:
main.(*T).Write()
/redacted/test/app.go:67 +0x8a
main.main()
/redacted/test/app.go:84 +0xdc
Previous write at 0x00c0000b6030 by goroutine 6:
main.(*T).run()
/redacted/test/app.go:24 +0x6a
Goroutine 6 (running) created at:
main.New()
/redacted/test/app.go:18 +0xcd
main.main()
/redacted/test/app.go:74 +0x86
==================
2019/01/20 10:48:51 got 0
2019/01/20 10:48:51 got 3
2019/01/20 10:48:51 processing 1
2019/01/20 10:48:51 processing 2
2019/01/20 10:48:51 got 4
2019/01/20 10:48:51 got 5
2019/01/20 10:48:51 got 6
2019/01/20 10:48:51 got 7
2019/01/20 10:48:51 got 8
2019/01/20 10:48:51 got 9
Found 2 data race(s)
我遇到的问题是,我似乎找不到一种方法让用户在频道中输入内容,而不公开任何用于写入的频道,没有比赛。这怎么可能?我缺少的有更好的模式吗?
我建议进行以下更改:
- 在
New
中分配给ch1
,以避免在多个 goroutines 中读取和写入t.ch1
的竞赛 - 只有在所有对
Write
的呼叫完成后才关闭ch1
以避免"在封闭频道上发送"恐慌 - 使用
sync.WaitGroup
在写入所有值后等待所有处理 GoRoutines 完成(以便程序在处理完成之前不会退出)
将这些更改组合在一起,如下所示:
package main
import (
"log"
"strconv"
"sync"
"time"
)
type T struct {
// ch1 receives the values to process
ch1 chan string
// wg is used to wait for the workers to stop
wg sync.WaitGroup
}
func New() *T {
t := &T{
ch1: make(chan string),
}
go t.run(2)
return t
}
func (t *T) run(workers int) {
// add the workers to the WaitGroup
t.wg.Add(workers)
for i := 0; i < workers; i++ {
go func() {
// process values from the channel until it closes
// and then signal to the WaitGroup that we're done
defer t.wg.Done()
for m := range t.ch1 {
t.process(m)
}
}()
}
}
// Stop is called after we're done calling Write and we want to stop the
// processing once all values have been processed
func (t *T) Stop() {
// close t.ch1 so that the workers know to stop processing
close(t.ch1)
// wait for the workers to all finish before returning
t.wg.Wait()
}
func (t *T) process(s string) {
log.Printf("processing %s", s)
time.Sleep(time.Millisecond * 200)
}
func (t *T) Write(s string) {
t.ch1 <- s
}
func main() {
// start the main loop
t := New()
// write 10 values
for i := 0; i < 10; i++ {
t.Write(strconv.Itoa(i))
}
// stop the loop, which will wait for processing to finish before returning
t.Stop()
}