我正在使用以下代码来同步 goroutine。最近在调查一个错误时,我发现下面的代码并不总是有效。大约五分之一的失败。频道 quit
在我的 out
频道之前收到消息。我能够在我的本地(不是在 go-playground)和 k8s 环境中一致地重现这个问题。作为一种解决方法,我现在使用 sync.Map
进行同步。
有没有办法修复下面的代码?
package main
import (
"fmt"
"io/ioutil"
"log"
"os"
"path"
"sync"
"sync/atomic"
"time"
)
func main() {
//test setup
filePaths := []string{
path.Join(os.TempDir(), fmt.Sprint("f1-", time.Now().Nanosecond())),
path.Join(os.TempDir(), fmt.Sprint("f2-", time.Now().Nanosecond())),
path.Join(os.TempDir(), fmt.Sprint("f3-", time.Now().Nanosecond())),
path.Join(os.TempDir(), fmt.Sprint("f4-", time.Now().Nanosecond())),
path.Join(os.TempDir(), fmt.Sprint("f5-", time.Now().Nanosecond())),
path.Join(os.TempDir(), fmt.Sprint("f6-", time.Now().Nanosecond())),
}
for _, filePath := range filePaths {
f, err := os.OpenFile(filePath, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0600)
if err != nil {
log.Fatal(err)
}
_, err = f.WriteString("There are many variations of passages of Lorem Ipsum available, but the majority have suffered alteration in some form, by injected humour, or randomised words which don't look even slightly believable. If you are going to use a passage of Lorem Ipsum, you need to be sure there isn't anything embarrassing hidden in the middle of text. All the Lorem Ipsum generators on the Internet tend to repeat predefined chunks as necessary, making this the first true generator on the Internet. It uses a dictionary of over 200 Latin words, combined with a handful of model sentence structures, to generate Lorem Ipsum which looks reasonable. The generated Lorem Ipsum is therefore always free from repetition, injected humour, or non-characteristic words etc.")
if err != nil {
log.Fatal(err)
}
err = f.Close()
if err != nil {
log.Fatal(err)
}
}
for {
responses, err := getContents(filePaths)
if err != nil {
log.Fatal(err)
}
if len(responses) != len(filePaths) {
log.Fatalf("Responses Does not Match, need %d Got %d",len(filePaths), len(responses))
}
time.Sleep(1 * time.Second)
}
}
func getContents(fileNames []string) ([][]byte, error) {
wg := sync.WaitGroup{}
var responseBytes [][]byte
out := make(chan []byte, 10)
defer close(out)
quit := make(chan int)
var opsFileRead uint64
var opsChannelGot uint64
defer close(quit)
go func() {
for {
select {
case bts := <-out:
if len(bts) > 0 {
atomic.AddUint64(&opsChannelGot, 1)
responseBytes = append(responseBytes, bts)
}
break
case <-quit:
fmt.Printf("I quit, i read %d, i got %d\n", opsFileRead, opsChannelGot)
return
}
}
}()
for _, fileName := range fileNames {
wg.Add(1)
go func(fName string, out chan []byte, wg *sync.WaitGroup) {
defer wg.Done()
data, err := ioutil.ReadFile(fName)
if err != nil {
log.Fatal(err)
}
out <- data
atomic.AddUint64(&opsFileRead, 1)
}(fileName, out, &wg)
}
wg.Wait()
quit <- 1
return responseBytes, nil
}
答案 0 :(得分:5)
当接收到退出时,输出通道可以包含值。通过创建一个无缓冲通道来修复:
out := make(chan []byte)
这确保在退出之前收到从工作人员发送的值:
wg.Done()
之前在无缓冲通道上发送/接收wg.Done()
的所有调用都发生在 wg.Wait()
返回之前wg.Wait()
在值发送到 quit
之前返回因此,在将值发送到 out
之前,先从 quit
接收这些值。
另一种方法是关闭 out
通道以通知结果收集器工作人员已完成:
func getContents(fileNames []string) ([][]byte, error) {
wg := sync.WaitGroup{}
var responseBytes [][]byte
out := make(chan []byte)
var opsFileRead uint64
var opsChannelGot uint64
for _, fileName := range fileNames {
wg.Add(1)
go func(fName string, out chan []byte, wg *sync.WaitGroup) {
defer wg.Done()
data, err := ioutil.ReadFile(fName)
if err != nil {
log.Fatal(err)
}
out <- data
atomic.AddUint64(&opsFileRead, 1)
}(fileName, out, &wg)
}
// Close out after workers are done.
go func() {
wg.Wait()
close(out)
}()
// Loop over outputs until done.
for bts := range out {
if len(bts) > 0 {
atomic.AddUint64(&opsChannelGot, 1)
responseBytes = append(responseBytes, bts)
}
}
fmt.Printf("I quit, i read %d, i got %d\n", opsFileRead, opsChannelGot)
return responseBytes, nil
}