为什么goroutine停顿了几分钟

时间:2018-12-26 06:45:51

标签: go amazon-s3 concurrency goroutine

我有一个用GO编写的任务,可以从AWS S3读取.gz文件,每个.gz文件的大小为 20M

每个goroutine将从.s3文件中下载一个.gz文件到本地磁盘,然后通过gzip.NewReader逐行读取其内容。

当任务(goroutine)计数超过70时,67个goroutine将成功完成其操作。但是剩下的goroutine将被 暂停 几分钟。

在它暂停的那一刻,我看到CPU为100%,然后,CPU将降低到0.2%(4CPU,16G内存)以保持几分钟。

问题 :我很困惑,为什么那时goroutines在CPU相当低的情况下什么也不做?可能是什么原因造成的?

Test results:
60 goroutines, it will finish successfully in 27 seconds;
70 goroutines, it will finish successfully in 30s;
80 goroutines, 77 of them will finish successfully in 30s, but the remaining 3 will **pause 4 minutes**, then restart and finish in 10s

代码如下:

主要goroutine:

    func main() {
      runtime.GOMAXPROCS(runtime.NumCPU()*2)
      chs := make([]chan string, 70)
      for i:=min; i<max; i++ {
          chs[i] = make(chan string, 1)
          go readobj.Reads3obj(i, chs[i])
      }
      for _, ch := range chs {
        fmt.Println(<-ch)
      }
    }

ReadObject:

func Reads3obj(s3KeyName, ch chan string) {
    sess, err := session.NewSession(&aws.Config{
              Region: aws.String("x"),
              Credentials: credentials.NewStaticCredentials("x", "x", "")},)

    downloader := s3manager.NewDownloader(sess)

    //create a zipFile to download from S3 to local
    zipFile, err := os.Create(zipname)

    //download .gz file from S3
    n, err := downloader.Download(zipFile, &s3.GetObjectInput{
        Bucket: aws.String(bucket),
        Key:    aws.String(s3KeyName),
    })
    //create a file reader
    fileReader, err := os.Open(zipFile)

    //create a gzip reader      
    gzipReader, err := gzip.NewReader(fileReader)

    //create a buffered reader
    buf := bufio.NewReader(gzipReader)

    //read zip file line by line
    for line, isPrefix, err := []byte{0}, false, error(nil); len(line) > 0 && err == nil; {
        line, isPrefix, err = buf.ReadLine()
       //insert line to ES
    }
  }

编辑: 暂停时,打开的文件数量非常少,所以我认为打开的文件没有超过最大数量,这无关紧要。因为:

ll /proc/PID/fd的输出是

zc@ip-xxx:/proc/18059/fd$ ll
total 0
dr-x------ 2 zc zc  0 Dec 26 06:50 ./
dr-xr-xr-x 9 zc zc  0 Dec 26 06:50 ../
lrwx------ 1 zc zc 64 Dec 26 06:50 0 -> /dev/pts/0
lrwx------ 1 zc zc 64 Dec 26 06:50 1 -> /dev/pts/0
lrwx------ 1 zc zc 64 Dec 26 06:50 12 -> 
/home/zc/75.gz
lrwx------ 1 zc zc 64 Dec 26 06:50 2 -> /dev/pts/0
lrwx------ 1 zc zc 64 Dec 26 06:50 21 -> 
/home/zc/78.gz
lrwx------ 1 zc zc 64 Dec 26 06:50 253 -> socket:[76054]
lrwx------ 1 zc zc 64 Dec 26 06:50 280 -> socket:[77064]
lrwx------ 1 zc zc 64 Dec 26 06:50 47 -> 
/home/zc/58.gz
lrwx------ 1 zc zc 64 Dec 26 06:50 65 -> anon_inode:[eventpoll]
lrwx------ 1 zc zc 64 Dec 26 06:50 93 -> socket:[75984]

1 个答案:

答案 0 :(得分:0)

Golang gzip库在一个goroutine中读取文件

如此大的文件会长时间100%占用cpu。请改用pzip

用作gzip的替代品,交换

  import "compress/gzip" 

 import gzip "github.com/klauspost/pgzip".