解决国产系统 Docker 拉取大镜像卡顿之谜

$ docker pull xxx:5000/xxxx
xxx: Pulling from xxx/xxxxxx
7c0b344a74c2: Extracting [>                                                  ]  294.9kB/26.66MB
7c0b344a74c2: Download complete
e53ed7fd3110: Download complete
d2cae797bc79: Download complete
ec3ddc176f08: Download complete
2969517e196e: Download complete
097fa64722e8: Download complete
1dde4ca01a5a: Download complete

$ docker info
...
 Server Version: 19.03.15
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Native Overlay Diff: true
 Logging Driver: json-file
 Cgroup Driver: cgroupfs
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
 Swarm: inactive
 Runtimes: runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: ea765aba0d05254012b0b9e595e995c09186427f
 runc version: v1.0.0-0-g84113eef
 init version: fec3683
 Security Options:
  seccomp
   Profile: default
 Kernel Version: 4.19.90-2211.5.0.0178.22.uel20.aarch64
 Operating System: UnionTech OS Server 20
 OSType: linux
 Architecture: aarch64
 CPUs: 24
 Total Memory: 94.56GiB
 Name: host-xxxx
 ID: RTQS:5TXE:5T3S:YW7X:OHPK:FZ7D:7EHD:DH5Z:JNBV:FVXS:24FA:EIVS
 Docker Root Dir: /data/kube/docker
 Debug Mode: true
  File Descriptors: 29
  Goroutines: 46
  System Time: 2023-04-12T16:10:25.33362426+08:00
$ uname -a
Linux host-x 4.19.90-2211.5.0.0178.22.uel20.aarch64 #1 SMP Thu Nov 24 10:33:07 CST 2022 aarch64 aarch64 aarch64 GNU/Linux
$ cat /etc/os-release
PRETTY_NAME="UnionTech OS Server 20"
NAME="UnionTech OS Server 20"
VERSION_ID="20"
VERSION="20"
ID=uos
HOME_URL="https://www.chinauos.com/"
BUG_REPORT_URL="https://bbs.chinauos.com/"
VERSION_CODENAME=fuyu
PLATFORM_ID="platform:uel20"

$ pstree -sp 1170083
systemd(1)───dockerd(1169795)───unpigz(1170083)─┬─{unpigz}(1170084)
                                                ├─{unpigz}(1170086)
                                                └─{unpigz}(1170087)

failed to register layer: Error processing tar file(exit status 1): unexpected EOF

// https://github.com/moby/moby/blob/v19.03.15/pkg/chrootarchive/archive_unix.go#L90-L116
 cmd := reexec.Command("docker-untar", dest, root)
  ...
 if err := cmd.Wait(); err != nil {
  // when `xz -d -c -q | docker-untar ...` failed on docker-untar side,
  // we need to exhaust `xz`'s output, otherwise the `xz` side will be
  // pending on write pipe forever
  io.Copy(ioutil.Discard, decompressedArchive)

  return fmt.Errorf("Error processing tar file(%v): %s", err, output)
 }
 return nil

$ xargs -0 < /proc/1170083/cmdline
/usr/bin/unpigz -d -c
$ ps aux | grep docker-unta[r]
root     1164788  0.0  0.0 1491008 39488 pts/2   Sl+  15:21   0:00 docker-untar / /data/kube/docker/overlay2/546b7b992b53b243450807b8150c4a1905e93afae604da69a21bbaaf443f178e/diff

// https://github.com/moby/moby/blob/v19.03.15/pkg/archive/archive.go#L32-L39
func init() {
 if path, err := exec.LookPath("unpigz"); err != nil {
  logrus.Debug("unpigz binary not found in PATH, falling back to go gzip library")
 } else {
  logrus.Debugf("Using unpigz binary found at path %s", path)
  unpigzPath = path
 }
}

// https://github.com/moby/moby/blob/v19.03.15/pkg/archive/archive.go#L160-L174
func gzDecompress(ctx context.Context, buf io.Reader) (io.ReadCloser, error) {
 if unpigzPath == "" {
  return gzip.NewReader(buf)
 }

 disablePigzEnv := os.Getenv("MOBY_DISABLE_PIGZ")
 if disablePigzEnv != "" {
  if disablePigz, err := strconv.ParseBool(disablePigzEnv); err != nil {
   return nil, err
  } else if disablePigz {
   return gzip.NewReader(buf)
  }
 }

 return cmdStream(exec.CommandContext(ctx, unpigzPath, "-d", "-c"), buf)
}

$ rpm -qf /bin/unpigz
pigz-2.4-7.uel20.01.aarch64
$ rpm -V pigz
# -V 查看包也没被修改

$ systemctl stop docker
# 临时命令行前台 debug 启动下看看是没问题的
$ MOBY_DISABLE_PIGZ=true dockerd --debug