Schwarzeni

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Docker相关进程结构

只是一个简答的分析，有一个大概的认识，其实我还看了一会儿Docker的源码，然后看的自闭了

环境

  • Version: 19.03.2
  • OS/Arch: linux/amd64
  • （这里使用的是安装K8S时附带安装的Docker）

Docker相关进程名称

这里仅列出进程名称：

  • dockerd
  • containerd
  • containerd-shim
  • docker-proxy

实验环境准备

为了能更加明显地观察到这些进程的关系，本地启动两个 Nginx 容器

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docker run -p 8081:80 -d nginx:alpine
docker run -p 8082:80 -d nginx:alpine

查看结果

执行命令查看相关的进程

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pstree -apl | grep 'container\|docker' -A3 -B3

截取了主要的部分结果如下！

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  |-containerd,926
  |   |-containerd-shim,3334 -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/f25d014e124b01669e0d5d518b7759efcf0a9be898774870a89af8a126ad9402 -address /run/containerd/containerd.sock -containerd-binary /usr/bin/containerd -runtime-root /var/run/docker/runtime-runc
  |   |   |-nginx,3358
  |   |   |   |-nginx,3430
  |   |   |   `-nginx,3431
  |   |   |-{containerd-shim},3335
  |   |   |-{containerd-shim},3336
  |   |   |-{containerd-shim},3337
  |   |   |-{containerd-shim},3338
  |   |   |-{containerd-shim},3339
  |   |   |-{containerd-shim},3340
  |   |   |-{containerd-shim},3341
  |   |   |-{containerd-shim},3390
  |   |   `-{containerd-shim},4654
  |   |-containerd-shim,4393 -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/54a64603063ff0260b98bfe6196f9304455ef14dd762565f48dc708ea7314ac2 -address /run/containerd/containerd.sock -containerd-binary /usr/bin/containerd -runtime-root /var/run/docker/runtime-runc
  |   |   |-nginx,4422
  |   |   |   |-nginx,4477
  |   |   |   `-nginx,4478
  |   |   |-{containerd-shim},4394
  |   |   |-{containerd-shim},4395
  |   |   |-{containerd-shim},4396
  |   |   |-{containerd-shim},4397
  |   |   |-{containerd-shim},4398
  |   |   |-{containerd-shim},4399
  |   |   |-{containerd-shim},4400
  |   |   |-{containerd-shim},4401
  |   |   `-{containerd-shim},5501
  |   |-{containerd},1035
  |   |-{containerd},1036
  |   |-{containerd},1037
  |   |-{containerd},1038
  |   |-{containerd},1112
  |   |-{containerd},1124
  |   |-{containerd},1169
  |   |-{containerd},1170
  |   |-{containerd},2118
  |   |-{containerd},2119
  |   |-{containerd},2120
  |   `-{containerd},4466
--
  |-dockerd,1914 -H unix:// -H tcp://0.0.0.0:2375
  |   |-docker-proxy,3326 -proto tcp -host-ip 0.0.0.0 -host-port 8082 -container-ip 172.17.0.2 -container-port 80
  |   |   |-{docker-proxy},3327
  |   |   |-{docker-proxy},3328
  |   |   |-{docker-proxy},3329
  |   |   |-{docker-proxy},3330
  |   |   |-{docker-proxy},3331
  |   |   `-{docker-proxy},3332
  |   |-docker-proxy,4386 -proto tcp -host-ip 0.0.0.0 -host-port 8081 -container-ip 172.17.0.3 -container-port 80
  |   |   |-{docker-proxy},4387
  |   |   |-{docker-proxy},4388
  |   |   |-{docker-proxy},4389
  |   |   |-{docker-proxy},4390
  |   |   |-{docker-proxy},4391
  |   |   `-{docker-proxy},4392
  |   |-{dockerd},1975
  |   |-{dockerd},1976
  |   |-{dockerd},1977
  |   |-{dockerd},1980
  |   |-{dockerd},1991
  |   |-{dockerd},1992
  |   |-{dockerd},2091
  |   |-{dockerd},2115
  |   |-{dockerd},2172
  |   |-{dockerd},2173
  |   `-{dockerd},2174

{dockerd} 代表进程 dockerd 开出的子线程

分析结构图

看上面的这个图已经非常清晰了：

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  |-containerd,926
  |   |-containerd-shim,3334 -namespace moby -workdir...
  |   |   |-nginx,3358
  |   |   |   |-nginx,3430
  |   |   |   `-nginx,3431
  |   |   |-{containerd-shim},3335
// ...
  |   |   `-{containerd-shim},4654
  |   |-containerd-shim,4393 -namespace moby -workdir...
  |   |   |-nginx,4422
  |   |   |   |-nginx,4477
  |   |   |   `-nginx,4478
  |   |   |-{containerd-shim},4394
// ...
  |   |   `-{containerd-shim},5501
  |   |-{containerd},1035
// ....

从上述关系可以看出， containerd 启动了子进程 containerd-shim 以及一些线程， containerd-shim 启动了容器的进程以及一些线程。每启动一个容器就需要启动一个 containerd-shim ，可见 containerd-shim 与容器有着紧密的联系。

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 |-dockerd,1914 -H unix:// -H tcp://0.0.0.0:2375
  |   |-docker-proxy,3326 -proto tcp -host-ip 0.0.0.0 -host-port 8082 -container-ip 172.17.0.2 -container-port 80
  |   |   |-{docker-proxy},3327
// ...
  |   |   `-{docker-proxy},3332
  |   |-docker-proxy,4386 -proto tcp -host-ip 0.0.0.0 -host-port 8081 -container-ip 172.17.0.3 -container-port 80
  |   |   |-{docker-proxy},4387
// ...
  |   |   `-{docker-proxy},4392
  |   |-{dockerd},1975
// ...
  |   `-{dockerd},2174

从上述关系可以看出， dockerd 启动了 docker-proxy 以及多个子线程，而 docker-proxy 负责传输相应的数据到指定的容器中，本次实验中使用的是 host 模式。

那么， 进程 dockerd 与 containerd 的父进程是多少？可以使用 pstree -s -p {PID} 查看，但这里还有一种方法，查看文件 /proc/{PID}/stat 中的第四个参数，两者都为 1 ，也就是 systemd 启动的它们.