目录结构
代码语言：javascript复制$ tree -d -L 1
.
├── api
├── builder
├── cli
├── client
├── cmd # 命令行的入口，我们就要从这里跳进去看
├── container # 容器的抽象
├── contrib # 杂物堆，啥杂七杂八的都往这里丢
├── daemon # 今天的主角，dockerd这个daemon
├── distribution # 看起来发布相关的
├── dockerversion
├── docs # 文档
├── errdefs # 一些常见的错误
├── hack
├── image # 镜像的抽象概念
├── integration
├── integration-cli
├── internal
├── layer # 层。怎么说呢，就是对各种layer fs的抽象
├── libcontainerd
├── migrate
├── oci # https://blog.docker.com/2017/07/demystifying-open-container-initiative-oci-specifications/ 容器标准库相关
├── opts # 一些配置和配置校验相关的
├── pkg # 类似于我们平时写的utils或者helpers等
├── plugin # 插件相关的东西
├── profiles
├── project
├── reference
├── registry
├── reports
├── restartmanager # 负责容器的重启，比如是否设置了"always"呀
├── runconfig
├── vendor # go的vendor机制
└── volume # volume相关- 负责存储配置的一般都叫
xx Store - Docker的设计是单机的，不是分布式的
- Docker的设计是Client-Server模式的，平时我们用的docker这个命令被分散到 https://github.com/docker/cli 这个仓库去了
从命令行进入
入口在 cmd/dockerd/docker.go:
func newDaemonCommand() *cobra.Command {
opts := newDaemonOptions(config.New())
cmd := &cobra.Command{
Use: "dockerd [OPTIONS]",
Short: "A self-sufficient runtime for containers.",
SilenceUsage: true,
SilenceErrors: true,
Args: cli.NoArgs,
RunE: func(cmd *cobra.Command, args []string) error {
if opts.version {
showVersion()
return nil
}
opts.flags = cmd.Flags()
return runDaemon(opts) // 真正的入口
},
}
cli.SetupRootCommand(cmd)
flags := cmd.Flags()
flags.BoolVarP(&opts.version, "version", "v", false, "Print version information and quit")
flags.StringVar(&opts.configFile, "config-file", defaultDaemonConfigFile, "Daemon configuration file")
opts.InstallFlags(flags)
installConfigFlags(opts.daemonConfig, flags)
installServiceFlags(flags)
return cmd
}然后跳到 cmd/dockerd/daemon.go：
func (cli *DaemonCli) start(opts *daemonOptions) (err error) {
stopc := make(chan bool)
defer close(stopc)
// warn from uuid package when running the daemon
uuid.Loggerf = logrus.Warnf
// 设置一些默认配置例如TLS啊blabla
opts.SetDefaultOptions(opts.flags)
// 加载配置
if cli.Config, err = loadDaemonCliConfig(opts); err != nil {
return err
}
cli.configFile = &opts.configFile
cli.flags = opts.flags
if cli.Config.Debug {
debug.Enable()
}
if cli.Config.Experimental {
logrus.Warn("Running experimental build")
}
logrus.SetFormatter(&logrus.TextFormatter{
TimestampFormat: jsonmessage.RFC3339NanoFixed,
DisableColors: cli.Config.RawLogs,
FullTimestamp: true,
})
// LCOW: Linux Containers On Windows. ref: https://blog.docker.com/2017/09/preview-linux-containers-on-windows/
system.InitLCOW(cli.Config.Experimental)
// 设置默认的umask。022。也就是说，创建的文件权限都是755
if err := setDefaultUmask(); err != nil {
return fmt.Errorf("Failed to set umask: %v", err)
}
// Create the daemon root before we create ANY other files (PID, or migrate keys)
// to ensure the appropriate ACL is set (particularly relevant on Windows)
// 设置daemon的执行时候的根目录
if err := daemon.CreateDaemonRoot(cli.Config); err != nil {
return err
}
if cli.Pidfile != "" {
pf, err := pidfile.New(cli.Pidfile)
if err != nil {
return fmt.Errorf("Error starting daemon: %v", err)
}
defer func() {
if err := pf.Remove(); err != nil {
logrus.Error(err)
}
}()
}
// TODO: extract to newApiServerConfig()
serverConfig := &apiserver.Config{
Logging: true,
SocketGroup: cli.Config.SocketGroup,
Version: dockerversion.Version,
CorsHeaders: cli.Config.CorsHeaders,
}
// 是否走TLS
if cli.Config.TLS {
tlsOptions := tlsconfig.Options{
CAFile: cli.Config.CommonTLSOptions.CAFile,
CertFile: cli.Config.CommonTLSOptions.CertFile,
KeyFile: cli.Config.CommonTLSOptions.KeyFile,
ExclusiveRootPools: true,
}
if cli.Config.TLSVerify {
// server requires and verifies client's certificate
tlsOptions.ClientAuth = tls.RequireAndVerifyClientCert
}
tlsConfig, err := tlsconfig.Server(tlsOptions)
if err != nil {
return err
}
serverConfig.TLSConfig = tlsConfig
}
if len(cli.Config.Hosts) == 0 {
cli.Config.Hosts = make([]string, 1)
}
cli.api = apiserver.New(serverConfig)
var hosts []string
// 设置API server
for i := 0; i < len(cli.Config.Hosts); i {
var err error
if cli.Config.Hosts[i], err = dopts.ParseHost(cli.Config.TLS, cli.Config.Hosts[i]); err != nil {
return fmt.Errorf("error parsing -H %s : %v", cli.Config.Hosts[i], err)
}
protoAddr := cli.Config.Hosts[i]
protoAddrParts := strings.SplitN(protoAddr, "://", 2)
if len(protoAddrParts) != 2 {
return fmt.Errorf("bad format %s, expected PROTO://ADDR", protoAddr)
}
proto := protoAddrParts[0]
addr := protoAddrParts[1]
// It's a bad idea to bind to TCP without tlsverify.
if proto == "tcp" && (serverConfig.TLSConfig == nil || serverConfig.TLSConfig.ClientAuth != tls.RequireAndVerifyClientCert) {
logrus.Warn("[!] DON'T BIND ON ANY IP ADDRESS WITHOUT setting --tlsverify IF YOU DON'T KNOW WHAT YOU'RE DOING [!]")
}
ls, err := listeners.Init(proto, addr, serverConfig.SocketGroup, serverConfig.TLSConfig)
if err != nil {
return err
}
ls = wrapListeners(proto, ls)
// If we're binding to a TCP port, make sure that a container doesn't try to use it.
if proto == "tcp" {
if err := allocateDaemonPort(addr); err != nil {
return err
}
}
logrus.Debugf("Listener created for HTTP on %s (%s)", proto, addr)
hosts = append(hosts, protoAddrParts[1])
cli.api.Accept(addr, ls...)
}
registryService, err := registry.NewService(cli.Config.ServiceOptions)
if err != nil {
return err
}
rOpts, err := cli.getRemoteOptions()
if err != nil {
return fmt.Errorf("Failed to generate containerd options: %s", err)
}
containerdRemote, err := libcontainerd.New(filepath.Join(cli.Config.Root, "containerd"), filepath.Join(cli.Config.ExecRoot, "containerd"), rOpts...)
if err != nil {
return err
}
signal.Trap(func() {
cli.stop()
<-stopc // wait for daemonCli.start() to return
}, logrus.StandardLogger())
// Notify that the API is active, but before daemon is set up.
preNotifySystem()
pluginStore := plugin.NewStore()
// 初始化中间件
if err := cli.initMiddlewares(cli.api, serverConfig, pluginStore); err != nil {
logrus.Fatalf("Error creating middlewares: %v", err)
}
// 实例化daemon
d, err := daemon.NewDaemon(cli.Config, registryService, containerdRemote, pluginStore)
if err != nil {
return fmt.Errorf("Error starting daemon: %v", err)
}
d.StoreHosts(hosts)
// validate after NewDaemon has restored enabled plugins. Dont change order.
if err := validateAuthzPlugins(cli.Config.AuthorizationPlugins, pluginStore); err != nil {
return fmt.Errorf("Error validating authorization plugin: %v", err)
}
// TODO: move into startMetricsServer()
if cli.Config.MetricsAddress != "" {
if !d.HasExperimental() {
return fmt.Errorf("metrics-addr is only supported when experimental is enabled")
}
if err := startMetricsServer(cli.Config.MetricsAddress); err != nil {
return err
}
}
// TODO: createAndStartCluster()
name, _ := os.Hostname()
// Use a buffered channel to pass changes from store watch API to daemon
// A buffer allows store watch API and daemon processing to not wait for each other
watchStream := make(chan *swarmapi.WatchMessage, 32)
// 默认就初始化Docker Swarm？
c, err := cluster.New(cluster.Config{
Root: cli.Config.Root,
Name: name,
Backend: d,
ImageBackend: d.ImageService(),
PluginBackend: d.PluginManager(),
NetworkSubnetsProvider: d,
DefaultAdvertiseAddr: cli.Config.SwarmDefaultAdvertiseAddr,
RaftHeartbeatTick: cli.Config.SwarmRaftHeartbeatTick,
RaftElectionTick: cli.Config.SwarmRaftElectionTick,
RuntimeRoot: cli.getSwarmRunRoot(),
WatchStream: watchStream,
})
if err != nil {
logrus.Fatalf("Error creating cluster component: %v", err)
}
d.SetCluster(c)
err = c.Start()
if err != nil {
logrus.Fatalf("Error starting cluster component: %v", err)
}
// Restart all autostart containers which has a swarm endpoint
// and is not yet running now that we have successfully
// initialized the cluster.
d.RestartSwarmContainers()
logrus.Info("Daemon has completed initialization")
cli.d = d
// 注册handler到router
routerOptions, err := newRouterOptions(cli.Config, d)
if err != nil {
return err
}
routerOptions.api = cli.api
routerOptions.cluster = c
// 初始化router
initRouter(routerOptions)
// process cluster change notifications
watchCtx, cancel := context.WithCancel(context.Background())
defer cancel()
go d.ProcessClusterNotifications(watchCtx, watchStream)
cli.setupConfigReloadTrap()
// The serve API routine never exits unless an error occurs
// We need to start it as a goroutine and wait on it so
// daemon doesn't exit
serveAPIWait := make(chan error)
// 开始执行
go cli.api.Wait(serveAPIWait)
// after the daemon is done setting up we can notify systemd api
// 还要通知systemd？
notifySystem()
// Daemon is fully initialized and handling API traffic
// Wait for serve API to complete
// api server停了，daemon就跟着退出
errAPI := <-serveAPIWait
c.Cleanup()
shutdownDaemon(d)
containerdRemote.Cleanup()
if errAPI != nil {
return fmt.Errorf("Shutting down due to ServeAPI error: %v", errAPI)
}
return nil
}这里做的事情可就多了，加载配置，设置相关的变量和配置，监听端口，设置信号handler， 起了API server，等待接受请求。
创建容器
上面我们看到了daemon的启动过程。启动完之后就等待请求了。那我们要找一个新的入口点去跟踪 代码，所以我选择 docker run。从 docker/cli 库翻了翻，发现最后是调用 containers/create 这样一个接口。然后就在本仓库里搜索，我们的目标是找到处理这个请求的mux所在地，然后翻出对应的 handler api/server/router/container/container.go，然后跳到 api/server/router/container/container_routes.go:
ccr, err := s.backend.ContainerCreate(types.ContainerCreateCo
nfig{
Name: name,
Config: config,
HostConfig: hostConfig,
NetworkingConfig: networkingConfig,
AdjustCPUShares: adjustCPUShares,
})跳进去，发现是个接口。而 s.backend 其实就是daemon。具体代码在上一节就可以跟到。所以我打开fzf进行 泛搜索 func daemon ContainerCreate，找到了 daemon/create.go ：
// ContainerCreate creates a regular container
// 创建一个容器
func (daemon *Daemon) ContainerCreate(params types.ContainerCreateConfig) (containertypes.ContainerCreateCreatedBody, error) {
return daemon.containerCreate(params, false)
}
func (daemon *Daemon) containerCreate(params types.ContainerCreateConfig, managed bool) (containertypes.ContainerCreateCreatedBody, error) {
start := time.Now()
if params.Config == nil {
return containertypes.ContainerCreateCreatedBody{}, errdefs.InvalidParameter(errors.New("Config cannot be empty in order to create a container"))
}
os := runtime.GOOS // 不知道这个是干啥的。。。Windows和Linux怎么混来混去的。。。
if params.Config.Image != "" {
// 拉取镜像
img, err := daemon.imageService.GetImage(params.Config.Image)
if err == nil {
os = img.OS
}
} else {
// This mean scratch. On Windows, we can safely assume that this is a linux
// container. On other platforms, it's the host OS (which it already is)
if runtime.GOOS == "windows" && system.LCOWSupported() {
os = "linux"
}
}
// 验证容器的配置，如果有问题，就不能创建
warnings, err := daemon.verifyContainerSettings(os, params.HostConfig, params.Config, false)
if err != nil {
return containertypes.ContainerCreateCreatedBody{Warnings: warnings}, errdefs.InvalidParameter(err)
}
// 验证网络配置
err = verifyNetworkingConfig(params.NetworkingConfig)
if err != nil {
return containertypes.ContainerCreateCreatedBody{Warnings: warnings}, errdefs.InvalidParameter(err)
}
if params.HostConfig == nil {
params.HostConfig = &containertypes.HostConfig{}
}
// 调整一些配置，例如CPU如果超量了，就设置成系统允许的最大的。等。
err = daemon.adaptContainerSettings(params.HostConfig, params.AdjustCPUShares)
if err != nil {
return containertypes.ContainerCreateCreatedBody{Warnings: warnings}, errdefs.InvalidParameter(err)
}
// 创建容器
container, err := daemon.create(params, managed)
if err != nil {
return containertypes.ContainerCreateCreatedBody{Warnings: warnings}, err
}
containerActions.WithValues("create").UpdateSince(start)
return containertypes.ContainerCreateCreatedBody{ID: container.ID, Warnings: warnings}, nil
}
// Create creates a new container from the given configuration with a given name.
// 创建容器
func (daemon *Daemon) create(params types.ContainerCreateConfig, managed bool) (retC *container.Container, retErr error) {
var (
container *container.Container
img *image.Image
imgID image.ID
err error
)
os := runtime.GOOS
if params.Config.Image != "" {
img, err = daemon.imageService.GetImage(params.Config.Image)
if err != nil {
return nil, err
}
if img.OS != "" {
os = img.OS
} else {
// default to the host OS except on Windows with LCOW
if runtime.GOOS == "windows" && system.LCOWSupported() {
os = "linux"
}
}
imgID = img.ID()
if runtime.GOOS == "windows" && img.OS == "linux" && !system.LCOWSupported() {
return nil, errors.New("operating system on which parent image was created is not Windows")
}
} else {
// 没搞懂这个分支在这干啥。。。
if runtime.GOOS == "windows" {
os = "linux" // 'scratch' case.
}
}
// 再次检查配置
if err := daemon.mergeAndVerifyConfig(params.Config, img); err != nil {
return nil, errdefs.InvalidParameter(err)
}
if err := daemon.mergeAndVerifyLogConfig(¶ms.HostConfig.LogConfig); err != nil {
return nil, errdefs.InvalidParameter(err)
}
// 创建容器。。。。这个嵌套的有点多。。。此处返回的是内存中对容器的一个抽象 `Container`
if container, err = daemon.newContainer(params.Name, os, params.Config, params.HostConfig, imgID, managed); err != nil {
return nil, err
}
defer func() {
if retErr != nil {
if err := daemon.cleanupContainer(container, true, true); err != nil {
logrus.Errorf("failed to cleanup container on create error: %v", err)
}
}
}()
if err := daemon.setSecurityOptions(container, params.HostConfig); err != nil {
return nil, err
}
container.HostConfig.StorageOpt = params.HostConfig.StorageOpt
// Fixes: https://github.com/moby/moby/issues/34074 and
// https://github.com/docker/for-win/issues/999.
// Merge the daemon's storage options if they aren't already present. We only
// do this on Windows as there's no effective sandbox size limit other than
// physical on Linux.
if runtime.GOOS == "windows" {
if container.HostConfig.StorageOpt == nil {
container.HostConfig.StorageOpt = make(map[string]string)
}
for _, v := range daemon.configStore.GraphOptions {
opt := strings.SplitN(v, "=", 2)
if _, ok := container.HostConfig.StorageOpt[opt[0]]; !ok {
container.HostConfig.StorageOpt[opt[0]] = opt[1]
}
}
}
// Set RWLayer for container after mount labels have been set
// 要创建一个RWLayer，这样容器里面才可以读写。前面的layer都包含在image里。
rwLayer, err := daemon.imageService.CreateLayer(container, setupInitLayer(daemon.idMappings))
if err != nil {
return nil, errdefs.System(err)
}
container.RWLayer = rwLayer
rootIDs := daemon.idMappings.RootPair()
if err := idtools.MkdirAndChown(container.Root, 0700, rootIDs); err != nil {
return nil, err
}
if err := idtools.MkdirAndChown(container.CheckpointDir(), 0700, rootIDs); err != nil {
return nil, err
}
if err := daemon.setHostConfig(container, params.HostConfig); err != nil {
return nil, err
}
if err := daemon.createContainerOSSpecificSettings(container, params.Config, params.HostConfig); err != nil {
return nil, err
}
var endpointsConfigs map[string]*networktypes.EndpointSettings
if params.NetworkingConfig != nil {
endpointsConfigs = params.NetworkingConfig.EndpointsConfig
}
// Make sure NetworkMode has an acceptable value. We do this to ensure
// backwards API compatibility.
runconfig.SetDefaultNetModeIfBlank(container.HostConfig)
daemon.updateContainerNetworkSettings(container, endpointsConfigs)
if err := daemon.Register(container); err != nil {
return nil, err
}
stateCtr.set(container.ID, "stopped")
daemon.LogContainerEvent(container, "create")
return container, nil
}然后跟到 daemon.create，仔细看，然后继续跟到了 daemon.newContainer ：
func (daemon *Daemon) newContainer(name string, operatingSystem string, config *containertypes.Config, hostConfig *containertypes.HostConfig, imgID image.ID, managed bool) (*container.Container, error) {
var (
id string
err error
noExplicitName = name == ""
)
id, name, err = daemon.generateIDAndName(name)
if err != nil {
return nil, err
}
if hostConfig.NetworkMode.IsHost() {
if config.Hostname == "" {
config.Hostname, err = os.Hostname()
if err != nil {
return nil, errdefs.System(err)
}
}
} else {
// 原来容器的hostname默认是容器id的前12位
daemon.generateHostname(id, config)
}
entrypoint, args := daemon.getEntrypointAndArgs(config.Entrypoint, config.Cmd)
base := daemon.newBaseContainer(id) // 瞧。。。又一个创建容器
base.Created = time.Now().UTC()
base.Managed = managed
base.Path = entrypoint
base.Args = args //FIXME: de-duplicate from config
base.Config = config
base.HostConfig = &containertypes.HostConfig{}
base.ImageID = imgID
base.NetworkSettings = &network.Settings{IsAnonymousEndpoint: noExplicitName}
base.Name = name
base.Driver = daemon.imageService.GraphDriverForOS(operatingSystem)
base.OS = operatingSystem
return base, err
}整个流程就跟完了。
