本帖最后由 pig2 于 2014-10-14 09:12 编辑 阅读导读： 1.如何通过docker命令，解析出命令行flag参数，以及docker命令中的请求参数? 2.如何处理具体的flag参数信息，并收集Docker Client所需的配置信息? 3.如何创建一个Docker Client? 4.如何解析docker命令中的请求参数，获取相应请求的类型? 5.Docker Client如何执行具体的请求命令，最终将请求发送至Docker Server? 1. 前言 《Docker源码分析》系列之Docker架构 篇，而本文主要针对后者，从源码的角度分析Docker Client，力求帮助开发者更深刻的理解Docker Client的具体实现，最终更好的掌握Docker Client的使用方法。即本文为《Docker源码分析》系列的第二篇——Docker Client篇。2.Docker Client的创建
2.1. Docker命令的flag参数解析 flag包 ./docker/docker/docker.go func main() {
if reexec.Init() {
return
}
flag.Parse()
// FIXME: validate daemon flags here
……
} 复制代码 reexec.Init() ./docker/docker/flag.go var (
flVersion = flag.Bool([]string{"v", "-version"}, false, "Print version information and quit")
flDaemon = flag.Bool([]string{"d", "-daemon"}, false, "Enable daemon mode")
flDebug = flag.Bool([]string{"D", "-debug"}, false, "Enable debug mode")
flSocketGroup = flag.String([]string{"G", "-group"}, "docker", "Group to assign the unix socket specified by -H when running in daemon mode use '' (the empty string) to disable setting of a group")
flEnableCors = flag.Bool([]string{"#api-enable-cors", "-api-enable-cors"}, false, "Enable CORS headers in the remote API")
flTls = flag.Bool([]string{"-tls"}, false, "Use TLS; implied by tls-verify flags")
flTlsVerify = flag.Bool([]string{"-tlsverify"}, false, "Use TLS and verify the remote (daemon: verify client, client: verify daemon)")
// these are initialized in init() below since their default values depend on dockerCertPath which isn't fully initialized until init() runs
flCa *string
flCert *string
flKey *string
flHosts []string
)
func init() {
flCa = flag.String([]string{"-tlscacert"}, filepath.Join(dockerCertPath, defaultCaFile), "Trust only remotes providing a certificate signed by the CA given here")
flCert = flag.String([]string{"-tlscert"}, filepath.Join(dockerCertPath, defaultCertFile), "Path to TLS certificate file")
flKey = flag.String([]string{"-tlskey"}, filepath.Join(dockerCertPath, defaultKeyFile), "Path to TLS key file")
opts.HostListVar(&flHosts, []string{"H", "-host"}, "The socket(s) to bind to in daemon mode\nspecified using one or more tcp://host:port, unix:///path/to/socket, fd://* or fd://socketfd.")
} 复制代码 命令行参数flag的解析 2.2. 处理flag信息并收集Docker Client的配置信息 if *flVersion {
showVersion()
return
} 复制代码 if *flDebug {
os.Setenv("DEBUG", "1")
} 复制代码 if len(flHosts) == 0 {
defaultHost := os.Getenv("DOCKER_HOST")
if defaultHost == "" || *flDaemon {
// If we do not have a host, default to unix socket
defaultHost = fmt.Sprintf("unix://%s", api.DEFAULTUNIXSOCKET)
}
if _, err := api.ValidateHost(defaultHost); err != nil {
log.Fatal(err)
}
flHosts = append(flHosts, defaultHost)
} 复制代码 ./docker/api/common.go if *flDaemon {
mainDaemon()
return
} 复制代码 if len(flHosts) > 1 {
log.Fatal("Please specify only one -H")
}
protoAddrParts := strings.SplitN(flHosts[0], "://", 2) 复制代码 var (
cli *client.DockerCli
tlsConfig tls.Config
)
tlsConfig.InsecureSkipVerify = true 复制代码 // If we should verify the server, we need to load a trusted ca
if *flTlsVerify {
*flTls = true
certPool := x509.NewCertPool()
file, err := ioutil.ReadFile(*flCa)
if err != nil {
log.Fatalf("Couldn't read ca cert %s: %s", *flCa, err)
}
certPool.AppendCertsFromPEM(file)
tlsConfig.RootCAs = certPool
tlsConfig.InsecureSkipVerify = false
} 复制代码 // If tls is enabled, try to load and send client certificates
if *flTls || *flTlsVerify {
_, errCert := os.Stat(*flCert)
_, errKey := os.Stat(*flKey)
if errCert == nil && errKey == nil {
*flTls = true
cert, err := tls.LoadX509KeyPair(*flCert, *flKey)
if err != nil {
log.Fatalf("Couldn't load X509 key pair: %s. Key encrypted?", err)
}
tlsConfig.Certificates = []tls.Certificate{cert}
}
} 复制代码 2.3. Docker Client的创建 if *flTls || *flTlsVerify {
cli = client.NewDockerCli(os.Stdin, os.Stdout, os.Stderr, protoAddrParts[0], protoAddrParts[1], &tlsConfig)
} else {
cli = client.NewDockerCli(os.Stdin, os.Stdout, os.Stderr, protoAddrParts[0], protoAddrParts[1], nil)
} 复制代码 ./docker/api/client/cli.go func NewDockerCli(in io.ReadCloser, out, err io.Writer, proto, addr string, tlsConfig *tls.Config) *DockerCli {
var (
isTerminal = false
terminalFd uintptr
scheme = "http"
)
if tlsConfig != nil {
scheme = "https"
}
if in != nil {
if file, ok := out.(*os.File); ok {
terminalFd = file.Fd()
isTerminal = term.IsTerminal(terminalFd)
}
}
if err == nil {
err = out
}
return &DockerCli{
proto: proto,
addr: addr,
in: in,
out: out,
err: err,
isTerminal: isTerminal,
terminalFd: terminalFd,
tlsConfig: tlsConfig,
scheme: scheme,
}
} 复制代码 3. Docker命令执行 3.1. Docker Client解析请求命令 源码部分 if err := cli.Cmd(flag.Args()...); err != nil {
if sterr, ok := err.(*utils.StatusError); ok {
if sterr.Status != "" {
log.Println(sterr.Status)
}
os.Exit(sterr.StatusCode)
}
log.Fatal(err)
} 复制代码 ./docker/api/client/cli.go的Cmd函数 ： // Cmd executes the specified command
func (cli *DockerCli) Cmd(args ...string) error {
if len(args) > 0 {
method, exists := cli.getMethod(args[0])
if !exists {
fmt.Println("Error: Command not found:", args[0])
return cli.CmdHelp(args[1:]...)
}
return method(args[1:]...)
}
return cli.CmdHelp(args...)
} 复制代码 3.2. Docker Client执行请求命令 ./docker/api/client/command.go中的CmdPull函数 cmd := cli.Subcmd("pull", "NAME[:TAG]", "Pull an image or a repository from the registry") 复制代码 tag := cmd.String([]string{"#t", "#-tag"}, "", "Download tagged image in a repository") 复制代码 if err := cmd.Parse(args); err != nil {
return nil } 复制代码 if cmd.NArg() != 1 {
cmd.Usage()
return nil
} 复制代码 var (
v = url.Values{}
remote = cmd.Arg(0)
)
v.Set("fromImage", remote)
if *tag == "" {
v.Set("tag", *tag)
} 复制代码 remote, _ = parsers.ParseRepositoryTag(remote)
// Resolve the Repository name from fqn to hostname + name
hostname, _, err := registry.ResolveRepositoryName(remote)
if err != nil {
return err
} 复制代码 cli.LoadConfigFile()
// Resolve the Auth config relevant for this server
authConfig := cli.configFile.ResolveAuthConfig(hostname) 复制代码 pull := func(authConfig registry.AuthConfig) error {
buf, err := json.Marshal(authConfig)
if err != nil {
return err
}
registryAuthHeader := []string{
base64.URLEncoding.EncodeToString(buf),
}
return cli.stream("POST", "/images/create?"+v.Encode(), nil, cli.out, map[string][]string{
" X-Registry-Auth": registryAuthHeader,
})
} 复制代码 if err := pull(authConfig); err != nil {
if strings.Contains(err.Error(), "Status 401") {
fmt.Fprintln(cli.out, "\nPlease login prior to pull:")
if err := cli.CmdLogin(hostname); err != nil {
return err
}
authConfig := cli.configFile.ResolveAuthConfig(hostname)
return pull(authConfig)
}
return err
} 复制代码 4. 总结 
/2 
京ICP备2020039040号
简书网举报电话：021-34700000
提升卡
置顶卡
沉默卡
喧嚣卡
变色卡
千斤顶
显身卡
