docker笔记（14）——docker swarm功能代码分析（1）

Docker 1.12集成了docker swarm功能，其client的相关代码位于api/client/swarm文件夹下。以docker swarm init命令的代码（api/client/swarm/init.go）为例：

const (
    generatedSecretEntropyBytes = 16
    generatedSecretBase         = 36
    // floor(log(2^128-1, 36)) + 1
    maxGeneratedSecretLength = 25
)

type initOptions struct {
    swarmOptions
    listenAddr NodeAddrOption
    // Not a NodeAddrOption because it has no default port.
    advertiseAddr   string
    forceNewCluster bool
}

func newInitCommand(dockerCli *client.DockerCli) *cobra.Command {
    opts := initOptions{
        listenAddr: NewListenAddrOption(),
    }

    cmd := &cobra.Command{
        Use:   "init [OPTIONS]",
        Short: "Initialize a swarm",
        Args:  cli.NoArgs,
        RunE: func(cmd *cobra.Command, args []string) error {
            return runInit(dockerCli, cmd.Flags(), opts)
        },
    }

    flags := cmd.Flags()
    flags.Var(&opts.listenAddr, flagListenAddr, "Listen address (format: <ip|interface>[:port])")
    flags.StringVar(&opts.advertiseAddr, flagAdvertiseAddr, "", "Advertised address (format: <ip|interface>[:port])")
    flags.BoolVar(&opts.forceNewCluster, "force-new-cluster", false, "Force create a new cluster from current state.")
    addSwarmFlags(flags, &opts.swarmOptions)
    return cmd
}

func runInit(dockerCli *client.DockerCli, flags *pflag.FlagSet, opts initOptions) error {
    client := dockerCli.Client()
    ctx := context.Background()

    req := swarm.InitRequest{
        ListenAddr:      opts.listenAddr.String(),
        AdvertiseAddr:   opts.advertiseAddr,
        ForceNewCluster: opts.forceNewCluster,
        Spec:            opts.swarmOptions.ToSpec(),
    }

    nodeID, err := client.SwarmInit(ctx, req)
    if err != nil {
        if strings.Contains(err.Error(), "could not choose an IP address to advertise") || strings.Contains(err.Error(), "could not find the system's IP address") {
            return errors.New(err.Error() + " - specify one with --advertise-addr")
        }
        return err
    }

    fmt.Fprintf(dockerCli.Out(), "Swarm initialized: current node (%s) is now a manager.\n\n", nodeID)

    if err := printJoinCommand(ctx, dockerCli, nodeID, true, false); err != nil {
        return err
    }

    fmt.Fprint(dockerCli.Out(), "To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.\n\n")
    return nil
}

其中client.DockerCli代表docker command line client：

// DockerCli represents the docker command line client.
// Instances of the client can be returned from NewDockerCli.
type DockerCli struct {
    // initializing closure
    init func() error

    // configFile has the client configuration file
    configFile *configfile.ConfigFile
    // in holds the input stream and closer (io.ReadCloser) for the client.
    in io.ReadCloser
    // out holds the output stream (io.Writer) for the client.
    out io.Writer
    // err holds the error stream (io.Writer) for the client.
    err io.Writer
    // keyFile holds the key file as a string.
    keyFile string
    // inFd holds the file descriptor of the client's STDIN (if valid).
    inFd uintptr
    // outFd holds file descriptor of the client's STDOUT (if valid).
    outFd uintptr
    // isTerminalIn indicates whether the client's STDIN is a TTY
    isTerminalIn bool
    // isTerminalOut indicates whether the client's STDOUT is a TTY
    isTerminalOut bool
    // client is the http client that performs all API operations
    client client.APIClient
    // state holds the terminal input state
    inState *term.State
    // outState holds the terminal output state
    outState *term.State
}

其中的client成员便是engine-api/client，所以上述client.SwarmInit的代码位于engine-api/client/swarm_init.go：

// SwarmInit initializes the Swarm.
func (cli *Client) SwarmInit(ctx context.Context, req swarm.InitRequest) (string, error) {
    serverResp, err := cli.post(ctx, "/swarm/init", nil, req, nil)
    if err != nil {
        return "", err
    }

    var response string
    err = json.NewDecoder(serverResp.body).Decode(&response)
    ensureReaderClosed(serverResp)
    return response, err
}