Swarmkit笔记（7）——exec.Executor interface

exec.Executor interface定义（位于agent/exec/executor.go）：

// Executor provides controllers for tasks.
type Executor interface {
    // Describe returns the underlying node description.
    Describe(ctx context.Context) (*api.NodeDescription, error)

    // Configure uses the node object state to propagate node
    // state to the underlying executor.
    Configure(ctx context.Context, node *api.Node) error

    // Controller provides a controller for the given task.
    Controller(t *api.Task) (Controller, error)

    // SetNetworkBootstrapKeys passes the symmetric keys from the
    // manager to the executor.
    SetNetworkBootstrapKeys([]*api.EncryptionKey) error
}

container Package实现了executor结构体（位于agent/exec/container/executor.go）：

import engineapi "github.com/docker/engine-api/client"
type executor struct {
    client engineapi.APIClient
}

里面只有一个成员：一个Docker APIClient。executor结构体实际只实现了下面两个方法：

// Describe returns the underlying node description from the docker client.
func (e *executor) Describe(ctx context.Context) (*api.NodeDescription, error) {
    info, err := e.client.Info(ctx)
    if err != nil {
        return nil, err
    }

    plugins := map[api.PluginDescription]struct{}{}
    addPlugins := func(typ string, names []string) {
        for _, name := range names {
            plugins[api.PluginDescription{
                Type: typ,
                Name: name,
            }] = struct{}{}
        }
    }

    addPlugins("Volume", info.Plugins.Volume)
    // Add builtin driver "overlay" (the only builtin multi-host driver) to
    // the plugin list by default.
    addPlugins("Network", append([]string{"overlay"}, info.Plugins.Network...))
    addPlugins("Authorization", info.Plugins.Authorization)

    pluginFields := make([]api.PluginDescription, 0, len(plugins))
    for k := range plugins {
        pluginFields = append(pluginFields, k)
    }
    sort.Sort(sortedPlugins(pluginFields))

    // parse []string labels into a map[string]string
    labels := map[string]string{}
    for _, l := range info.Labels {
        stringSlice := strings.SplitN(l, "=", 2)
        // this will take the last value in the list for a given key
        // ideally, one shouldn't assign multiple values to the same key
        if len(stringSlice) > 1 {
            labels[stringSlice[0]] = stringSlice[1]
        }
    }

    description := &api.NodeDescription{
        Hostname: info.Name,
        Platform: &api.Platform{
            Architecture: info.Architecture,
            OS:           info.OSType,
        },
        Engine: &api.EngineDescription{
            EngineVersion: info.ServerVersion,
            Labels:        labels,
            Plugins:       pluginFields,
        },
        Resources: &api.Resources{
            NanoCPUs:    int64(info.NCPU) * 1e9,
            MemoryBytes: info.MemTotal,
        },
    }

    return description, nil
}

// Controller returns a docker container controller.
func (e *executor) Controller(t *api.Task) (exec.Controller, error) {
    ctlr, err := newController(e.client, t)
    if err != nil {
        return nil, err
    }

    return ctlr, nil
}

Describe()方法返回当前Docker engine的资源配置信息，而Controller()则返回一个container.controller结构体。

        client, err := engineapi.NewClient(engineAddr, "", nil, nil)
        if err != nil {
            return err
        }

        executor := container.NewExecutor(client)

(dlv) p client
*github.com/docker/swarmkit/vendor/github.com/docker/engine-api/client.Client {
        proto: "unix",
        addr: "/var/run/docker.sock",
        basePath: "",
        transport: (unreadable interface type "*transport.apiTransport" not found for 0xc8202ecbd8: no type entry found, use 'types' for a list of valid types),
        version: "",
        customHTTPHeaders: map[string]string [],}