Swarmkit筆記（7）——exec.Executor interface

這是一個建立於 的文章，其中的資訊可能已經有所發展或是發生改變。

exec.Executor interface定義（位於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實現了executor結構體（位於agent/exec/container/executor.go）：

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

裡面只有一個成員：一個Docker APIClient。executor結構體實際只實現了下面兩個方法：

// 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()方法返回當前Docker engine的資源配置資訊，而Controller()則返回一個container.controller結構體。

其中關於client的初始化位於：

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

如果沒有對engineAddr做特殊設定，就會使用其預設值：unix:///var/run/docker.sock。client值預設如下：

(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 [],}