僅供自己梳理了解最新代碼流程，有些細節並不會展開深挖
1、進入客戶端接收代碼塊，由runInfo方法返回內容
github.com/docker/cli/cli/command/system/info.go

// NewInfoCommand creates a new cobra.Command for `docker info`
func NewInfoCommand(dockerCli command.Cli) *cobra.Command {
    var opts infoOptions

    cmd := &cobra.Command{
        Use:   "info [OPTIONS]",
        Short: "Display system-wide information",
        Args:  cli.NoArgs,
        RunE: func(cmd *cobra.Command, args []string) error {
            return runInfo(dockerCli, &opts)
        },
    }

func runInfo(dockerCli command.Cli, opts *infoOptions) error {
    ctx := context.Background()
    info, err := dockerCli.Client().Info(ctx)   
 

2、 請求轉發給docker daemon處理
github.com/docker/cli/vendor/github.com/docker/docker/client/info.go

// Info returns information about the docker server.
func (cli *Client) Info(ctx context.Context) (types.Info, error) {
    var info types.Info
    serverResp, err := cli.get(ctx, "/info", url.Values{}, nil)

3、docker daemon的監聽路由，進入到SystemInfo處理

// NewRouter initializes a new system router
func NewRouter(b Backend, c ClusterBackend, fscache *fscache.FSCache, builder *buildkit.Builder, features *map[string]bool) router.Router {
   router.NewGetRoute("/info", r.getInfo),  

github.com/docker/docker/api/server/router/system/system_routes.go

func (s *systemRouter) getInfo(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
    info, err := s.backend.SystemInfo()

4、經過進入systemInfo處理方法，可知container狀態信息是已經在內存中數據
github.com/docker/docker/daemon/info.go

// SystemInfo returns information about the host server the daemon is running on.
func (daemon *Daemon) SystemInfo() (*types.Info, error) {
    sysInfo := sysinfo.New(true)
    cRunning, cPaused, cStopped := stateCtr.get()

    v := &types.Info{
        ID:                 daemon.ID,
        Containers:         cRunning + cPaused + cStopped,
        ContainersRunning:  cRunning,
        ContainersPaused:   cPaused,
        ContainersStopped:  cStopped,   

5、找到設置container運行狀態的數據方法
github.com/docker/docker/daemon/metrics.go

func (ctr *stateCounter) set(id, label string) {
    ctr.mu.Lock()
    ctr.states[id] = label
    ctr.mu.Unlock()
}       

6、容器狀態數據來源
6.1、順著設置方法找到在創建container時會設置一條數據，這是初始化的數據
github.com/docker/docker/daemon/create.go

// Create creates a new container from the given configuration with a given name.
func (daemon *Daemon) create(params types.ContainerCreateConfig, managed bool) (retC *container.Container, retErr error) {
   stateCtr.set(container.ID, "stopped")

6.2、容器操作（暫停、啟動、恢復）
github.com/docker/docker/daemon/pause.go

// containerPause pauses the container execution without stopping the process.
// The execution can be resumed by calling containerUnpause.
func (daemon *Daemon) containerPause(container *container.Container) error {
    container.Paused = true
    daemon.setStateCounter(container)

github.com/docker/docker/daemon/start.go

// containerStart prepares the container to run by setting up everything the
// container needs, such as storage and networking, as well as links
// between containers. The container is left waiting for a signal to
// begin running.
func (daemon *Daemon) containerStart(container *container.Container, checkpoint string, checkpointDir string, resetRestartManager bool) (err error) {
    container.SetRunning(pid, true)
    container.HasBeenManuallyStopped = false
    container.HasBeenStartedBefore = true
    daemon.setStateCounter(container)

github.com/docker/docker/daemon/unpause.go

// containerUnpause resumes the container execution after the container is paused.
func (daemon *Daemon) containerUnpause(container *container.Container) error {
    container.Paused = false
    daemon.setStateCounter(container)    

6.3、docker重啟後，從目錄中獲取容器狀態
github.com/docker/docker/daemon/daemon.go

func (daemon *Daemon) restore() error {
   for _, c := range containers {
     //從文件config.v2.json中獲取容器狀態
     daemon.setStateCounter(c)

     //如文件中的狀態是運行或暫停，再進行檢查，並重置狀態
     if c.IsRunning() || c.IsPaused() {
     default:
                            // running
                            c.Lock()
                            c.Paused = false
                            daemon.setStateCounter(c)

7、事件變更重置容器狀態（windows)
7.1、container狀態變更的信息方法
github.com/docker/docker/daemon/monitor.go

func (daemon *Daemon) setStateCounter(c *container.Container) {
    switch c.StateString() {
    case "paused":
        stateCtr.set(c.ID, "paused")
    case "running":
        stateCtr.set(c.ID, "running")
    default:
        stateCtr.set(c.ID, "stopped")
    }
}   

7.2、windows事件監聽
github.com/docker/docker/daemon/monitor.go

// ProcessEvent is called by libcontainerd whenever an event occurs
func (daemon *Daemon) ProcessEvent(id string, e libcontainerd.EventType, ei libcontainerd.EventInfo) error {
    case libcontainerd.EventExit:
       daemon.setStateCounter(c)
    case libcontainerd.EventStart:

        // This is here to handle start not generated by docker
        if !c.Running {
            c.SetRunning(int(ei.Pid), false)
            c.HasBeenManuallyStopped = false
            c.HasBeenStartedBefore = true
            daemon.setStateCounter(c)

    case libcontainerd.EventPaused:

        if !c.Paused {
            c.Paused = true
            daemon.setStateCounter(c)

    case libcontainerd.EventResumed:
        if c.Paused {
            c.Paused = false
            daemon.setStateCounter(c)   

8、開啟啟動docker時的debug模式，獲取文件描述、goroute等信息
dockerd --debug
github.com/docker/cli/cli/command/system/info.go

if info.Debug {
        fmt.Fprintln(dockerCli.Out(), " File Descriptors:", info.NFd)
        fmt.Fprintln(dockerCli.Out(), " Goroutines:", info.NGoroutines)
        fmt.Fprintln(dockerCli.Out(), " System Time:", info.SystemTime)
        fmt.Fprintln(dockerCli.Out(), " EventsListeners:", info.NEventsListener)
    }

docker v18.09.4-rc1系列源碼解讀之docker info 命令請求流程