docker-cli/cli/command/container/attach.go

package container

import (
	"context"
	"errors"
	"io"

	"github.com/docker/cli/cli"
	"github.com/docker/cli/cli/command"
	"github.com/docker/cli/cli/command/completion"
	"github.com/moby/moby/api/types/container"
	"github.com/moby/moby/client"
	"github.com/moby/sys/signal"
	"github.com/sirupsen/logrus"
	"github.com/spf13/cobra"
)

// AttachOptions group options for `attach` command
type AttachOptions struct {
	NoStdin    bool
	Proxy      bool
	DetachKeys string
}

func inspectContainerAndCheckState(ctx context.Context, apiClient client.APIClient, args string) (*container.InspectResponse, error) {
	c, err := apiClient.ContainerInspect(ctx, args)
	if err != nil {
		return nil, err
	}
	if !c.State.Running {
		return nil, errors.New("cannot attach to a stopped container, start it first")
	}
	if c.State.Paused {
		return nil, errors.New("cannot attach to a paused container, unpause it first")
	}
	if c.State.Restarting {
		return nil, errors.New("cannot attach to a restarting container, wait until it is running")
	}

	return &c, nil
}

// newAttachCommand creates a new cobra.Command for `docker attach`
func newAttachCommand(dockerCLI command.Cli) *cobra.Command {
	var opts AttachOptions

	cmd := &cobra.Command{
		Use:   "attach [OPTIONS] CONTAINER",
		Short: "Attach local standard input, output, and error streams to a running container",
		Args:  cli.ExactArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			containerID := args[0]
			return RunAttach(cmd.Context(), dockerCLI, containerID, &opts)
		},
		Annotations: map[string]string{
			"aliases": "docker container attach, docker attach",
		},
		ValidArgsFunction: completion.ContainerNames(dockerCLI, false, func(ctr container.Summary) bool {
			return ctr.State != container.StatePaused
		}),
		DisableFlagsInUseLine: true,
	}

	flags := cmd.Flags()
	flags.BoolVar(&opts.NoStdin, "no-stdin", false, "Do not attach STDIN")
	flags.BoolVar(&opts.Proxy, "sig-proxy", true, "Proxy all received signals to the process")
	flags.StringVar(&opts.DetachKeys, "detach-keys", "", "Override the key sequence for detaching a container")
	return cmd
}

// RunAttach executes an `attach` command
func RunAttach(ctx context.Context, dockerCLI command.Cli, containerID string, opts *AttachOptions) error {
	apiClient := dockerCLI.Client()

	// request channel to wait for client
	waitCtx := context.WithoutCancel(ctx)
	resultC, errC := apiClient.ContainerWait(waitCtx, containerID, "")

	c, err := inspectContainerAndCheckState(ctx, apiClient, containerID)
	if err != nil {
		return err
	}

	if err := dockerCLI.In().CheckTty(!opts.NoStdin, c.Config.Tty); err != nil {
		return err
	}

	detachKeys := dockerCLI.ConfigFile().DetachKeys
	if opts.DetachKeys != "" {
		detachKeys = opts.DetachKeys
	}

	options := container.AttachOptions{
		Stream:     true,
		Stdin:      !opts.NoStdin && c.Config.OpenStdin,
		Stdout:     true,
		Stderr:     true,
		DetachKeys: detachKeys,
	}

	var in io.ReadCloser
	if options.Stdin {
		in = dockerCLI.In()
	}

	if opts.Proxy && !c.Config.Tty {
		sigc := notifyAllSignals()
		// since we're explicitly setting up signal handling here, and the daemon will
		// get notified independently of the clients ctx cancellation, we use this context
		// but without cancellation to avoid ForwardAllSignals from returning
		// before all signals are forwarded.
		bgCtx := context.WithoutCancel(ctx)
		go ForwardAllSignals(bgCtx, apiClient, containerID, sigc)
		defer signal.StopCatch(sigc)
	}

	resp, errAttach := apiClient.ContainerAttach(ctx, containerID, options)
	if errAttach != nil {
		return errAttach
	}
	defer resp.Close()

	// If use docker attach command to attach to a stop container, it will return
	// "You cannot attach to a stopped container" error, it's ok, but when
	// attach to a running container, it(docker attach) use inspect to check
	// the container's state, if it pass the state check on the client side,
	// and then the container is stopped, docker attach command still attach to
	// the container and not exit.
	//
	// Recheck the container's state to avoid attach block.
	_, err = inspectContainerAndCheckState(ctx, apiClient, containerID)
	if err != nil {
		return err
	}

	if c.Config.Tty && dockerCLI.Out().IsTerminal() {
		resizeTTY(ctx, dockerCLI, containerID)
	}

	streamer := hijackedIOStreamer{
		streams:      dockerCLI,
		inputStream:  in,
		outputStream: dockerCLI.Out(),
		errorStream:  dockerCLI.Err(),
		resp:         resp,
		tty:          c.Config.Tty,
		detachKeys:   options.DetachKeys,
	}

	// if the context was canceled, this was likely intentional and we shouldn't return an error
	if err := streamer.stream(ctx); err != nil && !errors.Is(err, context.Canceled) {
		return err
	}

	return getExitStatus(errC, resultC)
}

func getExitStatus(errC <-chan error, resultC <-chan container.WaitResponse) error {
	select {
	case result := <-resultC:
		if result.Error != nil {
			return errors.New(result.Error.Message)
		}
		if result.StatusCode != 0 {
			return cli.StatusError{StatusCode: int(result.StatusCode)}
		}
	case err := <-errC:
		return err
	}

	return nil
}

func resizeTTY(ctx context.Context, dockerCli command.Cli, containerID string) {
	height, width := dockerCli.Out().GetTtySize()
	// To handle the case where a user repeatedly attaches/detaches without resizing their
	// terminal, the only way to get the shell prompt to display for attaches 2+ is to artificially
	// resize it, then go back to normal. Without this, every attach after the first will
	// require the user to manually resize or hit enter.
	resizeTtyTo(ctx, dockerCli.Client(), containerID, height+1, width+1, false)

	// After the above resizing occurs, the call to MonitorTtySize below will handle resetting back
	// to the actual size.
	if err := MonitorTtySize(ctx, dockerCli, containerID, false); err != nil {
		logrus.Debugf("Error monitoring TTY size: %s", err)
	}
}