Method ContainerExecStart

daemon/exec.go:162–342

ContainerExecStart starts a previously set up exec instance. The std streams are set up. If ctx is cancelled, the process is terminated.

(ctx context.Context, name string, options backend.ExecStartConfig)

// std streams are set up.
// If ctx is cancelled, the process is terminated.
func (daemon *Daemon) ContainerExecStart(ctx context.Context, name string, options backend.ExecStartConfig) (retErr error) {
	var (
		cStdin           io.ReadCloser
		cStdout, cStderr io.Writer
	)

	ec, err := daemon.getExecConfig(name)
	if err != nil {
		return err
	}

	ec.Lock()
	if ec.ExitCode != nil {
		ec.Unlock()
		return errdefs.Conflict(fmt.Errorf("exec command %s has already run", ec.ID))
	}

	if ec.Running {
		ec.Unlock()
		return errdefs.Conflict(fmt.Errorf("exec command %s is already running", ec.ID))
	}
	ec.Running = true
	ec.Unlock()

	log.G(ctx).Debugf("starting exec command %s in container %s", ec.ID, ec.Container.ID)
	daemon.LogContainerEventWithAttributes(ec.Container, events.Action(string(events.ActionExecStart)+": "+ec.Entrypoint+" "+strings.Join(ec.Args, " ")), map[string]string{
		"execID": ec.ID,
	})

	defer func() {
		if retErr != nil {
			ec.Lock()
			ec.Container.ExecCommands.Delete(ec.ID)
			ec.Running = false
			if ec.ExitCode == nil {
				// default to `126` (`EACCES`) if we fail to start
				// the exec without setting an exit code.
				exitCode := exitEaccess
				ec.ExitCode = &exitCode
			}
			if err := ec.CloseStreams(); err != nil {
				log.G(ctx).Errorf("failed to cleanup exec %s streams: %s", ec.Container.ID, err)
			}
			ec.Unlock()
		}
	}()

	if ec.OpenStdin && options.Stdin != nil {
		r, w := io.Pipe()
		go func() {
			defer func() {
				log.G(ctx).Debug("Closing buffered stdin pipe")
				_ = w.Close()
			}()
			_, _ = pools.Copy(w, options.Stdin)
		}()
		cStdin = r
	}