Function drainExecSyncIO

internal/cri/server/container_execsync.go:302–329

drainExecSyncIO drains process IO with timeout after exec init process exits. By default, the child processes spawned by exec process will inherit standard io file descriptors. The shim server creates a pipe as data channel. Both exec process and its children write data into the write end of the pi

(ctx context.Context, execProcess containerd.Process, drainExecIOTimeout time.Duration, attachDone <-chan struct{})

// the write end of the pipe for a year! It doesn't make senses that CRI plugin
// should wait for it.
func drainExecSyncIO(ctx context.Context, execProcess containerd.Process, drainExecIOTimeout time.Duration, attachDone <-chan struct{}) error {
	var timerCh <-chan time.Time

	if drainExecIOTimeout != 0 {
		timer := time.NewTimer(drainExecIOTimeout)
		defer timer.Stop()

		timerCh = timer.C
	}

	select {
	case <-timerCh:
	case <-attachDone:
		log.G(ctx).Tracef("Stream pipe for exec process %q done", execProcess.ID())
		return nil
	}

	log.G(ctx).Debugf("Exec process %q exits but the io is still held by other processes. Trying to delete exec process to release io", execProcess.ID())
	_, err := execProcess.Delete(ctx, containerd.WithProcessKill)
	if err != nil {
		if !errdefs.IsNotFound(err) {
			return fmt.Errorf("failed to release exec io by deleting exec process %q: %w",
				execProcess.ID(), err)
		}
	}
	return fmt.Errorf("failed to drain exec process %q io in %s because io is still held by other processes",
		execProcess.ID(), drainExecIOTimeout)
}