Function parallelOperation

cli/command/container/utils.go:52–82

(ctx context.Context, containers []string, op func(ctx context.Context, containerID string) error)

}

func parallelOperation(ctx context.Context, containers []string, op func(ctx context.Context, containerID string) error) chan error {
	if len(containers) == 0 {
		return nil
	}
	const defaultParallel int = 50
	sem := make(chan struct{}, defaultParallel)
	errChan := make(chan error)

	// make sure result is printed in correct order
	output := map[string]chan error{}
	for _, c := range containers {
		output[c] = make(chan error, 1)
	}
	go func() {
		for _, c := range containers {
			err := <-output[c]
			errChan <- err
		}
	}()

	go func() {
		for _, c := range containers {
			sem <- struct{}{} // Wait for active queue sem to drain.
			go func(container string) {
				output[container] <- op(ctx, container)
				<-sem
			}(c)
		}
	}()
	return errChan
}