Hello, I need to set up file download that happens dynamically at runtime. Essentially there are images stored on s3 that need to be downloaded, sorted into a folder and then sent to the clients browser as a zip file. The code for doing all this is set up and working properly. The problem I’m running into is the controller will return without waiting for all the images to download, it returns right away so only 2-5 get downloaded, for my use case there could be 100+ images that need to be downloaded. I’m not sure why the code is not running asynchronously.

If i remove the connection return at the end of the controller, then all images get downloaded as intended, but it throws an error as the controller must return a connection.

lib/router.ex

    get "/orders/:id", OrderController, :order_page
    get "/order-download/:id", OrderController, :download_order

lib/controller/order_controller.ex

  def order_page(conn, %{"id" => id}) do
    order = SnapshotManagement.get_order(id)

    render(conn, "order.html", order: order)
  end

  def download_order(conn, %{"id" => id}) do
## the image downloader function downloads all the images to a 
## folder in priv/static and returns the path to that folder
## this is working as intended so not including the code here
    path = ImageDownloader.download_images_for_order(String.to_integer(id))
    old_path = File.cwd!
    File.cd!(path)
    {:ok, filename} = :zip.create("order.zip", ['./'], [{:cwd, path}])
    File.cd!(old_path)

    send_download(conn, {:file, path <> "/" <> filename})

    File.rm_rf!(path)

    redirect(conn, to: "/order/" <> id)
  end

order.html.eex

<li class="list-group-item"><a href="/order-download/<%= @order.id %>" class="btn btn-primary btn-lg" tabindex="-1" role="button" aria-disabled="true">Download</a></li>

Any help or ideas for other setups are appreciated, thanks!