Trying to save and serve dynamically created SVG

I’m generating QR codes as an SVG dynamically. The SVG is shown right away so every time a new SVG is created, I just replace the existing one. The problem I’m encountering is that even after replacing the old SVG it seems to be cached somewhere and serves the same SVG no matter what. How can I go about creating an SVG and saving it locally then serving it properly?

  def qr_code(conn, %{"id" => id}) do
    img_path = Application.app_dir(:EOS, "priv/static/images/mysvg.svg")
    user = conn.assigns.current_user |> Repo.preload(organization: :wells)
    well = App.get_well!(id)


    |> QRCode.create(:high)
    |> Result.and_then(&QRCode.Svg.save_as(&1, img_path))

    conn = put_layout(conn, false)
    render(conn, "qr_code.html", img_path: img_path)

<img src="<%= Routes.static_url(EOSWeb.Endpoint, "/images/mysvg.svg") %>">```

The browser is caching it. Two ways to ‘bust’ the cache:

  • Set a header that prevents caching, however some browsers will override this and still cache.
  • Add something to the url, like a timestamp as part of the query. :slight_smile:

Plug.Static might also be caching it somewhere too, but I doubt it, someone else would know for sure though, but at the very least the browser will be caching it by default.


If it is getting generated dynamically, why do you need to save it to a file?

If you read the docs for QRCode.Svg.to_base64 it has an example of dynamically serving the QR code to an image tag. Alternatively, you could delivery it as an inline SVG generated from QRCode.Svg.create and embed in the template. Let us know if you need some pointers for the second option. It looks like the first is directly supported by the library.