Ranged Response Flow in Phoenix/Elixir

Question

How can I implement the flow in the first answer here on Phoenix? At first I thought I had to use Conn.send_chunked and Conn.chunk but I am starting to realize I will be getting many requests instead of me sending a various responses.

Answer 1

If anybody is interested, this is my solution. Talks correctly to video players, and also handles normal files.

[range_start, range_end] = 
    if Enum.empty?(Conn.get_req_header(conn, "range")) do
      [0, file.content_length - 1]  
    else
      [rn] = Conn.get_req_header(conn, "range")

      res = Regex.run(~r/bytes=([0-9]+)-([0-9])?/, rn)
      default_end = Integer.to_string(file.content_length - 1)

      {range_start, _} = res |> Enum.at(1) |> Integer.parse
      {range_end, _} = res |> Enum.at(2, default_end) |> Integer.parse

      [range_start, range_end]
    end

    content_length = range_end - range_start + 1

    conn = conn
      |> Conn.put_resp_content_type(file.content_type)
      |> Conn.put_resp_header("content-length", Integer.to_string(content_length))
      |> Conn.put_resp_header("accept-ranges", "bytes")
      |> Conn.put_resp_header("content-disposition", ~s(inline; filename="#{file.filename}"))
      |> Conn.put_resp_header("content-range", "bytes #{range_start}-#{range_end}/#{file.content_length}")
      |> Conn.send_file(206, "#{files_path}/#{id}", range_start, content_length)

Answer 2

Thanks for posting your solution Cristian! I never would've figured this out otherwise...

For any Elixir newbies such as myself who run across this and can't quite get the above snippet to work, here's my full controller method:

def load_song(conn, params) do
  filename = List.first(params["song"])
  file_path = "priv/static/sounds/#{filename}"
  {:ok, stats} = File.stat(file_path)
  filesize = stats.size

  [range_start, range_end] =
      if Enum.empty?(Plug.Conn.get_req_header(conn, "range")) do
        [0, filesize - 1]
      else
        [rn] = Plug.Conn.get_req_header(conn, "range")

        res = Regex.run(~r/bytes=([0-9]+)-([0-9])?/, rn)
        default_end = Integer.to_string(filesize - 2)

        {range_start, _} = res |> Enum.at(1) |> Integer.parse
        {range_end, _} = res |> Enum.at(2, default_end) |> Integer.parse

        [range_start, range_end]
      end

  content_length = range_end - range_start + 2

  conn
    |> Plug.Conn.put_resp_content_type("audio/mpeg")
    |> Plug.Conn.put_resp_header("content-length", Integer.to_string(content_length))
    |> Plug.Conn.put_resp_header("accept-ranges", "bytes")
    |> Plug.Conn.put_resp_header("content-disposition", ~s(inline; filename="#{filename}"))
    |> Plug.Conn.put_resp_header("content-range", "bytes #{range_start}-#{range_end}/#{filesize}")
    |> Plug.Conn.send_file(206, file_path, range_start, content_length)
end

I've learned since about some basic Elixir features like aliasing that would've simplified this, and I'm guessing some other coding choices are a little un-idiomatic, but the above show work as a "drop in" method for your controller.

Answer 3

I have created a plug for this called plug_range, it will catch every range request and serve them. It is still a work in progress to follow the RFC, but it might comes in handy until then.

PlugRange