Hi Everyone,

I have controller that takes request with a CSV file & email_id in the parameter.
What is does each read through each line of the CSV file and process the data and insert into the DB and returns the processed data for each line from the DB.

I add this processed data into a list and dump it as iodata into CSV binary and send that CSV file as an attachment using :bamboo library.

The problem I am facing is as the size of the file grows the request is taking time to process so I want to do it asynchronously.

Like I get /process data request and then send response as it is being processed to the client and do the job in the backend and send the mail on completion of the job.

Below is the snippet of my code.

def call(csv_path, email) do
    csv_path
      |> read_csv
      |> dump_to_csv
      |> add_attachment
      |> Email.create(email)
      |> Email.send_email
      |> form_response
  end

  def read_csv(csv_path) do
      csv_path
        |> File.stream!
        |> MyParser.parse_stream
        |> Stream.map(fn [arg1, arg2] -> %{prefix: arg1, url: arg2} end)
        |> Enum.flat_map(fn(params) -> url_convertor(params) end)
  end

  def url_convertor(%{url: url, prefix: prefix}) do
    with {:ok, %Route{} = route} <- MyApp.process_data(%{"prefix" => prefix, "url" => url}) do
      route
        |> MyApp.processed_data
        |> add_to_list(route, prefix)
    else
      {:error, %{changes: changes, errors: _}} -> [[prefix, changes[:url], "INVALID_URL"]] 
    end
  end

  def add_to_list(new_url, %{url: original_url}, prefix) do
    [[prefix, original_url, new_url] | []]
  end

  def dump_to_csv(list) do
    [["PREFIX", "ORIGINAL_URL", "NEW_URL"]] ++ list
      |> MyParser.dump_to_iodata()
      |> IO.iodata_to_binary
  end

  def add_attachment(binary_data) do
    %Bamboo.Attachment{content_type: "text/csv", filename: "data.csv", data: binary_data}
  end

Library Used:

:nimble_csv, bamboo_smtp

Can you help me how to make this process async.