Duplicate emails been sent from Heroku deployed Phoenix App

Question

Thank you for your help. I'm new to development and Phoenix.

Recently I developed a website that sends an email when the form is submitted.

I tested the application in the iex enviroment and works just fine, it sends just one email with the information from the form. But when I deploy the application to Heroku, the email gets sent twice and I can't figure out why.

I am using SMTP with Bamboo dependencies in my mix.exs file, and I am using Bluehost SMTP configuration.

Here's what the code looks like:

mix.exs

defp deps do
[
  {:phoenix, "~> 1.3.2"},
  {:phoenix_pubsub, "~> 1.0"},
  {:phoenix_ecto, "~> 3.2"},
  {:postgrex, ">= 0.0.0"},
  {:phoenix_html, "~> 2.10"},
  {:phoenix_live_reload, "~> 1.0", only: :dev},
  {:gettext, "~> 0.11"},
  {:bamboo, "~> 1.0"},
  {:cowboy, "~> 1.0"},
  {:bamboo_smtp, "~> 1.5.0"}
]
end

config.exs

config :app, App.Mailer,                                                                                                                                                                         
  adapter: Bamboo.SMTPAdapter,                                                                                                                                                                                
  server: "mail.app.com",                                                                                                                                                                                   
  hostname: "app.com",                                                                                                                                                                                      
  port: 26,
  username: System.get_env("USER_ID"),
  password: System.get_env("USER_PASS"),
  tls: :if_available,
  allowed_tls_versions: [:"tlsv1", :"tlsv1.1", :"tlsv1.2"],
  ssl: false,
  retries: 1,
  no_mx_lookups: false,
  auth: :always

email.ex

defmodule App.Email do
  use Bamboo.Phoenix, view: App.EmailView

def contact_email(message) do
  new_email()
  |> from("postmaster@app.com")
  |> to("contacto@app.com")
  |> put_text_layout({AppWeb.LayoutView, "email.html"})
  |> subject("New lead in App")
  |> assign(:message, message)
  |> render("send_email.html")
  |> App.Mailer.deliver_later
end

mailer.exs

defmodule App.Mailer do
  use Bamboo.Mailer, otp_app: :app
end

Also, in my .gitignore file I'm ignoring my .env file that contains my environment variables, and I already set them in Heroku with:

heroku config:set VARIABLE_NAME=variable

I have no idea what could be happening and appreciate all the answers I can get. Also, if you need further information of the code, let me know.

Answer 1

This is just a guess, but you are probably calling App.Mailer.deliver_later (or App.Mailer.deliver_now) multiple times. Once from App.Email.contact_email and once from the controller action that receives the posted form data.

If that is the case, removing App.Mailer.deliver_later from the contact_email function is probably the solution.