One and Done

One and Done is the easiest way to make HTTP requests idempotent in Elixir applications.

One and Done supports the following frameworks:

• Plug (including Phoenix)

Usage

One and Done depends on having a pre-existing cache like Nebulex. This guide assumes Nebulex is already configured under MyApp.Cache.

1. Add one_and_done to your mix.exs dependencies:

def deps do
  [
    {:one_and_done, "~> 0.1.0"}
  ]
end

1. Add OneAndDone to your Plug pipeline:

defmodule MyAppWeb.Router do
  use MyAppWeb, :router

  pipeline :api do
    # Configuration options for OneAndDone are in the docs
    plug OneAndDone.Plug, cache: MyApp.Cache
  end

  # By default, all POST and PUT requests piped through :api
  # that have an Idempotency-Key header set will be cached for 24 hours.
  scope "/api", MyAppWeb do
    pipe_through :api

    resources "/users", UserController
  end
end

1. Make your requests idempotent by adding the Idempotency-Key header:

curl -X POST \
  http://localhost:4000/api/users \
  -H 'Content-Type: application/json' \
  -H 'Idempotency-Key: 123' \
  -d '{
  "email": "hello@example.com",
  "password": "password"
  }'

Repeat the request with the same Idempotency-Key header and you will get the same response without the request being processed again.