Introduction

RSS stands for Really Simple Syndication. It’s a technology that allows users to subscribe to content from their favorite websites or blogs in a standardized format, in this article we will see how to configure it for a Phoenix application in the simplest way possible.

The example will be based in this blog configuration, but it would be the same if you replace the app name tr with your app name.

Configuration

First we need to accept the format, this happens in lib/tr_web.ex

  formats: [:html, :json, :xml],

As I’m using the page controller as index for the site, I decided to reuse that controller for the sitemap and rss feed, basically the plug disables the layout for that action and the action renders the template.

  plug :put_layout, false when action in [:sitemap]

  def sitemap(conn, _params) do
    posts = Blog.all_posts()

    conn
    |> put_resp_content_type("text/xml")
    |> render("index.xml", posts: posts)
  end

Before going into the template we need to add the route for it, first we add a pipeline to accept XML and then we define the routes that will serve the sitemap.

  pipeline :xml do
    plug :accepts, ["xml"]
  end

  scope "/", TrWeb do
    pipe_through :xml

    get "/index.xml", PageController, :sitemap
    get "/sitemap.xml", PageController, :sitemap
  end

The next two files are the last part of the configuration, first lib/tr_web/controllers/page_xml.ex, we set the template and a helper to show the date.

defmodule TrWeb.PageXML do
  @moduledoc """
  Module to support xml rendering
  """
  use TrWeb, :html

  embed_templates "page_xml/*"

  defp format_date(date) do
    date
    |> to_string()
  end
end

And the last part of our configuration is the template itself lib/tr_web/controllers/page_xml/index.xml.eex, this will be used to generate the list of all posts with the relevant fields.

<?xml version="1.0" encoding="utf-8"?>
<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
  <channel>
    <title>Techsquad Rocks</title>
    <link><%= ~p"/blog" %></link>
    <atom:link href="<%= ~p"/index.xml" %>" rel="self" type="application/rss+xml" />
    <description>This blog was created to document and learn about different technologies, among other things it has
    been deployed to a k3s cluster running in OCI, using elixir and the phoenix framework, postgres, docker, kubernetes
    on ARM64, and many other things, if that sounds interesting, you can follow me on twitter or create an account here
    to receive new posts notifications and later on a newsletter, so I hope you enjoy your stay and see you on the other
    side...</description>
    <language>en</language>
    <copyright>Copyright <%= DateTime.utc_now.year %> TechSquad Rocks </copyright>
    <lastBuildDate><%= DateTime.utc_now |> format_date() %></lastBuildDate>
    <category>IT/Internet/Web development</category>
    <ttl>60</ttl>

    <%= for post <- @posts do %>
      <item>
        <title><%= post.title %></title>
        <link><%= ~p"/blog/#{post.id}" %></link>
        <guid><%= ~p"/blog/#{post.id}" %></guid>
        <description><![CDATA[ <%= post.description %> ]]></description>
        <pubDate><%= post.date |> format_date %></pubDate>
        <source url="<%= ~p"/blog" %>">Blog Title</source>
      </item>
    <% end %>
  </channel>
</rss>

You can also test it this way, remember that if you decide to use another module you will have to place that there instead of where the page controller tests are:

  describe "GET /sitemap.xml" do
    test "accesses the sitemap in format xml", %{conn: conn} do
      conn = get(conn, "/sitemap.xml")

      assert response_content_type(conn, :xml)
      assert response(conn, 200) =~ "<link>/blog/from_zero_to_hero_with_kops_and_aws</link>"
    end
  end

Then you can provide your readers with a link like this one so your readers can discover your feed:

<.link rel="alternate" type="application/rss+xml" title="Blog Title" href={~p"/index.xml"}>
  RSS
</.link>

Closing notes

Let me know if there is anything that you would like to see implemented or tested, explored and what not in here…

Errata

If you spot any error or have any suggestion, please send me a message so it gets fixed.

Also, you can check the source code and changes in the sources here