Rails on Kubernetes - part 2a: The Counter App.

This is one of a series of blog posts in which I’m walking through the process of deploying a rails application to a kubernetes cluster. Part one is here, and the previous article is here

Our rails application can connect to our database. So now let’s get it to do what we want, which is to store and display a value, and increment it whenever we click a button.

Fire up a termninal, and cd into the counter directory.

First, let’s create a scaffold for our value.

rails generate scaffold value amount:integer
rails db:migrate

This creates a lot more than we actually need, but I’m more concerned about the kubernetes part than the rails part, in this tutorial, so I’m not going to worry about that (or about best practice for our rails code).

The scaffold is designed for us to manage a set of ‘value’ records, but we only really want one, so let’s make that work.

Replace everything in app/controllers/values_controller.rb with this:

class ValuesController < ApplicationController
  def index
    @value = Value.any? ? Value.first : Value.create(amount: 0)
  end

  def update
    value = Value.find params[:id]
    value.update(amount: value.amount + 1)

    redirect_to values_path
  end
end

Replace everything in app/views/values/index.html.erb with this:

<h1>
  <%= @value.amount %>
</h1>

<%= form_for @value do |f| %>
  <%= f.submit "Increment" %>
<% end %>

Now, visit http://localhost:3000/values, and you should see this:

Every time you click the button, the number should increase.

That’s all the work we’re going to do on our rails app. It’s extremely simple, but it’s enough to prove that our rails application is interacting with our database, which is all we need.

In the next part, we’ll start to prepare the application for deployment on our kubernetes cluster.