Tiny Dockerized Sinatra Service

This little thing is a template for a Sinatra microservice packed into Docker image. The biggest advantage of it is its size - around 60MB what is quite unusual for Ruby based images.

It is based on excellent article by Travis Reeder:

How to Create a Tiny Docker Image for your Ruby App

The article is a bit outdated because step 1 has changed - it's now supposed to be done with the :dev version what's described in iron/ruby image description btw. I highly recommend going through idea of iron/base, iron/ruby & iron/ruby:dev images.

I will try to explain idea behing that for lazy ones (-;

Template structure

Structure is rather common for any Sinatra or Ruby simple app in general. So we have a main service.rb which acts an entry point for our code. It looks like this:

require_relative 'bundle/bundler/setup'

require 'sinatra/base'
require 'sinatra/json'
require 'roar'

require_relative 'lib/service_api'

ServiceApi.run!

what is happening here is:

• we first load bundled gems with require_relative 'bundle/bundler/setup' line. This file is generated during bundle install and reflects gems we have in our application. If any new gem is added or removed it needs to be rebuilt.
• next we load other elements we will use: sinatra/base, sinatra/json & roar
• now we load our "worker" class which is a Sinatra::Base instance doing the dirty work
• and finally we start it with ServiceApi.run!. If you plan to change name of the worker class don't remember to adjust this place

Adding your code

soon

Building docker image

soon

Running the container

soon