Capistrano::Decompose

Add tasks for capistrano to deploy with docker-compose.

Why?

when I was working on my project Who is popular today I had that problem that I have a VPS server and I need to isolate each of my apps to a separate environment so the solutions are pretty limited in here, it's Docker or LXC, I choose Docker and Docker-Compose as it's easier to get a set of disposable environments up and running in no time and link them to the host data directories which is what I needed, but there where not any kind of integeration with Capistrano to roll out new versions, so here is Capistrano-Decompose a Docker-Compose integeration with capistrano, I hope it solves your problem as it did to mine.

How it works

After capistrano pull your repo and link it to the current directory, decompose will invoke docker-compose build to build your images and then run some rake tasks that you configured in your deployment with the key decompose_rake_tasks, you can add your rails tasks like db:migration, assets:precompile...etc here, then it will invoke docker-compose up or restart only the web service you specified in key decompose_restart, also you can use cap <env> decompose:run to run any command inside a service, so anytime you need to invoke rails console inside you docker image on your server you can use cap production decompose:run rails console.

At the end decompose will delete the older images from remote server to keep the server clean.

Installation

Add this line to your Gemfile

gem 'capistrano-decompose'

And then execute:

$ bundle

Or install it yourself as:

$ gem install capistrano-decompose

Usage

Add this line to your Capfile:

require 'capistrano/decompose

Options for deployment

You can specify the following options in you deploy.rb script or the environment specific deploy file:

• decompose_restart: An array of services that should be restarted each deployment, if not specified decompose will restart all services
• decompose_web_service: The web service that will be used to execute commands inside like rake or any interactive command from decompose:run, default value: :web
• decompose_rake_tasks: An array of rake tasks to execute after each deploy on the web_service or a Hash of service_name => [task1, task2...], default value is nil

For a typical rails application the previous options should be as follows, given that the application container service name is web:

set :decompose_restart, [:web]
set :decompose_web_service, :web
set :decompose_rake_tasks, ['db:migrate', 'assets:precompile']
set :compose_file, "docker-compose file name"

Defined Tasks

decompose:build                # build docker-compose services
decompose:clean                # delete docker images that are not related to current build
decompose:down                 # shutdown all project services with docker-compose
decompose:rake_tasks           # execute a set of rake tasts inside the web container
decompose:restart              # restart services of docker-compose and if not services listed restart all services
decompose:run                  # run an interactive command inside the web container
decompose:up                   # boot up all docker-compose services

After the first deployment of a rails application

You would need to setup your database by invoking the db:setup task to create and seed your database:

• cap production decompose:run rake db:setup

General note

• This gem doesn't provide a dockerfile nor docker-compose.yml file, you have to create these files yourself
• The linked directories and files will not work and you should use docker data volumes anyway