kryptek/capistrano-ec2tag

Introduction

capistrano-ec2tag is a Capistrano plugin designed to simplify the task of deploying to infrastructure hosted on Amazon EC2. It was completely inspired by the capistrano-ec2group plugin, to which all credit is due.

While the original capistrano-ec2group plugin served me well, I started to run into limitations pretty quickly. I will say that at the time that the capistrano-ec2group plugin was written, I don't think Amazon EC2 supported tags.

Using Tags instead of Security Groups gives you the ability to change which servers get deployed to at any time, without having to reboot the instance. This implementation is particularly useful for A/B deployments, or in auto-scaling environments.

Installation

Set the Amazon AWS Credentials

In order for the plugin to list out the hostnames of your EC2 instances, it will need access to the Amazon EC2 API. Specify the following in your Capistrano configuration:

set :aws_access_key_id, '...'
set :aws_secret_access_key, '...'

Suggestion

My prefferred method of passing Amazon AWS credentials to the different tools is to use environment variables. A trick I picked up from the Chef help site.

In my ~/.zshrc I have:

# Set the Amazon AWS credentials as environment variables
export AWS_ACCESS_KEY_ID='...'
export AWS_SECRET_ACCESS_KEY='...'

Then, in a ~/.caprc I do the following:

set :aws_access_key_id, $AWS_ACCESS_KEY_ID
set :aws_secret_access_key, $AWS_SECRET_ACCESS_KEY

Get the gem

The plugin is distributed as a Ruby gem.

Ruby Gems

gem install capistrano-ec2tag

Bundler

Using bundler?

gem install bundler

Then add the following to your Gemfile:

source 'http://rubygems.org'
gem 'capistrano-ec2tag'

Install the gems in your manifest using:

bundle install

Usage

Tag your instances

Using the Amazon EC2 API or the AWS Management Console, add a deploy tag to all the instances you want Capistrano to deploy to.

The value can be any string, but I do recommend it be both unique and easy to recognize. If you have used the capistrano-ec2group, then this might be equal to whatever security group names you use.

Personally, we use the folowing convention:

ENVIRONMENT-APP-STACK

Configure Capistrano

require 'capistrano/ec2tag'

task :production do
  tag 'production-github-web', :web
  tag 'production-github-job', :job
  logger.info 'Deploying to the PRODUCTION environment!'
end

task :staging do
  tag 'staging-github-web', :web
  tag 'staging-github-job', :job
  logger.info 'Deploying to the STAGING environment!'
end

kryptek / capistrano-ec2tag