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capistrano-asg

This is a fork of lserman/capistrano-elbas, updated with new features and Capistrano 3 conventions.

capistrano-asg was written to ease the deployment of Rails applications to AWS AutoScale groups. capistrano-asg will:

  • Deploy your code to each running instance connected to a given AutoScale group
  • After deployment, create an AMI from one of the running instances
  • Attach the AMI with the new code to a new AWS Launch Configuration
  • Update your AutoScale group to use the new launch configuration
  • Delete any old AMIs created by capistrano-asg
  • Delete any old launch configurations created by capistrano-asg

This ensures that your current and future servers will be running the newly deployed code.

Installation

gem 'capistrano-asg'

Add this statement to your Capfile:

require 'capistrano/asg'

Configuration

Below are the Capistrano configuration options with their defaults:

set :aws_access_key_id,     ENV['AWS_ACCESS_KEY_ID']
set :aws_secret_access_key, ENV['AWS_SECRET_ACCESS_KEY']
set :aws_region,            ENV['AWS_REGION']

# To set region specific things:
set "#{ENV['AWS_REGION']}_#{asg}".to_sym, {
  aws_no_reboot_on_create_ami: true,
  aws_autoscale_instance_size: 'm1.small',
  aws_launch_configuration_detailed_instance_monitoring: true,
  aws_launch_configuration_associate_public_ip: true
}

where asg is the name of the autoscaling group in the given region.

Usage

Instead of using Capistrano's server method, use autoscale instead in deploy/production.rb (or whichever environment you're deploying to). Provide the name of your AutoScale group instead of a hostname:

autoscale 'production', user: 'apps', roles: [:app, :web, :db]

If you have multiple autoscaling groups to deploy to, specify each of them:

autoscale 'asg-app', user: 'apps', roles: [:app, :web]
autoscale 'asg-db', user: 'apps', roles: [:db]

Similarly, if you are deploying to multiple regions and/or multiple ASGs:

asgs    = %w(asg1 asg2)
regions = %w(us-east-1 eu-west-1)

asgs.each do |asg|
  regions.each do |region|
    set :aws_region, region
    set "#{region}_#{asg}".to_sym, {
      aws_autoscale_instance_size: 't2.medium'
      ...
    }
    autoscale asg, user: 'apps', roles: [:app, :web, :db]
  end
end

The name of the newly created launch configurations are available via fetch(:asg_launch_config). This is a two-dimensional hash with region and autoscaling group name as keys. You can output these or store them as necessary in an after 'deploy:finished' hook. An example value is:

{
  'us-east-1' => {
    'asg-app' => 'cap-asg-production-app-server-private-asg-lc-1501619456'
  },
  'eu-west-1' => {
    'asg-app' => 'cap-asg-production-app-server-private-asg-lc-1501619454'
  }
}

That's it! Run cap production deploy. The following log statements are printed during deployment:

Autoscaling: Adding server: ec2-XX-XX-XX-XXX.compute-1.amazonaws.com
Autoscaling: Creating EC2 AMI from i-123abcd
Autoscaling: Created AMI: ami-123456
Autoscaling: Creating an EC2 Launch Configuration for AMI: ami-123456
Autoscaling: Created Launch Configuration: cap-asg-lc-ENVIRONMENT-UNIX_TIMESTAMP
Autoscaling: Attaching Launch Configuration to AutoScale Group
Autoscaling: Deleting old launch configuration: cap-asg-lc-production-123456
Autoscaling: Deleting old image: ami-999999