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Versions < 3 of ELBAS are no longer being maintained. I will only be maintaining the current feature-set which relies on Launch Templates and AWS SDK v3.

Capistrano ELBAS (Elastic Load Balancer & AutoScaling)

Gem Version

ELBAS was written to ease the deployment of Rails applications to AWS AutoScale groups. During your Capistrano deployment, ELBAS 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
  • Update the AutoScale group's launch template with the AMI ID
  • Delete any outdated AMIs created by previous ELBAS deployments


Add to Gemfile, then bundle:

gem 'elbas'

Add to Capfile:

require 'elbas/capistrano'


Setup AWS credentials:

set :aws_access_key, ENV['AWS_ACCESS_KEY_ID']
set :aws_secret_key, ENV['AWS_SECRET_ACCESS_KEY']
set :aws_region,     ENV['AWS_REGION']


Instead of using Capistrano's server method, use autoscale instead in deploy/<environment>.rb (replace with your environment). Provide the name of your AutoScale group instead of a hostname:

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

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

autoscale 'app-autoscale-group', user: 'apps', roles: [:app, :web]
autoscale 'worker-autoscale-group', user: 'apps', roles: [:worker]

Run cap production deploy.

As of version 3, your AWS setup must use launch templates as opposed to launch configurations. This allows ELBAS to simply create a new launch template version with the new AMI ID after a deployment. It no longer needs to update your AutoScale group or mess around with network settings, instance sizes, etc., as that information is all contained within the launch template. Failure to use a launch template will result in a Elbas::Errors::NoLaunchTemplate error.

Customizing Server Properties

You can pass a block to autoscale and return properties for any specific server. The block accepts the server and the server's index as arguments.

For example, if you want to apply the :db role to only the first server:

autoscale 'my-autoscale-group', roles: [:app, :web] do |server, i|
  { roles: [:app, :web, :db] } if i == 0

Returning nil from this block will cause the server to use the properties passed to autoscale.

Returning anything but nil will override the entire properties hash (as opposed to merging the two hashes together).

Listing Servers

You may need to SSH into your servers while debugging deployed code, and not everyone has a jumpbox on a basic AutoScaling setup. ELBAS provides a command that will list the ssh command necessary to connect to each server in any given environment:

cap production elbas:ssh

Output will be something like:

[ELBAS] Adding server:
[ELBAS] SSH commands:
[ELBAS]     1) ssh


Deploy Rails apps to AWS AutoScale groups




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