Today, we’ll learn about lono helpers. Lono helpers allow you to extend and add to the Lono DSL as a first-class citizen. This particularly makes Lono powerful because you can write methods specific to your needs.

Example

Generally, I’ve found that refactoring the resource methods into helpers makes the template clearer to understand. We’ll use the demo project from the previous post. Let’s create aec2_helper.rb to clean it up.

app/helpers/ec2_helper.rb

module Ec2Helper
  def instance(n)
    resource("Instance#{n}", "AWS::EC2::Instance",
      InstanceType: ref("InstanceType"),
      ImageId: find_in_map("AmiMap", ref("AWS::Region"), "Ami"),
      SecurityGroupIds: [get_att("SecurityGroup#{n}.GroupId")],
      UserData: base64(sub(user_data("bootstrap.sh")))
    )
  end

  def security_group(n)
    resource("SecurityGroup#{n}", "AWS::EC2::SecurityGroup",
      GroupDescription: "demo security group",
    )
  end
end

All we did was put each resource in a method. Now update demo.rb with the new helper methods.

@instance_count ||= 1 # default to 1
@instance_count.times do |i|
  n = i + 1
  instance(n)
  security_group(n)
end

Looking at the demo template, it’s clear that an instance and security group will be created.

Deploy

Let’s deploy:

lono cfn deploy demo

Here’s the CloudFormation console:

And the ec2 console:

Summary

In this post, we used helpers to clean up the template and move the resources to the ec2_helper.rb. By doing so, it makes the template quick and easy to understand. You can immediately tell that the blueprint creates an ec2 instance and security group.

Interestingly, I usually only refactor resources into helpers. I’ve found it’s helpful to keep everything else at the top-level template. This makes it easy to scan the entire template and quickly understand how everything works.

Prebuilt CloudFormation Templates

You may be interested in BoltOps Pro blueprints. Blueprints are essentially CloudFormation templates packaged up in a convenient and reusable way. The BoltOps Pro subscription gives you access to all the blueprints in the BoltOps Pro GitHub organization. Just configure, deploy, and run.

Also, if there is a blueprint you would like to see in the future. Please feel free to send us your suggestions: Pro Blueprint Suggestion.

Lono Introduction Series