Configset Variables

You can define variables to be made available in your configset code.

Configset Default Variables

Normally, configsets set default variables in their vars.rb file. Example:

app/configsets/httpd/vars.rb

@html =<<-EOL
<h1>configset predefined variables</h1>
<p>Hello from app/configsets/httpd/vars.rb</p>
EOL

User Custom Configset Variables

You can set custom variables with the config/blueprints/BLUEPRINT/configsets/CONFIGSET.rb. Notice how the configset variables are scoped to both blueprint and configset. Example:

config/blueprints/ec2/configsets/vars/httpd.rb

@html =<<-EOL
<h1>project variables.rb override</h1>
<p>Hello there from config/blueprints/ec2/configsets/vars/httpd.rb</p>
EOL

DSL Variables Access

The DSL Configset is just Ruby so you access the variables directly as instance variables.

package("yum",
  httpd: []
)
file("/var/www/html/index.html",
  content: @html
)
service("sysvinit",
  httpd: {
    enabled: true,
    ensureRunning: true,
  }
)

The variable here is @html.

ERB Variables Access

For ERB Configsets, you access the variables with ERB. The configset.yml is processed as ERB before being loaded into the CloudFormation template. This allows you to use ERB to refer to variables:

Example:

AWS::CloudFormation::Init:
  config:
    packages:
      yum:
        httpd: []
    files:
      "/var/www/html/index.html":
        content: |
<%= indent(@html, 10) %>
    services:
      sysvinit:
       httpd:
        enabled: 'true'
        ensureRunning: 'true'

Note, we’re also using the indent method to align the YAML content.

Configsets are Ruby

The configs file is just Ruby actually. So you have the full power of Ruby to organize things however you wish. Example:

config/blueprints/ec2/configsets/vars/httpd.rb

@html = IO.read(File.expand_path("html/index.html", __dir__))

config/blueprints/ec2/configsets/httpd/html/index.html:

<h2>My html page</h2>
<p>Hello from config/blueprints/ec2/configsets/httpd/html/index.html</p>

Getting Started