Configset Variables

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

Configset Predefined Variables

Normally, configsets set predefined variables in their lib/variables.rb file. Example:

app/configsets/httpd/lib/variables.rb:

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

Set Configset Variables

You can set variables in the configs/BLUEPRINT/configets folder of your project. You can set variables globally or locally. Global overrides apply to all configsets used by the blueprint. Local overrides apply to the specifically scoped configset only.

Examples:

1. configs/ec2/configsets/variables.rb - global override for all configsets used in the ec2 blueprint
2. configs/ec2/configsets/variables/httpd.rb - local override, only to the httpd configset

If both global and local variables are set, the local variable takes higher precedence and will be used. It is generally recommended to use local overrides only. Example:

configs/ec2/configsets/variables/httpd.rb

@html =<<-EOL
<h1>project variables.rb override</h1>
<p>Hello there from configs/ec2/configsets/variables/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 Configs are Ruby

Since the configs file is Ruby, you have the full power of Ruby to organize things however you wish. Example:

configs/ec2/configsets/variables/httpd.rb

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

configs/ec2/configsets/httpd/html/index.html:

<h2>My html page</h2>
<p>Hello there from configs/ec2/configsets/httpd/html/index.html</p>

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