Class: CfnPP::Replacer

Inherits:
Object
  • Object
show all
Defined in:
lib/cfnpp/replacer.rb

Overview

Implements logic for having textual templates that get turned into CloudFormation Fn::Join invocations. This makes userdata scripts and other things much easier to read.

The templates are ERB syntax, with three functions available for inserting CloudFormation references: cfn_raw, cfn_ref and cfn_getatt.

Example Template

#!/bin/bash
yum update -y aws-cfn-bootstrap
/opt/aws/bin/cfn-init -s <%= cfn_ref("AWS::StackId") %> -r LaunchConfig --region <%= cfn_ref("AWS::Region") %>
/opt/aws/bin/cfn-signal -e $? <%= cfn_ref("WaitHandle") %>
# Setup correct file ownership
chown -R apache:apache /var/www/html/wordpress

Example use of CfnPP::Replacer

template_text = "..."
cfn_hash = CfnReplacer.new.process(template_text)

Instance Method Summary collapse

Constructor Details

#initialize(text, vars = {}, opts = {}) ⇒ Replacer

Turns input text into a Hash appropriate for inserting into a CloudFormation structure.



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# File 'lib/cfnpp/replacer.rb', line 28

def initialize(text, vars = {}, opts = {})
  @text = text
  @r_vars = vars
  @opts = opts
end

Instance Method Details

#cfn_cfnpp_ref(s) ⇒ Object

for local refs (instead of cfn_ref)



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# File 'lib/cfnpp/replacer.rb', line 58

def cfn_cfnpp_ref(s)
  return @opts[s]
end

#cfn_getatt(k, v) ⇒ Object

shortcut for inserting a cfn “Fn::GetAtt”; just pass a two element array of the key and value to get



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# File 'lib/cfnpp/replacer.rb', line 75

def cfn_getatt(k,v)
	return cfn_raw({ "Fn::GetAtt" => [k, v]})
end

#cfn_raw(h) ⇒ Object

called in the template to include any arbitrary CloudFormation code.



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# File 'lib/cfnpp/replacer.rb', line 63

def cfn_raw(h)
	txt = JSON.dump h
	return "@@@#{txt}@@@"
end

#cfn_ref(s) ⇒ Object

shortcut for inserting a cfn “Ref”; just pass the “Ref” value



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# File 'lib/cfnpp/replacer.rb', line 69

def cfn_ref(s)
	return cfn_raw({ "Ref" => s })
end

#cfn_render(path) ⇒ Object 



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# File 'lib/cfnpp/replacer.rb', line 51

def cfn_render(path)
			txt = File.read File.join(File.dirname('.'), path)
			tmpl = ERB.new txt
			return tmpl.result(self.get_binding)
end

#get_binding ⇒ Object 



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# File 'lib/cfnpp/replacer.rb', line 79

def get_binding
	binding
end

#process ⇒ Object 



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# File 'lib/cfnpp/replacer.rb', line 34

def process()
	tmpl = ERB.new @text
	joinparts = []
	tmpl.result(self.get_binding).split('@@@').each do |chunk|
		if chunk.match(/^\{/)
			chunk = JSON.parse(chunk)
		end
		joinparts.push(chunk)
	end
	return { "Fn::Join" => [ '', joinparts ] }
end

#process_basic ⇒ Object 



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# File 'lib/cfnpp/replacer.rb', line 46

def process_basic()
  tmpl = ERB.new @text
  return tmpl.result(self.get_binding)
end