Output to a string instead of STDOUT?

[ianneub]

Output to a string instead of STDOUT?

[howech]

This is an excellent suggestion, and I will get on it when I get some time - maybe by the weekend.

If you want to take a crack at it, look at the way lib/cfndsl.rb works. Basically, it sets up the CloudFormation function to create a CloudFormationTemplate, evaluate the block given in its context, run a few tests and the it calls "generateOutput".

generateOutput is stupid - it just calls to_json and prints the result to stdout.

You could write your own version of the CloudFormation function found in lib/cfndsl.rb that does all of the same things, except that instead of calling x.generateOutput it returns x.to_json.

[ianneub]

I gave it a shot and was able to get it working from irb, but not through Rails.

Here is my tiny patch: ianneub@f372496

From irb I do the following:

require './lib/cfndsl'

test =<<-END
Description "asdasdff"

Parameter "AppType" do
  Description "Name of the application type run. Either: abc or def"
  Type "String"
  Default "abc"
  AllowedValues ["abc", "def"]
end
END

CloudFormation do
  eval(test)
end

This is the output:

{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Description": "asdasdff",
    "Parameters": {
        "AppType": {
            "Type": "String",
            "Description": "Name of the application type run. Either: abc or def",
            "Default": "abc",
            "AllowedValues": [
                "abc",
                "def"
            ]
        }
    }
}

Perfect!

However, from rails I get this:

{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Description": "asdasdff",
    "Parameters": {
        "AppType": "abc"
    }
}

Here is my model:

class CloudFormation < ActiveRecord::Base
  def to_json
    begin
      the_code = self.code
      CloudFormation do
        eval(the_code)
      end
    rescue => e
      "#{e.class} - #{e.message} - #{e.backtrace.join("\n")}"
    end
  end
end

Not sure why it's not working through the blocks inside the eval from rails.

Any thoughts?

[ianneub]

This isn't an ideal solution, but it's what I finally got working...

Instead of running the CloudFormation function in the Rails process I spawn a new process using Open3.

This has the benefit of being isolated from the Rails env so that cfndsl doesn't conflict with Rails and also so that I can eval user generated code in a safer env.

Here's how I did it:

Created a new file in the root of my rails project that accepts the cfndsl code to run over STDIN and outputs it back to STDOUT:

require 'cfndsl'

x = CfnDsl::CloudFormationTemplate.new
x.instance_eval STDIN.read
puts x.to_json

In my model I use this code to execute the process:

my_code_string = "Description 'asdf'"

stdin, stdout, stderr, wait_thr = Open3.popen3("ruby #{Rails.root}/cfndsl.rb")
stdin.write(my_code_string)
stdin.close
if wait_thr.value.exitstatus == 0
  stdout.read
else
  stderr.read
end