Generating a Packer template from Scala using the Play Framework JSON library to allow annotations as comments.

ServerMill

package io.point.servermill

import play.api.libs.json.Json
import java.io.File

object ServerMill extends App {

  // generate a Packer template to build an AMI for a
  // server instance on AWS.
  //
  // Some of this is cribbed from https://github.com/micmro/Vagrant-play
  //
  // I learned a lot about chef-solo by messing
  // with https://github.com/SegFaultx64/vagrant-play
  // but may well not use it any time soon
  //
  // My main motivation for generating packer templates out of Scala was
  // to make it possible to annotate the template (you can't put comments in JSON; who knew?)
  // but other benefits may emerge.
  // (Including having the ability to generate different templates
  // and have them backed up in the project repo.)
  // This also documents our external environmental dependencies.

  // to use: In the Play console...

  //[pointflow] $ run-main io.point.servermill.ServerMill target/packerTemplate
  //[info] Updating {file:/C:/Users/maggie/Documents/point.io/workflow/}pointflow...
  //[info] Done updating.
  //[info] Compiling 2 Scala sources to C:\Users\maggie\Documents\point.io\workflow\target\scala-2.10\classes...
  //[warn] there were 1 feature warnings; re-run with -feature for details
  //[warn] one warning found
  //[info] Running io.point.servermill.ServerMill target/packerTemplate
  //Packer template written to target/packerTemplate
  //[success] Total time: 43 s, completed Feb 3, 2014 8:56:04 AM


  val packerTemplate = Json.obj(

    // these AWS credentials are set on the Packer command line
    // and picked up in the amazon-ebs builder thus:
    // packer build -var 'aws_access_key=XXXXXXXXXXXXXXXXXX' -var 'aws_secret_key=XXXXXXXXXXXXXXXXXXX' packerTemplate

    "variables" -> Json.obj("aws_access_key" -> "", "aws_secret_key" -> ""),

    "builders" -> Json.arr(

      Json.obj(

        // http://www.packer.io/docs/builders/amazon.html
        "type" -> "amazon-ebs",

        // provide AWS user creds to provisioner
        "access_key" -> "{{user `aws_access_key`}}",
        "secret_key" -> "{{user `aws_secret_key`}}",

        // https://help.ubuntu.com/community/EC2StartersGuide
        // http://cloud-images.ubuntu.com/releases/12.04.2/release-20130222/
        // ami-de0d9eb7 us-east-1 64-bit ebs Ubuntu 12.04.2 LTS (Precise Pangolin)
        "region" -> "us-east-1",
        "source_ami" -> "ami-de0d9eb7",

        "instance_type" -> "t1.micro",
        "ssh_username" -> "ubuntu",
        "ami_name" -> "PointflowServer {{timestamp}}"
      )

    ),

    // provisioners: inject software packages needed by the app into the server image
    "provisioners" -> Json.arr(

      Json.obj(
        "type" -> "shell",
        "inline" -> Json.arr(
          "sleep 30", // allow time for the EC2 instance under construction to initialize
          "sudo apt-get update",

          "sudo apt-get install -y unzip",
          "sudo apt-get install -y git",
          "sudo apt-get install -y mc", // midnight commander; Maggie's favorite Unix shell tool

          "sudo apt-get install -y openjdk-7-jdk", // Java
          "sudo apt-get install -y scala", // Scala

          "sudo wget http://downloads.typesafe.com/play/2.1.5/play-2.1.5.zip", // Play
          "sudo unzip -oq play-2.1.5.zip -d /opt",

          "sudo mkdir /var/play", // where Pointflow goes
          "cd /var/play",
          "sudo git clone https://user:pass@github.com/user/proj",    // pull the source
          "sudo /opt/play-2.1.5/play stage",                                                // package for running
          "sudo cp /var/play/workflow/conf/production.upstart /etc/init/play.conf"          // configure play in upstart
        )
      )
  )
  )

  val pw = new java.io.PrintWriter(new File(args head))
  try pw.write(Json.prettyPrint(packerTemplate)) finally pw.close()
  println("Packer template written to " + args.head)
}