Start spot instances

haproxy.rb

require 'aws'
require 'pry'
require 'open-uri'
require 'base64'


class Starter
  def initialize(ec2)
    @ec2 = ec2
  end

  def start!
    request_ids = request_instances
    instance_ids = wait_for_instances(request_ids)
    instances = instance_ids.map { |iid| @ec2.instances[iid] }
    tag_instances(instances)
    wait_for_haproxy(instances)
    instances
  end

  private

  def request_instances
    $stderr.puts('Requesting instances')
    zones = %w(eu-west-1a eu-west-1b eu-west-1c)
    responses = zones.map do |zone|
      @ec2.client.request_spot_instances(spot_request_spec(zone))
    end
    responses.flat_map { |r| r[:spot_instance_request_set].map { |rr| rr[:spot_instance_request_id] } }
  end

  def spot_request_spec(zone)
    {
      spot_price: '0.3',
      instance_count: 1,
      launch_specification: {
        image_id: AMI_WITH_HA_PROXY,
        key_name: FILL_THIS_IN,
        instance_type: 'c1.xlarge',
        iam_instance_profile: {
          arn: 'arn:aws:iam::99999999999:instance-profile/THE_NAME_GOES_HERE'
        },
        placement: {
          availability_zone: zone
        },
        user_data: user_data
      }
    }
  end

  def user_data
    @user_data ||= Base64.encode64(File.read(File.expand_path(PATH_TO_CLOUD_INIT_FILE, __FILE__)))
  end

  def wait_for_instances(request_ids)
    $stderr.puts('Waiting for instances')
    loop do
      response = @ec2.client.describe_spot_instance_requests(:spot_instance_request_ids => request_ids)
      statuses = response[:spot_instance_request_set].map { |rr| rr[:state] }
      if statuses.all? { |s| s == 'active' }
        $stderr.puts('Instances active')
        return response[:spot_instance_request_set].map { |rr| rr[:instance_id] }
      end
      $stderr.puts("Statuses: #{statuses.join(', ')}")
      sleep(5)
    end
  end

  def tag_instances(instances)
    instances.each do |instance|
      zone = instance.availability_zone.split('-').last
      instance.tag('Name', value: "testlb-#{zone}")
      instance.tag('HAProxy', value: 'lb')
      instance.tag('Role', value: 'lb')
      instance.tag('Environment', value: 'test')
    end
    $stderr.puts('Instances tagged')
  end

  def wait_for_haproxy(instances)
    $stderr.puts('Waiting for HAProxy')
    dns_names = Hash[instances.map { |i| [i.tags['Name'], i.public_dns_name] }]
    dns_names.each do |name, dns_name|
      $stderr.puts("#{name} #{dns_name}")
    end
    loop do
      break if dns_names.all? do |name, dns_name|
        begin
          open("http://#{dns_name}/").read
          $stderr.puts("HAProxy on #{name} started")
          true
        rescue => e
          false
        end
      end
    end
    $stderr.puts('HAProxy started on all instances')
  end
end

ec2 = AWS::EC2.new(ec2_endpoint: 'ec2.eu-west-1.amazonaws.com')
Starter.new(ec2).start!