AWS EC2のインスタンス状態をポーリングしてZeroMQにPub/Subするデモ。

README.md

Prerequisite

$ brew install zeromq
$ ARCHFLAGS="-arch x86_64" gem install zmq -- --with-zmq-dir=/usr/local
$ gem install amazon-ec2

Run

Terminal 1:

$ ruby zmq-publisher.rb
-> running i-fe4ac2ff 2011-04-01T07:44:02.000Z
-> stopping i-fe4ac2ff 2011-04-01T07:44:02.000Z

Terminal 2:

$ ruby zmq-subscriber.rb
i-fe4ac2ff が起動しました
i-fe4ac2ff が停止しました

zmq-publisher.rb

require 'zmq'
require 'AWS'

ZMQ_PORT = 5000
POLLING_INTERVAL = 10
AWS_CONFIG = {
  :access_key_id => '***',
  :secret_access_key => '***',
  :server => 'ec2.ap-northeast-1.amazonaws.com',  # Tokyo
}

ec2 = AWS::EC2::Base.new(AWS_CONFIG)

ctx = ZMQ::Context.new
sock = ctx.socket(ZMQ::PUB)
sock.bind("tcp://127.0.0.1:#{ZMQ_PORT}")

loop do
  result = ec2.describe_instances
  if result.reservationSet
    result.reservationSet.item.each do |reservation|
      reservation.instancesSet.item.each do |instance|
        state = instance.instanceState.name
        identifier = instance.instanceId
        launch_time = instance.launchTime
        message = "#{state} #{identifier} #{launch_time}"
        puts "-> #{message}"
        sock.send message
      end
    end
  end
  sleep POLLING_INTERVAL
end

zmq-subscriber.rb

# -*- coding: utf-8 -*-
require 'zmq'

ZMQ_PORT = 5000

ctx = ZMQ::Context.new
sock = ctx.socket(ZMQ::SUB)
sock.connect("tcp://127.0.0.1:#{ZMQ_PORT}")
sock.setsockopt(ZMQ::SUBSCRIBE, 'running')
sock.setsockopt(ZMQ::SUBSCRIBE, 'stopped')

running_instances = []

loop do
  message = sock.recv
  values = message.split(' ', 3)
  state = values[0]
  identifier = values[1]

  if state == 'running' && !running_instances.include?(identifier)
    running_instances << identifier
    puts "#{identifier} が起動しました"
  end

  if state == 'stopped' && running_instances.include?(identifier)
    running_instances.delete identifier
    puts "#{identifier} が停止しました"
  end
end