List all instances in an ELB, and all ELBs the instances are in.

README.md

Usage

$ ruby ./instance_to_elb.rb

Output

The output is a JSON containing the mapping of LB->instances as well as Instance->LBs.

instance_to_elb.rb

require 'rubygems'
require 'json'
require 'aws-sdk'

ec2 = AWS::EC2.new
aws_elb = AWS::ELB.new

instances = {}
elbs = {}
parent = {}

aws_elb.load_balancers.each do |elb|
  puts elb.name
  elbs[elb.name] = Array.new
  elb.instances.each do |instance|
    elbs[elb.name].push(instance.tags.Name)
    if (instances[instance.tags.Name].nil?)
      instances[instance.tags.Name] = Array.new
    end
    instances[instance.tags.Name].push(elb.name)
  end
end

parent['elb-to-instance'] = elbs
parent['instance-to-elb'] = instances

puts JSON.pretty_generate(parent)