ec2_example.rb

require 'aws-sdk-core'
require 'colorize'
require 'retries'

ec2 = Aws::EC2::Client.new(region: 'us-west-2')

## Security Groups

puts '===> creating security groups'.green

['web-sg', 'db-sg', 'lb-sg'].each do |group|
  begin
    ec2.create_security_group(
      group_name: group,
      description: "#{group} security group",
    )
  rescue Aws::EC2::Errors::InvalidGroupDuplicate
    puts "skipping #{group}".yellow
  end
end

puts '===> configuring security groups'.green

begin
  ec2.authorize_security_group_ingress(
    group_name: 'lb-sg',
    ip_permissions: [
      {
        ip_protocol: 'tcp',
        to_port: 80,
        from_port: 80,
        ip_ranges: [
          {
            cidr_ip: '0.0.0.0/0',
          },
        ]
      }
    ]
  )
rescue Aws::EC2::Errors::InvalidPermissionDuplicate
  puts "skipping".yellow
end

begin
  ec2.authorize_security_group_ingress(
    group_name: 'web-sg',
    source_security_group_name: 'lb-sg',
  )
rescue Aws::EC2::Errors::InvalidPermissionDuplicate
  puts "skipping".yellow
end

begin
  ec2.authorize_security_group_ingress(
    group_name: 'db-sg',
    source_security_group_name: 'web-sg',
  )
rescue Aws::EC2::Errors::InvalidPermissionDuplicate
  puts "skipping".yellow
end

## Instances

puts '===> creating instances'.green

ec2.run_instances(
  image_id: 'ami-2d9add1d',
  min_count: 2,
  max_count: 2,
  security_groups: ['web-sg'],
  instance_type: 't1.micro',
)

ec2.run_instances(
  image_id: 'ami-2d9add1d',
  min_count: 1,
  max_count: 1,
  security_groups: ['db-sg'],
  instance_type: 't1.micro',
)

## Load Balancer

puts '===> creating load balancer'.green

resp = ec2.describe_security_groups(group_names: ['lb-sg'])
security_group_id = resp.data.security_groups.first.group_id

elb = Aws::ElasticLoadBalancing::Client.new(region: 'us-west-2')

elb.create_load_balancer(
  load_balancer_name: 'lb-1',
  listeners: [
    {
      protocol: 'tcp',
      load_balancer_port: 80,
      instance_protocol: 'tcp',
      instance_port: 80,
    },
  ],
  availability_zones: ['us-west-2b'],
  security_groups: [security_group_id],
)

puts '===> configuring load balancer'.green

resp = ec2.describe_security_groups(group_names: ['web-sg'])
security_group_id = resp.data.security_groups.first.group_id

resp = ec2.describe_instances(
filters: [
    {
      name: 'instance.group-id',
      values: [security_group_id],
    },
  ],
)

web1 = resp.data.reservations.first.instances[0].instance_id
web2 = resp.data.reservations.first.instances[1].instance_id

elb.register_instances_with_load_balancer(
  load_balancer_name: 'lb-1',
  instances: [
    {
      instance_id: web1,
    },
    {
      instance_id: web2,
    },
  ],
)

puts '===> and sleep'
sleep 10

puts '===> deleting instances'.red

resp = ec2.describe_security_groups(group_names: ['db-sg'])
security_group_id = resp.data.security_groups.first.group_id

resp = ec2.describe_instances(
filters: [
    {
      name: 'instance.group-id',
      values: [security_group_id],
    },
  ],
)

db1 = resp.data.reservations.first.instances[0].instance_id


ec2.terminate_instances(
  instance_ids: [web1, web2, db1],
)

puts '===> deleting load balancer'.red

elb.delete_load_balancer(
  load_balancer_name: 'lb-1',
)

puts '===> deleting security groups'.red

with_retries(:max_tries => 5, :base_sleep_seconds => 30.0,
  :max_sleep_seconds => 120.0, :rescue => Aws::EC2::Errors::DependencyViolation) do |attempt_number|
    puts "trying to delete (#{attempt_number}/5)".yellow
    ['db-sg', 'web-sg', 'lb-sg'].each do |group|
      begin
        ec2.delete_security_group(
          group_name: group
        )
      rescue Aws::EC2::Errors::InvalidGroupNotFound
        # already deleted
      end
    end
  end

Hah, always love the sleeps... in the past I've polled the status api on a 1 second interval.