For a list of instances returned from a chef search, terminate instances, release any elastic ips, and delete any attached volumes.

delete-instance.rb

require 'time'
require 'json'
require 'pp'
require 'open3'

class DeleteShare
  def initialize
    @instances = Hash.new {|h,k| h[k] = [] }
    @public_ips = Hash.new {|h,k| h[k] = [] }
    @volumes = Hash.new {|h,k| h[k] = [] }
    @eipallocs = Hash.new {|h,k| h[k] = [] }
  end

  def run
    parse_chef_json_to_instance_ids
    fetch_instance_details
    fetch_address_details
    
    terminate_instances
    release_ips
    delete_volumes
  end
  
  private
    
  def parse_chef_json_to_instance_ids
    # created with: 
    #     knife search -F json '(chef_environment:prd OR chef_environment:prd-b) AND recipe:clearslide-screenshare AND fqdn:share*' -a ec2 > old_share.json
    data = JSON.parse(File.read('old_share.json'))
    data.fetch('rows').each do |row|
      row.each do |host, wrapper|
        attributes = wrapper.fetch('ec2')
        parse_each_host(host, attributes)
      end
    end
  end

  def parse_each_host(host, attributes)  
    region = az_to_region attributes.fetch('placement_availability_zone')  
    instance_id = attributes.fetch('instance_id')
    public_ipv4 = attributes.fetch('public_ipv4')
    
    @instances[region] << instance_id
    @public_ips[region] << public_ipv4
  end  
  
  def az_to_region(str)
    str[0...-1]
  end
  
  def fetch_instance_details
    @instances.each do |region, instances|
      json = exec "aws --region=#{region} ec2 describe-instances --instance-ids #{instances.join(" ")}"
      data = JSON.parse(json)
      data.fetch("Reservations").each do |reservation|
        reservation.fetch("Instances").each do |instance|
          instance.fetch("BlockDeviceMappings").each do |device|
            ebs = device.fetch("Ebs")
            volume_id = ebs.fetch("VolumeId")
            @volumes[region] << volume_id
          end
        end
      end
    end 
  end
  
  def fetch_address_details
    @public_ips.each do |region, ips|
      json = exec "aws --region=#{region} ec2 describe-addresses --public-ips #{ips.join(" ")}"
      data = JSON.parse(json)
      data.fetch("Addresses").each do |address|
        @eipallocs[region] << address["AllocationId"]
      end
    end
  end
    
  def terminate_instances
    @instances.each do |region, instances|
      exec "aws --region=#{region} ec2 terminate-instances --instance-ids #{instances.join(" ")}"
    end    
  end
  
  def release_ips
    @eipallocs.each do |region, ids|
      ids.each do |id|
        exec "aws --region=#{region} ec2 release-address --allocation-id #{id}"
      end
    end    
  end
  
  def delete_volumes
    @volumes.each do |region, volumes|
      volumes.each do |id|
        exec "aws --region=#{region} ec2 delete-volume --volume-id #{id}"
      end
    end    
  end  

  def exec(command)
    info "exec #{command}"
    `#{command}`
  end

  def info(msg)
    puts("#{Time.now.iso8601(3)} #{msg}")
  end    
end

DeleteShare.new.run