elb_register.rb

# Completely untested.

gem_package "amazon-ec2"

aws = search("aws", "main")

Gem.clear_paths
ruby_block do "register_with_elb" do
  do
    require 'amazon-ec2'
    AWS::Base.initialize(:access_key_id => aws['aws_access_key_id'], :secret_access_key => aws['aws_secret_access_key'])
    AWS::ELB::Base.register_instances_with_load_balancer(:load_balancer_name => "name_of_load_balancer")
  end
end

gistfile2.txt

knife data bag show aws main
    {
      "id": "main",
      "ec2_private_key": "private key as a string",
      "ec2_cert": "certificate as a string",
      "aws_account_id": "",
      "aws_secret_access_key": "",
      "aws_access_key_id": ""
    }