A custom Ohai plugin which provides EC2 instance tags

ec2_tags.rb

require 'json'

Ohai.plugin(:EC2Tags) do
  provides "ec2/tags"

  depends "ec2"

  collect_data do
    region = ec2['placement_availability_zone'].chop
    instance_id = ec2['instance_id']

    so = shell_out("aws ec2 describe-tags --region #{region} --filters Name=resource-type,Values=instance Name=resource-id,Values=#{instance_id}")
    if so.exitstatus == 0
      ec2[:tags] = JSON.parse(so.stdout)['Tags'].map {|tag| {tag['Key'] => tag['Value']}}.inject(Mash.new, :merge)
    end
  end
end

Path example: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-7.4.0/lib/ohai/plugins/ec2_tags.rb

$ ohai ec2/tags
{
  "EIP": "1.1.1.1",
  "Name": "example-host1"
}