Files to construct a Chef cookbook for creating a "canary" instance (a box that simply announces itself to CoudWatch, to ensure that egress traffic from private subnets is successfully making its way through your NAT boxes).

attributes__default.rb

default[:deliv_canary][:cron_name] = 'canary'
default[:deliv_canary][:region] = 'us-east-1'
default[:deliv_canary][:namespace] = 'Canary'
default[:deliv_canary][:metric_name] = 'Chirps'
default[:deliv_canary][:unit] = 'Count'
default[:deliv_canary][:value] = 1
default[:deliv_canary][:dimensions] = {
  AZ: node[:opsworks][:instance][:availability_zone],
  Environment: node[:deliv_canary][:environment],
  VPC: node[:opsworks][:stack][:vpc_id],
}.to_a.sort.map { |pair| pair.join('=') }.join(',')

recipes__default.rb

cron node[:deliv_canary][:cron_name] do
  command %Q(aws cloudwatch put-metric-data
             --region #{node[:deliv_canary][:region]}
             --namespace #{node[:deliv_canary][:namespace]}
             --metric-name #{node[:deliv_canary][:metric_name]}
             --unit #{node[:deliv_canary][:unit]}
             --value #{node[:deliv_canary][:value]}
             --dimensions #{node[:deliv_canary][:dimensions]}).gsub(/\s+/, ' ')
end

include_recipe 'deliv_canary::list_crontab'

recipes__kill.rb

cron node[:deliv_canary][:cron_name] do
  action :delete
end

include_recipe 'deliv_canary::list_crontab'

recipes__list_crontab.rb

ruby_block 'list_crontab' do
  block do
    Chef::Log.info("Crontab for #{`whoami`.chomp} is currently: \n#{`crontab -l`}")
  end
end