Centurion with etcd Proof-of-Concept

fooservice.rake

namespace :environment do
  require 'etcd'

  def hash_value_for(item)

    if item.is_a?(Array)
      return item.inject({}) { |memo, x| memo.merge(hash_value_for(x)) }
    end

    if item.directory?
      return { File.basename(item.key) => hash_value_for(item.children) }
    end

    return { File.basename(item.key) => item.value }
  end

  def etcd_client
    @etcd_client ||= Etcd.client(host: '127.0.0.1', port: '4001')
  end

  def etcd_configuration_for(service)
    # TODO look at current_environment and talk to the right etcd server
    env = hash_value_for(etcd_client.get("/services/#{service}/", recursive: true))
    raise "Bad configuration!" if env.empty?

    env[service]['ports'].each do |(container_port, to_host_port)|
      host_port to_host_port, container_port: container_port
    end

    env[service]['hosts'].each do |(hostname, state)|
      host hostname
    end
  end

  task :common do
    set :image, 'fooservice'
  end

  desc 'Staging environment'
  task :staging => :common do
    set_current_environment(:staging)
    etcd_configuration_for('fooservice')
  end
end

Services Layout.md

Services Layout

The following code run from inside a Ruby script that has loaded the etcd gem would create the necessary keys to deploy using the above code.

client.set('/services/fooservice/ports/3021', value: 9292)
client.set('/services/fooservice/env/TESTING_URL', value: 'http//foo.example.com/asdf')

client.set('/services/fooservice/hosts/yourco-staging-foo-1.example.com', value: 'up')
client.set('/services/fooservice/hosts/yourco-staging-foo-2.example.com', value: 'up')
client.set('/services/fooservice/hosts/yourco-staging-foo-3.example.com', value: 'up')

That assigns port 3021 on the host to 9292 in the container, "http://foo.example.com/asdf" to the TESTING_URL environment variable and specifies three hosts to deploy to.

Currently host volume mounts don't fit well into this schema as the key doesn't work well.This needs to be figured out.