Digital Ocean's presentation from the Ruby Dev Stackup held at The Flatiron School on 5/6

1. Riding the Rails
@
DigitalOcean

2. • Shared business logic as an engine
• Form objects
• MySQL table as KV store
• Abusing ASN for cleanliness

3. gem 'core',
git: 'https://githubenterprise/digitalocean/core',
ref: '623ac1e785e092f7369d5cfa7e56ea2e98fb2e20'
“Core”
Our Rails Engine in Reverse

4. “Core”
Our Rails Engine in Reverse
gem 'core',
git: 'https://githubenterprise/digitalocean/core',
ref: '623ac1e785e092f7369d5cfa7e56ea2e98fb2e20'

5. # lib/blorgh/engine.rb
module Blorgh
class Engine < ::Rails::Engine
isolate_namespace Blorgh
config.to_prepare do
Dir.glob(Rails.root + "app/decorators/**/*_decorator*.rb").each do |c|
require_dependency(c)
end
end
end
end
# MyApp/app/decorators/models/blorgh/post_decorator.rb
Blorgh::Post.class_eval do
def time_since_created
Time.current - created_at
end
end
:thumbsdown:

6. # MyApp/app/models/blorgh/post.rb
class Blorgh::Post < ActiveRecord::Base
include Blorgh::Concerns::Models::Post
def time_since_created
Time.current - created_at
end
def summary
"#{title} - #{truncate(text)}"
end
end
:thumbsdown:

7. # Blorgh/lib/concerns/models/post
module Blorgh::Concerns::Models::Post
extend ActiveSupport::Concern
# 'included do' causes the included code to be evaluated in the
# context where it is included (post.rb), rather than being
# executed in the module's context (blorgh/concerns/models/post).
included do
attr_accessor :author_name
belongs_to :author, class_name: "User"
before_save :set_author
private
def set_author
self.author = User.find_or_create_by(name: author_name)
end
end
end

8. require_dependency Core::Engine.root.join('app', 'models', 'droplet').to_s
class Droplet
BACKUP_CHARGE_PERCENTAGE = 0.20
def monthly_backup_price
self.size.monthly_price * BACKUP_CHARGE_PERCENTAGE
end
end
:thumbsup:

9. Previously...
# app/controllers/events_controller.rb
event = Event.new(
:event_scope => 'droplet',
:event_type => params[:event_type], # from the route
:droplet_id => params[:droplet_id],
:image_id => params[:image_id],
:size_id => params[:size_id],
:user_id => current_user.id,
:name => name
)
# app/models/event.rb
# Validations Based on Event Type
case self.event_type
when 'resize'
errors.add(:size_id, "...") if size_id == droplet.size_id
errors.add(:size_id, "...") unless Size.active.include? size_id
end

10. class Resize
extend ActiveModel::Naming
include ActiveModel::Conversion
include ActiveModel::Validations
include Virtus
attribute :size, Size
attribute :user, User
attribute :droplet, Droplet
validates :size,
allowed_size: true,
presence: true
def save
if valid?
event.save!
else
false
end
end
def persisted?
false
end
def event
@_event ||= EventFactory.build(:resize, event_params)
end
end

11. # app/views/resizes/_form.erb
= form_for [@droplet, Resize.new] do |f|
= render 'sizes', sizes: @sizes_available_for_resize, form: f
= f.submit 'Resize'
class ResizesController < ApplicationController
def create
droplet = current_user.droplets.find(params[:droplet_id])
size = Size.active.where(id: params[:size_id]).first
resize = Resize.new(droplet: droplet, size: size)
if resize.save
redirect_to resize.droplet, notice: 'Your resize is processing'
else
redirect_to resize.droplet, alert: resize.errors.first
end
end
end

12. <3Virtus
• Validations are contextual
• Slims down god objects
• Can be tested without ActiveRecord
• Makes testing ActiveRecord classes easier

13. WARNING:
YOU
PROBABLY
SHOULD
NOT
DO
THIS

14. CREATE TABLE `user_properties` (
`user_id` int(11) NOT NULL,
`name` varchar(32) NOT NULL DEFAULT '',
`value` varchar(255) NOT NULL DEFAULT '',
PRIMARY KEY (`user_id`,`name`),
KEY `name` (`name`,`value`),
KEY `user_id` (`user_id`,`name`,`value`)
)
class User
include Propertable
property :marked_as_sketchy_at, nil, :date_time
property :marked_as_verified_at, nil, :date_time
property :marked_as_abuse_at, nil, :date_time
property :marked_as_hold_at, nil, :date_time
property :marked_as_suspended_at, nil, :date_time
property :marked_as_review_at, nil, :date_time
end

15. module Propertable
def property(name, default, type = :string)
key = name.to_s
props = class_variable_get(:@@properties)
props[key] = default
define_method(key) do
property = __read_property__(key)
if property.nil? || property == default
default
else
Propertable::Coercer.call(property.value, property.value.class, type)
end
end
define_method("#{key}?") do
!!public_send(key)
end
define_method("#{key}=") do |value|
begin
coerced_value = Propertable::Coercer.call(value, value.class, type)
rescue
coerced_value = default
end
coerced_value = Propertable::Coercer.call(coerced_value, type.class, :string)
property = __write_property__(key, coerced_value)
end
end
end

16. ASN = ActiveSupport::Notifications

17. INSTRUMENT
EVERYTHING!

18. $statsd = Statsd.new(statsd_ip).tap { |s| s.namespace = Rails.env }
# Request Times
ActiveSupport::Notifications.subscribe /process_action.action_controller/ do |*args|
event = ActiveSupport::Notifications::Event.new(*args)
status = event.payload[:status]
key = "requests.cloud"
$statsd.timing "#{key}.time.total", event.duration
$statsd.timing "#{key}.time.db", event.payload[:db_runtime]
$statsd.timing "#{key}.time.view", event.payload[:view_runtime]
$statsd.increment "#{key}.status.#{status}"
end
# SQL Queries
ActiveSupport::Notifications.subscribe 'sql.active_record' do |*args|
event = ActiveSupport::Notifications::Event.new(*args)
key = 'queries.cloud'
$statsd.increment key
$statsd.timing key, event.duration
end

20. module Instrumentable
extend ActiveSupport::Concern
included do
build_instrumentation
end
module ClassMethods
def build_instrumentation
key = name.underscore + '.callbacks'
after_commit(on: :create) do |record|
ASN.instrument key, attributes: record.attributes, action: 'create'
end
after_rollback do |record|
ASN.instrument key, attributes: record.attributes, action: 'rollback'
end
end
end
end

21. ActiveSupport::Notifications.subscribe 'event.callbacks' do |*args|
event = ActiveSupport::Notifications::Event.new(*args)
type_id = event.payload[:attributes]['event_type_id']
action = event.payload[:action]
EventInstrumenter.perform_async(type_id, action)
end

22. after_commit(on: :update) do |record|
ASN.instrument key,
attributes: record.attributes,
changes: record.previous_changes,
action: 'update'
end

23. class TicketNotifier < BaseNotifier
setup :ticket
def created(ticket)
notify_about_admin_generated_ticket!(ticket) if ticket.opened_by_admin?
end
def updated(ticket, changes)
if category = modification(changes, 'category')
notify_networking(ticket) if category == 'networking'
notify_about_escalated_ticket(ticket) if category == 'engineering'
end
end
private
# TODO: move to base
def modification(changes, key)
changes.has_key?(key) && changes[key].last
end
end

24. ESB = ASN = ActiveSupport::Notifications

25. We’re Hiring!

26. module Rack
class Audit
def call(env)
audit = Thread.current[:audit] = {}
audit[:request] = Rack::Request.new(env)
@app.call(env)
end
end
end