Robust Rails Apps - VanRuby - March 29, 2017

000_robust_rails_apps.md

Robust Rails Apps

Philippe Creux - @pcreux

#vanruby - March 29th, 2017

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010_cover.md

⭐️ Robust Rails Apps ⭐️

😸 Philippe Creux 🐦 @pcreux

💎 vanruby 📆 March 29th, 2017

100_silent_failures.md

Silent Failures

    🙈

110_user_find.rb

# app/controllers/users_controller.rb
def show
  @user = User.find_by_uuid(params[:uuid])
end

# app/views/users/show.html.erb
<%= @user.name %>

112_user_find.rb

# app/controllers/users_controller.rb
def show
  @user = User.find_by_uuid(params[:uuid])
end

# app/views/users/show.html.erb
<%= @user.name %> 💥

# NoMethodError: undefined method `name` for nil

115_user_find.rb

# app/controllers/users_controller.rb
def show
  @user = User.find_by_uuid!(params[:uuid])
end

# app/views/users/show.html.erb
<%= @user.name %>

117_user_find.rb

# app/controllers/users_controller.rb
def show
  @user = User.find_by_uuid!(params[:uuid]) 💥
end

# app/views/users/show.html.erb
<%= @user.name %>


# ActiveRecord::NotFoundError: Can't find user with uuid "foo"

120_hash.rb

require 'open-uri'
require 'json'

json = open("ftp://webftp.vancouver.ca/OpenData/json/LostAnimals.json").read
lost_animals = JSON.parse(json)

p lost_animals.find { |animal| animal["name"] == "Koko" }

123_hash.rb

require 'open-uri'
require 'json'

json = open("ftp://webftp.vancouver.ca/OpenData/json/LostAnimals.json").read
lost_animals = JSON.parse(json)

p lost_animals.find { |animal| animal["name"] == "Koko" }

# => nil 😿

125_hash.rb

require 'open-uri'
require 'json'

json = open("ftp://webftp.vancouver.ca/OpenData/json/LostAnimals.json").read
lost_animals = JSON.parse(json)

p lost_animals.find { |animal| animal.fetch("name") == "Koko" }

# in `fetch': key not found: "name" (KeyError)
# 🙀

127_hash.rb

require 'open-uri'
require 'json'

json = open("ftp://webftp.vancouver.ca/OpenData/json/LostAnimals.json").read
lost_animals = JSON.parse(json)

p lost_animals.find { |animal| animal.fetch("Name") == "Koko" }

# => {"json_featuretype"=>"LostAnimals", "Date"=>"2017-02-06", "Color"=>"Grey/Blk/with White  chest", "Breed"=>"Cat - DSH", "Sex"=>"M", "State"=>"Lost", "Name"=>"Koko", "DateCreated"=>"2017-02-06"}

200_noop.md

Silent Failures

    🙉

205_case.rb

def publish_post(post, timeframe: :now)
  case timeframe
  when :now
    post.publish!
  when :tomorrow
    post.delay(run_at: 1.day.from_now).publish!
  end
end

220_case.rb

def publish_post(post, timeframe: :now)
  case timeframe
  when :now
    post.publish!
  when :tomorrow
    post.delay(run_at: 1.day.from_now).publish!
  end
end

# posts_controller.rb

def publish
  post = Post.find(params[:id])
  publish_post(post, params[:timeframe])
  redirect_to post, notice: "Done! 🎉 "
end

230_case.rb

def publish_post(post, timeframe: :now)
  case timeframe
  when :now
    post.publish!
  when :tomorrow
    post.delay(run_at: 1.day.from_now).publish!
  else
    raise ArgumentError, "Invalid timeframe: #{timeframe.inspect}"
  end
end

# posts_controller.rb

def publish
  post = Post.find(params[:id])
  publish_post(post, params[:timeframe])
  redirect_to post, notice: "Done! 🎉 "
end

# => ArgumentError: Invalid timeframe: "now"

250_silent_failures.rb

def pay(invoice)
  billing_interface.charge!(invoice.amount)

  invoice.update_attributes(
    paid_at: Time.now
  )
end

255_silent_failures.rb

def pay(invoice)
  billing_interface.charge!(invoice.amount)

  invoice.update_attributes(
    paid_at: Time.now
  )
end

# ---

pay(invoice)
invoice.paid_at
# => nil

🤑

260_silent_failures.rb

def pay(invoice)
  billing_interface.charge!(invoice.amount)

  invoice.update_attributes(
    paid_at: Time.now
  )
end

# ---

pay(invoice)
invoice.paid_at
# => nil

🤑

# ---

invoice.valid?
# => false

invoice.errors
# => [ { address: "is invalid" } ]

😰

265_silent_failures.rb

def pay(invoice)
  billing_interface.charge!(invoice.amount)

  invoice.update_attributes!(
    paid_at: Time.now
  )
end

270_silent_failures.rb

def pay(invoice)
  billing_interface.charge!(product.amount)

  invoice.update_attributes!(
    paid_at: Time.now
  )
end

# ---

pay(invoice)
# => ActiveRecord::InvalidRecord ... address in invalid...

😎

271_silent_failures.rb

def pay(invoice)
  billing_interface.charge!(product.amount)  🤡

  invoice.update_attributes!(
    paid_at: Time.now
  )
end

# ---

pay(invoice)
# => ActiveRecord::InvalidRecord ... address in invalid...

🤡

275_silent_failures.rb

def pay(invoice)
  ActiveRecord::Base.transaction do
    invoice.update_attributes!(
      paid_at: Time.now
    )

    billing_interface.charge!(invoice.amount)
  end
end

# ---

pay(invoice)
# => ActiveRecord::InvalidRecord ... address in invalid...

🤓

300_db_contraints.md

Database is your friend™

        📖

310_db_contraints.rb

def limit(feature)
  feature.plan_limit + feature.bonuses + feature.add_ons
end

320_db_contraints.rb

def limit(feature)
  feature.plan_limit + feature.bonuses + feature.add_ons
end

# => TypeError: nil can't be coerced into Fixnum

330_db_contraints.rb

def limit(feature)
  feature.plan_limit + feature.bonuses + feature.add_ons
end

# => TypeError: nil can't be coerced into Fixnum

feature
# => <Feature plan_limit=2 bonuses=nil add_ons=nil>

340_db_contraints.rb

def limit(feature)
  (feature.plan_limit || 0) + (feature.bonuses || 0) + (feature.add_ons || 0)
end

# => 2

🎉

350_db_contraints.rb

def limit(feature)
  feature.plan_limit + feature.bonuses + feature.add_ons
end

# => TypeError: nil can't be coerced into Fixnum

feature
# => <Feature plan_limit=2 bonuses=nil add_ons=nil>

create_table :features do |t|
  t.string  "code"
  t.integer "plan_limit"
  t.integer "bonuses"
  t.integer "add_ons"
end

360_db_contraints.rb

def limit(feature)
  feature.plan_limit + feature.bonuses + feature.add_ons
end

# => TypeError: nil can't be coerced into Fixnum

feature
# => <Feature plan_limit=2 bonuses=nil add_ons=nil>

create_table :features do |t|
  t.string  "code",       null: false
  t.integer "plan_limit", null: false, default: 0
  t.integer "bonuses",    null: false, default: 0
  t.integer "add_ons",    null: false, default: 0
end

370_db_contraints.rb

def limit(feature)
  feature.plan_limit + feature.bonuses + feature.add_ons
end

# => 2

feature
# => <Feature plan_limit=2 bonuses=0 add_ons=0>

create_table :features do |t|
  t.string  "code",       null: false
  t.integer "plan_limit", null: false, default: 0
  t.integer "bonuses",    null: false, default: 0
  t.integer "add_ons",    null: false, default: 0
end

400_db_contraints.rb

class Account < ActiveRecord::Base
  has_one :account_details
end

class AccountDetails < ActiveRecord::Base
  belongs_to :account
end

412_db_contraints.rb

class Account < ActiveRecord::Base
  has_one :account_details
end

class AccountDetails < ActiveRecord::Base
  belongs_to :account
end

account = Account.create!
# => <Account id=1>

414_db_contraints.rb

class Account < ActiveRecord::Base
  has_one :account_details
end

class AccountDetails < ActiveRecord::Base
  belongs_to :account
end

account = Account.create!
# => <Account id=1>

account.account_details
# => nil

account.create_account_details!
# => <AccountDetails account_id=1>

416_db_contraints.rb

class Account < ActiveRecord::Base
  has_one :account_details
end

class AccountDetails < ActiveRecord::Base
  belongs_to :account
end

account = Account.create!
# => <Account id=1>

account.account_details
# => nil

account.create_account_details!
# => <AccountDetails account_id=1>

account.create_account_details!
# => <AccountDetails account_id=2>

420_db_contraints.rb

class Account < ActiveRecord::Base
  has_one :account_details
end

class AccountDetails < ActiveRecord::Base
  belongs_to :account
end

account = Account.create!
# => <Account id=1>

account.account_details
# => nil

account.create_account_details!
# => <AccountDetails account_id=1>

account.create_account_details!
# => <AccountDetails account_id=2>

account.account_details
# => <AccountDetails account_id=1>

account.account_details
# => <AccountDetails account_id=2>

430_db_contraints.rb

class Account < ActiveRecord::Base
  has_one :account_details
end

class AccountDetails < ActiveRecord::Base
  belongs_to :account
end

# ---

add_index :account_details, :account_id, unique: true

432_db_contraints.rb

class Account < ActiveRecord::Base
  has_one :account_details
end

class AccountDetails < ActiveRecord::Base
  belongs_to :account
end

# ---

add_index :account_details, :account_id, unique: true

account = Account.create!
# => <Account id=1>

account.account_details
# => nil

account.create_account_details!
# => <AccountDetails account_id=1>

434_db_contraints.rb

class Account < ActiveRecord::Base
  has_one :account_details
end

class AccountDetails < ActiveRecord::Base
  belongs_to :account
end

# ---

add_index :account_details, :account_id, unique: true

account = Account.create!
# => <Account id=1>

account.account_details
# => nil

account.create_account_details!
# => <AccountDetails account_id=1>

account.create_account_details!
# => <ActiveRecord::UniqueIndexError ....>

440_db_contraints.rb

class Account < ActiveRecord::Base
  has_one :subscription
end

class Subscription < ActiveRecord::Base
  belongs_to :account

  acts_as_paranoid
end

# ---

create_table "subscriptions" do
  t.string    "plan_code", null: false
  t.integer   "account_id", null: false
  t.timestamp "deleted_at"
end

add_index "subscriptions", [:account_id, :deleted_at], unique: true
add_foreign_key "subscriptions", "accounts"

500_wrap_up.rb

user = User.find_by_uuid(params[:uuid])

name = hash['name']

case action
  when :upgrade then # ...
  when :downgrade then # ...
end

user.save

create_table "subscriptions" do
  t.string    "plan_code"
  t.integer   "account_id"
  t.timestamp "deleted_at"
end

510_wrap_up.rb

user = User.find_by_uuid!(params[:uuid])

name = hash.fetch('name')

case action
  when :upgrade then # ...
  when :downgrade then # ...
  else raise ArgumentError
end

user.save!

create_table "subscriptions" do
  t.string    "plan_code", null: false
  t.integer   "account_id", null: false
  t.timestamp "deleted_at"
end

add_index "subscriptions", [:account_id, :deleted_at], unique: true
add_foreign_key "subscriptions", "accounts"

520_wrap_up.md

More infos on

http://bit.ly/robust-rails