This presentation will talk about the challenges of building large Ruby web applications and how to maintain existing ones. I will use examples adapted from real applications that I worked on during my 10 years of experience with Ruby outlining: technical limitations of the language, how to use a modular dependency structure to enforce boundaries in complex domains.

1. build and maintain large Ruby
applications
Enrico Teotti - @agenteo - http://teotti.com
starting shortly

2. build and maintain large Ruby
applications
Enrico Teotti - @agenteo - http://teotti.com
http://www.slideshare.net/agenteo

3. http://pivotal.io/careers

5. crowbar.rb spec.description = ”Builds and maintains large Ruby apps”

8. –Any Java developer always ;-)
“Ruby is a toy language.”

9. automated
testing
team
diligence
local Ruby
gems

10. http://teotti.com/cognitive-overload-in-software-development/

12. Ruby files in a project are like ingredients in a recipe

14. yeasthoney
salt
milk flourwaterlard
sugar
arugula
squacqueroneprosciutto

15. piadina
yeasthoney
salt
milk flourwaterlard
sugar
arugula
squacqueroneprosciutto

19. 3 months later

20. piadina
the curse of
knowledge
yeasthoney
salt
milk flourwaterlard
sugar
arugula
squacqueroneprosciutto

21. 6 months later
– The law of continuing change (1974) Lehman, M
“Any software system used in the real-world must change or
become less and less useful in that environment.”
– The law of increasing complexity (1974) Lehman, M
“As a program evolves, it becomes more complex, and extra
resources are needed to preserve and simplify its structure.”

22. biscuits
mozzarella
sunflower oil
carrots
eggs
tomato puree
basil
mascarpone
coffee
cacao
yeasthoney
salt
milk flourwaterlard
sugar
arugula
squacqueroneprosciutto
oregano

23. sunflower oil
carrots
gs
tomato puree
basil
mascarpone
coffee
cacao
yeasthoney
salt
milk flourwaterlard
sugar
arugula
squacqueroneprosciutto
oregano
piadina
pizza margherita
tiramisu
carrot cake

24. white ingredients
green ingredients
red ingredients
yellowish ingredients
orange ingredients
dark ingredients

25. white ingredients
green ingredients
classes grouped
by design pattern
ls -l app/
controllers
helpers
models
presenters
services
serializers
strategies
utils
views
http://teotti.com/application-directories-named-as-architectural-patterns-antipattern/

26. piadina
pizza margherita
tiramisu
carrot cake

28. namespaces

29. # lib/blog/after_publish.rb
module Blog
class AfterPublish
private
def subscribe_blogger_to_promotion
Promotions::Submission.new
end
end
end
# lib/promotions/new_member.rb
module Promotions
class Submission
private
def fetch_member(id)
# lib/membership/finder.rb
Membership::Finder.new(id)
end
end
end
promotionsblog membership
namespaces
context context

30. promotions
name
finder
blog membership
main Ruby application
1 year
lib
http://teotti.com/building-and-maintaing-large-ruby-on-rails-applications-for-3-years/
DB
team of 5

31. promotions
room
decorator
name
finder
blog membershiprecipes
main Ruby application
comments
3 years
lib
DB
team of 5

32. that’s the Ruby way
ma noooooooooo

33. piadina worktop
tiramisu worktop
shared worktop
carrot cake worktop
pizza worktop

34. local Ruby gems

37. A
main Ruby application
piadina gem

38. Apiadina gem
pizza gem
C
shared
ingredients
gem
B
main Ruby application

39. Apiadina gem
pizza gem
C
shared
ingredients
gem
B
main Ruby application
spec.add_dependency "shared_ingredients"
# local_gems/pizza/pizza.gemspec

40. Apiadina gem
pizza gem
C
shared
ingredients
gem
main Ruby application
spec.add_dependency "shared_ingredients"
# local_gems/piadina/piadina.gemspec
B

42. piadina gem
pizza gem
C
shared
ingredients
gem
B
main Ruby application
desserts gem
D
A

44. piadina gem
pizza gem
C
shared
ingredients
gem
B
main Ruby application
desserts gem
D
A
E
calzone gem
pizza dough gem
F

45. piadina gem
pizza gem
C
shared
ingredients
gem
B
main Ruby application
desserts gem
D
A
E
calzone gem
pizza dough gem
F
Conway’s Law
“organizations which design systems … are constrained to produce designs which
are copies of the communication structures of these organizations"

46. piadina gem
pizza gem
shared
ingredients
gem
main Ruby application
desserts gem
D
A
calzone gem
pizza dough gem
F
B
E
C

47. http://teotti.com/create-dependency-structures-with-local-ruby-gems/
code & examples

48. A
C
D
B
E
your health plan
drug information
claims platform
product
information
membership
gem
gem
gem
gem
gem
dependency
main Ruby application
Sinatra / Rails / Hanami

49. !"" Gemfile
!"" Gemfile.lock
!"" local_gems
!"" run.rb
#"" spec
ruby script that
triggers entry point
gem’s behaviour
require 'health_plan'
subscriber_id = 'ASE123456789'
aggregated_drug_information = HealthPlan::Aggregator.new(subscriber_id)
puts aggregated_drug_information.details
main Ruby application

50. !"" Gemfile
!"" Gemfile.lock
!"" local_gems
!"" run.rb
#"" spec
path 'local_gems' do
gem 'health_plan'
end
source 'https://rubygems.org'
group :test do
gem 'rspec'
end
bundler’s Gemfile uses
a path directive to find
local gems
main Ruby application

51. !"" Gemfile
!"" Gemfile.lock
!"" local_gems
!"" run.rb
#"" spec
bundler’s Gemfile uses
a path directive to find
local gems
path 'local_gems' do
gem 'health_plan'
end
source 'https://rubygems.org'
group :test do
gem 'rspec'
end
main Ruby application
http://teotti.com/gemfiles-hierarchy-in-ruby-on-rails-component-based-architecture/

52. !"" Gemfile
!"" Gemfile.lock
!"" local_gems
!"" run.rb
#"" spec
directory where your local gems are
$ cd local_gems
$ bundle gem health_plan
create health_plan/Gemfile
create health_plan/Rakefile
create health_plan/LICENSE.txt
create health_plan/README.md
create health_plan/.gitignore
create health_plan/health_plan.gemspec
create health_plan/lib/health_plan.rb
create health_plan/lib/health_plan/version.rb
Initializing git repo in /Users/me/code/lab/gem-dependency-structure/local_gems/health_plan
$ rm -Rf health_plan/.git*
bundle gem can create gems
main Ruby application

53. # local_gems/health_plan/health_plan.gemspec
lib = File.expand_path('../lib', __FILE__)
$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
require 'health_plan/version'
Gem::Specification.new do |spec|
spec.name = "health_plan"
spec.version = HealthPlan::VERSION
spec.authors = ["Enrico Teotti"]
spec.email = ["enrico.teotti@gmail.com"]
spec.summary = %q{Write a short summary. Required.}
spec.description = %q{Write a longer description. Optional.}
spec.homepage = ""
spec.license = "MIT"
spec.files = `git ls-files -z`.split("x0")
spec.executables = spec.files.grep(%r{^bin/}) { |f| File.basename(f) }
spec.test_files = spec.files.grep(%r{^(test|spec|features)/})
spec.require_paths = ["lib"]
spec.add_development_dependency "bundler", "~> 1.7"
spec.add_development_dependency "rake", "~> 10.0"
!"" Gemfile
!"" Gemfile.lock
!"" local_gems
$ #"" health_plan
!"" run.rb
#"" spec
spec.add_development_dependency "rspec", "3.4.0"
end
your health plan

54. # local_gems/health_plan/health_plan.gemspec
lib = File.expand_path('../lib', __FILE__)
$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
require 'health_plan/version'
Gem::Specification.new do |spec|
spec.name = "health_plan"
spec.version = HealthPlan::VERSION
spec.authors = ["Enrico Teotti"]
spec.email = ["enrico.teotti@gmail.com"]
spec.summary = %q{Write a short summary. Required.}
spec.description = %q{Write a longer description. Optional.}
spec.homepage = ""
spec.license = "MIT"
spec.files = `git ls-files -z`.split("x0")
spec.executables = spec.files.grep(%r{^bin/}) { |f| File.basename(f) }
spec.test_files = spec.files.grep(%r{^(test|spec|features)/})
spec.require_paths = ["lib"]
spec.add_development_dependency "bundler", "~> 1.7"
spec.add_development_dependency "rake", "~> 10.0"
!"" Gemfile
!"" Gemfile.lock
!"" local_gems
$ #"" health_plan
!"" run.rb
#"" spec
spec.add_development_dependency "rspec", "3.4.0"
end
your health plan

55. # local_gems/health_plan/spec/health_plan/aggregator_spec.rb
require 'spec_helper'
describe HealthPlan::Aggregator do
describe "#details" do
it "should not throw exceptions" do
aggregator = HealthPlan::Aggregator.new(12345)
expect(aggregator.details).to eq({ name: 'The full package plan'})
end
end
end
your health plan
!"" Gemfile
!"" Gemfile.lock
!"" local_gems
$ #"" health_plan
!"" run.rb
#"" spec

56. # local_gems/health_plan/lib/health_plan/aggregator.rb
module HealthPlan
class Aggregator
def initialize(id)
@subscriber_id = id
end
def details
{ name: 'The full package plan'}
end
end
end
# local_gems/health_plan/lib/health_plan.rb
require "health_plan/version"
require "health_plan/aggregator"
module HealthPlan
end
gem entry point
your health plan
!"" Gemfile
!"" Gemfile.lock
!"" local_gems
$ #"" health_plan
!"" run.rb
#"" spec

57. !"" Gemfile
!"" Gemfile.lock
!"" local_gems
$ !"" drug_information
$ #"" health_plan
!"" run.rb
#"" spec
your health plan
drug information
main Ruby application
$ cd local_gems
$ bundle gem drug_information
create drug_information/Gemfile
create drug_information/Rakefile
create drug_information/LICENSE.txt
create drug_information/README.md
create drug_information/.gitignore
create drug_information/drug_information.gemspec
create drug_information/lib/drug_information.rb
create drug_information/lib/drug_information/version.rb
drug information

58. # local_gems/health_plan/spec/health_plan/aggregator_spec.rb
require 'spec_helper'
describe HealthPlan::Aggregator do
describe "#details" do
let(:fetched_drugs) { 'something' }
before do
fetcher_double = double('DrugInformation::Fetcher', details: fetched_drugs)
allow(DrugInformation::Fetcher).to receive(:new).and_return(fetcher_double)
end
it "should not throw exceptions" do
aggregator = HealthPlan::Aggregator.new(12345)
expect(aggregator.details).to eq({ name: 'The full package plan’,
drugs: fetched_drugs })
end
end
end
your health plan
!"" Gemfile
!"" Gemfile.lock
!"" local_gems
$ !"" drug_information
$ #"" health_plan
!"" run.rb
#"" spec

59. your health plan
lib = File.expand_path('../lib', __FILE__)
$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
require 'health_plan/version'
Gem::Specification.new do |spec|
spec.name = "health_plan"
spec.version = HealthPlan::VERSION
spec.authors = ["Enrico Teotti"]
spec.email = ["enrico.teotti@gmail.com"]
spec.summary = %q{Write a short summary. Required.}
spec.description = %q{Write a longer description. Optional.}
spec.homepage = ""
spec.license = "MIT"
spec.files = `git ls-files -z`.split("x0")
spec.executables = spec.files.grep(%r{^bin/}) { |f| File.basename(f) }
spec.test_files = spec.files.grep(%r{^(test|spec|features)/})
spec.require_paths = ["lib"]
spec.add_development_dependency "bundler", "~> 1.7"
spec.add_development_dependency "rake", "~> 10.0"
spec.add_development_dependency "rspec", "3.4.0"
spec.add_dependency "drug_information"
end
# local_gems/health_plan/health_plan.gemspec
!"" Gemfile
!"" Gemfile.lock
!"" local_gems
$ !"" drug_information
$ #"" health_plan
!"" run.rb
#"" spec

60. your health plan
# local_gems/health_plan/Gemfile
!"" Gemfile
!"" Gemfile.lock
!"" local_gems
$ !"" drug_information
$ #"" health_plan
!"" run.rb
#"" spec
path '..'
source 'https://rubygems.org'
‘..’ represents the parent directory
gemspec

61. your health plan
# local_gems/health_plan/Gemfile
!"" Gemfile
!"" Gemfile.lock
!"" local_gems
$ !"" drug_information
$ #"" health_plan
!"" run.rb
#"" spec
path '..'
source 'https://rubygems.org'
look for dependencies within the gem specification file
gemspec

62. # local_gems/health_plan/lib/health_plan/aggregator.rb
module HealthPlan
class Aggregator
def initialize(id)
@subscriber_id = id
end
def details
fetched_drug_info = DrugInformation::Fetcher.new(@subscriber_id)
{ name: 'The full package plan', drugs: fetched_drug_info.details }
end
end
end
# local_gems/health_plan/lib/health_plan.rb
require "health_plan/version"
require "health_plan/aggregator"
require "drug_information"
module HealthPlan
end
gem entry point
your health plan
!"" Gemfile
!"" Gemfile.lock
!"" local_gems
$ !"" drug_information
$ #"" health_plan
!"" run.rb
#"" spec
require dependent gem
http://teotti.com/create-dependency-structures-with-local-ruby-gems/

63. $ bundle viz
!"" Gemfile
!"" Gemfile.lock
!"" local_gems
$ !"" drug_information
$ #"" health_plan
!"" run.rb
#"" spec
main Ruby application
https://github.com/shageman/cobradeps

64. automated
testing

65. A
C
D
B
E
main Ruby application
unit tested
unit tested
unit testedunit tested
unit tested
acceptance tests

66. A
C
main Ruby application
B
loaded in memory, deamon or webserver
unit tested
unit tested
not unit tested
http://teotti.com/create-dependency-structures-with-local-ruby-gems#gotcha-flaky-bugs-caused-by-missing-requirement-statements

67. team
diligence

68. A
C
D
B
E
main Ruby application
your health plan
API
drug information
claims platform
product
information
persistence DB

69. A
C
D
B
E
main Ruby application
F
H
I L
modular monolith!
membership
payment API
payment
platform
bank
transaction
credit card
transaction
your health plan
API
drug information
claims platform
product
information
persistence DDB

70. A
C
D
B
E
main Ruby application
F
H
I L
payment
platform

72. A
C
D
B
E
main Ruby application
F
H
I L
your health plan
API
DDB

73. A
C
D
B
E
main Ruby application
F
H
I L
membership
payment API
DDB

74. A
C
D
B
E
main Ruby application
F
H
I LDDB

75. A
C
D
B
E
main Ruby application
F
H
I LDDB

76. A
C
D
B
E
main Ruby application
F
H
I LDDB

77. A
C
D
B
E
main Ruby application
F
H
I L
I find your use of
Gems disturbing
Do I really look like
a guy with a plan?
*nods then
deletes your
Gem*
DDB

78. Director of security
Director of happiness
Director of project Death Star

79. team
diligence

80. http://blog.codinghorror.com/the-last-responsible-moment/
team
diligence

81. http://teotti.com/rails-service-oriented-architecture-alternative-with-components/
to be continued…
premature use of SOA in a small team

82. A
C
D
B
E
main Ruby application
F
H
I L
membership
payment API
payment
platform
bank
transaction
credit card
transaction
your health plan
API
drug information
claims platform
product
information
persistence DDB

83. main Ruby application
your health
plan API
drug
information
claims
platform
product
information
persistence
membership
payment
API
payment
platform
bank
transaction
credit card
transaction
DB

84. deploy parts of a monolith
http://teotti.com/deploy-parts-of-a-ruby-on-rails-application/

85. monolithic Ruby application
DB

86. editorial admin
persistence
site search
componentized Ruby application
public content
shared ui
DB

87. editorial admin
persistence
site search
componentized Ruby application
public content ui
shared ui
DB
Persistence::ContentPieceRepository.create(params)

88. editorial admin
persistence
site search
componentized Ruby application
public content
shared ui
DB

89. editorial admin
persistence
site search
componentized Ruby application
public content
shared ui
DB

90. editorial admin ui
persistence
site search
componentized Ruby application
public content
shared ui
DB
Persistence::ContentPieceRepository.find_by_slug('/article-slug')

91. deploy@adminServer $ RUNNING_MODE=admin puma

92. editorial admin
persistence
site search
Rails application
public content
shared ui
DB

93. deploy@publicServer $ RUNNING_MODE=public puma

94. editorial admin
persistence
site search
componentized Ruby application
public content
shared ui
DB

95. editorial admin
persistence
site search
componentized Ruby application
public content
shared ui
DB

96. legacy migration

97. editorial admin ui
persistence
site search
componentized Ruby application
public content ui
shared ui
DB
legacy
migration
AWS
SQS
massage and
transform content
legacy system
pull legacy
content

99. automated
testing
team
diligence
local Ruby
gems

100. automated
testing
team
diligence
local Ruby
gems
team
in a
fixed
mindset

101. gems require a bit of experience,
gems require you to work a bit hard,
this person doesn’t write maintainable code yet,
that person doesn’t understand ruby gems yet
gems require talented developers
gems are only for smart developers,
this person always write unmaintainable code,
that person will never understand ruby gems
https://www.youtube.com/watch?v=W47rcJowx7k
http://www.amazon.com/Mindset-The-New-Psychology-Success/dp/0345472322

102. automated
testing
team
diligence
local Ruby
gems

103. automated
testing
team
diligence
local Ruby
gems

104. automated
testing
team
diligence
local Ruby
gems

105. @agenteo
Enrico Teotti
http://teotti.com
www.slideshare.net/agenteo

106. More Links
https://leanpub.com/cbra
http://teotti.com/component-based-rails-architecture-primer/
http://teotti.com/reengineer-legacy-rails-applications/