Middleware: A General Purpose Abstraction

1. Middleware A general abstraction.
2. Mitchell Hashimoto @mitchellh
6. Large Classes
7. Large Classes
8. Large Classes
9. Large Classes
10. Large Classes
11. Large Classes
12. Problems:
13. 1. Unapproachable
14. 2. Unclear dependencies
15. 3. Difficult to Test
16. Mixin all the things!
17. 1 module Authlogic 2 module Session # :nodoc: 3 # This is the base class Authlogic, where all modules are included. 4 # 5 class Base 6 include Foundation 7 include Callbacks 8 9 # Included first so that the session resets itself to nil 10 include Timeout 11 12 # Included in a specific order so they are tried in this order when persisting 13 include Params 14 include Cookies 15 include Session 16 include HttpAuth 17 18 # Included in a specific order so magic states gets ran after a record is found 19 include Password 20 include UnauthorizedRecord 21 include MagicStates 22 23 include Activation 24 include ActiveRecordTrickery 25 include BruteForceProtection 26 include Existence 27 include Klass 28 include MagicColumns 29 include PerishableToken 30 include Persistence 31 include Scopes 32 include Id 33 include Validation 34 include PriorityRecord 35 end 36 end 37 end
18. Function Composition F*** Yeah.
19. 1 def f(value) 2 value + 1 3 end 4 5 def g(value) 6 value * 2 7 end
20. 1 f(g(1)) # => 3 2 3 g(f(1)) # => 4
21. 1 f(g(1)) # => 3 2 3 g(f(1)) # => 4 Clear Ordering
22. 1 f(g(1)) # => 3 2 3 g(f(1)) # => 4 Clear Dependencies
23. 1 f(g(1)) # => 3 2 3 g(f(1)) # => 4 Easy to Test
24. 1 f(g(1)) # => 3 2 3 g(f(1)) # => 4 True Separation of Logic
25. Function Composition Applied to Large Classes?
26. Middleware
27. Rack Middleware
28. Python Web Server Gateway Interface v1.0 python.org/dev/peps/pep-0333/
29. Request Processing
30. 1 app = Rack::Builder.new do 2 use Middleware::Example 3 use Rack::CommonLogger 4 use Rack::ShowExceptions 5 end
31. 1 app = Rack::Builder.new do 2 use Middleware::Example 3 use Rack::CommonLogger 4 use Rack::ShowExceptions 5 end
32. 1 app = Rack::Builder.new do 2 use Middleware::Example 3 use Rack::CommonLogger 4 use Rack::ShowExceptions 5 end
33. 1 module Middleware 2 class Example 3 def initialize(app) 4 @app = app 5 end 6 7 def call(env) 8 # do something before the next middleware 9 # possibly modify the environment 10 11 # run the next middleware in the stack 12 @app.call(env) 13 14 # do something after the next middleware 15 end 16 end 17 end
34. 1 module Middleware 2 class Example 3 def initialize(app) 4 @app = app 5 end 6 7 def call(env) 8 # do something before the next middleware 9 # possibly modify the environment 10 11 # run the next middleware in the stack 12 @app.call(env) 13 14 # do something after the next middleware 15 end 16 end 17 end
35. 1 module Middleware 2 class Example 3 def initialize(app) 4 @app = app 5 end 6 7 def call(env) 8 # do something before the next middleware 9 # possibly modify the environment 10 11 # run the next middleware in the stack 12 @app.call(env) 13 14 # do something after the next middleware 15 end 16 end 17 end
36. 1 module Middleware 2 class Example 3 def initialize(app) 4 @app = app 5 end 6 7 def call(env) 8 # do something before the next middleware 9 # possibly modify the environment 10 11 # run the next middleware in the stack 12 @app.call(env) 13 14 # do something after the next middleware 15 end 16 end 17 end
37. 1 app = Rack::Builder.new do 2 use Middleware::Example 3 use Rack::CommonLogger 4 use Rack::ShowExceptions 5 end
38. Why is middleware so amazing?
39. Explicit Ordering
40. 1 app = Rack::Builder.new do 2 use Middleware::Example 3 use Rack::CommonLogger 4 use Rack::ShowExceptions 5 end
41. Visible Dependencies
42. 1 module Middleware 2 class Example 3 # ... 4 5 def call(env) 6 if env["path"] == "/foo" 7 env["path"] = "/bar" 8 end 9 10 @app.call(env) 11 end 12 end 13 end
43. 1 module Middleware 2 class Example 3 # ... 4 5 def call(env) 6 if env["path"] == "/foo" 7 env["path"] = "/bar" 8 end 9 10 @app.call(env) 11 end 12 end 13 end
44. Easily Tested
45. 1 module Middleware 2 class Example 3 # ... 4 5 def call(env) 6 if env["path"] == "/foo" 7 env["path"] = "/bar" 8 end 9 10 @app.call(env) 11 end 12 end 13 end
46. 1 state = { "path" => "/foo" } 2 m = Middleware::Example.new 3 m.call(state) 4 assert state["path"] == "/bar"
47. Extensible: Subclass!
48. Vagrant vagrantup.com
49. Virtual Machine Lifecycle
50. $ vagrant suspend
51. 1 Builder.new do 2 use General::CheckVirtualbox 3 use General::Validate 4 use VM::CheckAccessible 5 use VM::Suspend 6 end
52. 1 Builder.new do 2 use General::CheckVirtualbox 3 use General::Validate 4 use VM::CheckAccessible 5 use VM::Suspend 6 end
53. 1 Builder.new do 2 use General::CheckVirtualbox 3 use General::Validate 4 use VM::CheckAccessible 5 use VM::Suspend 6 end
54. 1 module Vagrant::Action::General 2 class Validate 3 # ... 4 5 def call(env) 6 if env[:validate] 7 env[:vm].config.validate!(env[:vm].env) 8 end 9 10 @app.call(env) 11 end 12 end 13 end
55. 1 module Vagrant::Action::General 2 class Validate 3 # ... 4 5 def call(env) 6 if env[:validate] 7 env[:vm].config.validate!(env[:vm].env) 8 end 9 10 @app.call(env) 11 end 12 end 13 end
56. 1 module Vagrant::Action::General 2 class Validate 3 # ... 4 5 def call(env) 6 if env[:validate] 7 env[:vm].config.validate!(env[:vm].env) 8 end 9 10 @app.call(env) 11 end 12 end 13 end
57. 1 module Vagrant::Action::General 2 class Validate 3 # ... 4 5 def call(env) 6 if env[:validate] 7 env[:vm].config.validate!(env[:vm].env) 8 end 9 10 @app.call(env) 11 end 12 end 13 end
58. 1 Builder.new do 2 use General::CheckVirtualbox 3 use General::Validate 4 use VM::CheckAccessible 5 use VM::Suspend 6 end
59. 1 module Vagrant::Action::VM 2 class Suspend 3 # ... 4 5 def call(env) 6 if env[:vm].state == :running 7 env[:vm].driver.suspend 8 end 9 10 @app.call(env) 11 end 12 end 13 end
60. $ vagrant up
61. 1 Builder.new do 2 use General::CheckVirtualbox 3 use General::Validate 4 use VM::CheckAccessible 5 use VM::CheckBox 6 use VM::Import 7 use VM::CheckGuestAdditions 8 use VM::DefaultName 9 use VM::MatchMACAddress 10 use VM::CleanMachineFolder 11 use VM::ClearForwardedPorts 12 use VM::CheckPortCollisions 13 use VM::ForwardPorts 14 use VM::Provision 15 use VM::PruneNFSExports 16 use VM::NFS 17 use VM::ClearSharedFolders 18 use VM::ShareFolders 19 use VM::HostName 20 use VM::ClearNetworkInterfaces 21 use VM::Network 22 use VM::Customize 23 use VM::Boot 24 end
62. 1 Builder.new do 2 use General::CheckVirtualbox 3 use General::Validate 4 use VM::CheckAccessible 5 use VM::CheckBox 6 use VM::Import 7 use VM::CheckGuestAdditions 8 use VM::DefaultName 9 use VM::MatchMACAddress 10 use VM::CleanMachineFolder 11 use VM::ClearForwardedPorts 12 use VM::CheckPortCollisions 13 use VM::ForwardPorts 14 use VM::Provision 15 use VM::PruneNFSExports 16 use VM::NFS 17 use VM::ClearSharedFolders 18 use VM::ShareFolders 19 use VM::HostName 20 use VM::ClearNetworkInterfaces 21 use VM::Network 22 use VM::Customize 23 use VM::Boot 24 end
63. Scared?
64. Real Example
65. Diaspora user.rb
66. 1 def accept_invitation!(opts = {}) 2 if self.invited? 3 self.setup(opts) 4 self.invitation_token = nil 5 self.password = opts[:password] 6 self.password_confirmation = opts[:password_confirmation] 7 8 self.save 9 return unless self.errors.empty? 10 11 # moved old Invitation#share_with! logic into here, 12 # but i don't think we want to destroy the invitation 13 # anymore. we may want to just call self.share_with 14 invitations_to_me.each do |invitation| 15 if !invitation.admin? && invitation.sender.share_with(self.person, invitation.aspect) 16 invitation.destroy 17 end 18 end 19 20 self 21 end 22 end
67. 1 def accept_invitation!(opts = {}) 2 if self.invited? 3 self.setup(opts) 4 self.invitation_token = nil 5 self.password = opts[:password] 6 self.password_confirmation = opts[:password_confirmation] 7 8 self.save 9 return unless self.errors.empty? 10 11 # moved old Invitation#share_with! logic into here, 12 # but i don't think we want to destroy the invitation 13 # anymore. we may want to just call self.share_with 14 invitations_to_me.each do |invitation| 15 if !invitation.admin? && invitation.sender.share_with(self.person, invitation.aspect) 16 invitation.destroy 17 end 18 end 19 20 self 21 end 22 end
68. 1 def accept_invitation!(opts = {}) 2 if self.invited? 3 self.setup(opts) 4 self.invitation_token = nil 5 self.password = opts[:password] 6 self.password_confirmation = opts[:password_confirmation] 7 8 self.save 9 return unless self.errors.empty? 10 11 # moved old Invitation#share_with! logic into here, 12 # but i don't think we want to destroy the invitation 13 # anymore. we may want to just call self.share_with 14 invitations_to_me.each do |invitation| 15 if !invitation.admin? && invitation.sender.share_with(self.person, invitation.aspect) 16 invitation.destroy 17 end 18 end 19 20 self 21 end 22 end
69. 1 def accept_invitation!(opts = {}) 2 if self.invited? 3 self.setup(opts) 4 self.invitation_token = nil 5 self.password = opts[:password] 6 self.password_confirmation = opts[:password_confirmation] 7 8 self.save 9 return unless self.errors.empty? 10 11 # moved old Invitation#share_with! logic into here, 12 # but i don't think we want to destroy the invitation 13 # anymore. we may want to just call self.share_with 14 invitations_to_me.each do |invitation| 15 if !invitation.admin? && invitation.sender.share_with(self.person, invitation.aspect) 16 invitation.destroy 17 end 18 end 19 20 self 21 end 22 end
70. 1 def accept_invitation!(opts = {}) 2 if self.invited? 3 self.setup(opts) 4 self.invitation_token = nil 5 self.password = opts[:password] 6 self.password_confirmation = opts[:password_confirmation] 7 8 self.save 9 return unless self.errors.empty? 10 11 # moved old Invitation#share_with! logic into here, 12 # but i don't think we want to destroy the invitation 13 # anymore. we may want to just call self.share_with 14 invitations_to_me.each do |invitation| 15 if !invitation.admin? && invitation.sender.share_with(self.person, invitation.aspect) 16 invitation.destroy 17 end 18 end 19 20 self 21 end 22 end
71. 1 def accept_invitation!(opts = {}) 2 if self.invited? 3 self.setup(opts) 4 self.invitation_token = nil 5 self.password = opts[:password] 6 self.password_confirmation = opts[:password_confirmation] 7 8 self.save 9 return unless self.errors.empty? 10 11 # moved old Invitation#share_with! logic into here, 12 # but i don't think we want to destroy the invitation 13 # anymore. we may want to just call self.share_with 14 invitations_to_me.each do |invitation| 15 if !invitation.admin? && invitation.sender.share_with(self.person, invitation.aspect) 16 invitation.destroy 17 end 18 end 19 20 self 21 end 22 end
72. 1 def setup(opts) 2 self.username = opts[:username] 3 self.email = opts[:email] 4 self.language = opts[:language] 5 self.language ||= I18n.locale.to_s 6 self.valid? 7 errors = self.errors 8 errors.delete :person 9 return if errors.size > 0 10 self.set_person(Person.new(opts[:person] || {} )) 11 self.generate_keys 12 self 13 end
73. 1 class SetupUser 2 def call(env) 3 user = env[:user] 4 5 user.username = env[:username] 6 user.email = env[:email] 7 user.language = env[:language] 8 user.language ||= I18n.locale.to_s 9 user.valid? 10 errors = user.errors 11 errors.delete :person 12 raise ErrorsHappened if errors.size > 0 13 user.set_person(Person.new(env[:person] || {} )) 14 user.generate_keys 15 end 16 end
74. 1 class SetupUser 2 def call(env) 3 user = env[:user] 4 5 user.username = env[:username] 6 user.email = env[:email] 7 user.language = env[:language] 8 user.language ||= I18n.locale.to_s 9 user.valid? 10 errors = user.errors 11 errors.delete :person 12 raise ErrorsHappened if errors.size > 0 13 user.set_person(Person.new(env[:person] || {} )) 14 user.generate_keys 15 @app.call(env) 16 end 17 end
75. 1 class SetupUser 2 def call(env) 3 user = env[:user] 4 5 user.username = env[:username] 6 user.email = env[:email] 7 user.language = env[:language] 8 user.language ||= I18n.locale.to_s 9 user.valid? 10 errors = user.errors 11 errors.delete :person 12 raise ErrorsHappened if errors.size > 0 13 user.set_person(Person.new(env[:person] || {} )) 14 user.generate_keys 15 @app.call(env) 16 end 17 end
76. 1 Builder.new do 2 use HaltIfInvited 3 use SetupUser 4 use SetPassword 5 use ClearInvitations 6 end
77. 1 def accept_invitation!(opts={}) 2 run(:accept_invitation, opts.merge(:user => self)) 3 end
78. When and Where
79. Reuse
80. 1 Builder.new do 2 use SetupUser 3 use AcceptInvite 4 use ConfirmationEmail 5 end 6 7 Builder.new do 8 use SetupUser 9 use Signup 10 end
81. 1 Builder.new do 2 use SetupUser 3 use AcceptInvite 4 use ConfirmationEmail 5 end 6 7 Builder.new do 8 use SetupUser 9 use Signup 10 end
82. Serial Invocations
83. 1 def do_something! 2 foo(1) 3 bar(2) 4 baz(3) 5 end 6 7 Builder.new do 8 use Foo, 1 9 use Bar, 2 10 use Baz, 3 11 end
84. Composition
85. 1 def do_something! 2 foo(bar(baz(1))) 3 end 4 5 Builder.new { 6 use Baz 7 use Bar 8 use Foo 9 }.call(1)
86. Mitchell Hashimoto @mitchellh THANKS!