Middleware: A General Purpose Abstraction

Transcript

1. Middleware A general abstraction.

2. Mitchell Hashimoto @mitchellh

3. None
4. None
5. None

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!