The Even Darker Art of Rails Engines

Given at RailsConf 2009

Transcript

1. The
   Even-Darker Art
   of
   Rails Engines
   

   View Slide

2. @lazyatom
   

   View Slide

3. github.com/lazyatom/engines
   

   View Slide

4. Rails 2.3
   

   View Slide

5. history
   

   View Slide

6. November 2005
   

   View Slide

7. it’s distracting!
   

   View Slide

8. reuse is overrated!
   

   View Slide

9. Evil! Evil!
   Evil!
   Evil!
   Evil!
   Evil!
   Evil!
   Evil! Shit!
   

   View Slide

10. eek!
    

    View Slide

11. appable_plugins
    

    View Slide

12. desert
    

    View Slide

13. merb slices?
    

    View Slide

14. View Slide

15. engines
    

    View Slide

16. !"#$%&!"#$'#(%&$#)&!"#$%&*$+,#-.!)
    !"#$%&'()
    $$*%&'()$++,$-'%!.%&'()./0#'12%)/'0
    "0!
    3$405/0"6$%1"$7-(5/06$8/)9$%0$%77:$!/1";)'1<=
    !"#$"05/0">
    $$9%6.%77.!/1";)'1<>
    "0!
    3$?")(106$)1("$/#$)9"$"05/0"$69/76$8/)9$%$1'()/05$#/-"
    !"#$1'()"!>
    $$@/-"="A/6)>B1'()/05.#/-"C
    "0!
    !"#$D/"8.7%)9
    $$@/-"=E'/0B!/1";)'1"0!
    

    View Slide

17. app/controllers/
    models/
    helpers/
    views/
    metal/
    

    View Slide

18. *$+,#-&"**&23-'!3$$(!&*$+,#-523-'!3$$(!.!)
    ;-%66$H-(5/0I'0)1'--"1/0/1**$#2"'#3-43-'!3$$(!
    $$!"#$/0!"A
    $$$$1"0!"1$J)"A)$,K$LM"--'F$H-(5/0NL
    $$"0!
    "0!
    

    View Slide

19. 9"-7"1$J%--
    won’t load from your plugin
    

    View Slide

20. Ticket #1905
    

    View Slide

21. config/routes.rb
    

    View Slide

22. O;)/'0I'0)1'--"1JJ?'()/05JJ?'()"6=!1%8$!'$+2%7+
    $$2%7=;'00";)$G:7%)9GF$J;'0)1'--"1$,K$L7-(5/0LF$
    $$$$$$$$$$$$$$$$$$$$$$$J%;)/'0$,K$L/0!"AL
    "0!
    *$+,#-&23-6#,&!3+'(%.!)
    

    View Slide

23. top precedence
    

    View Slide

24. O;)/'0I'0)1'--"1JJ?'()/05JJ?'()"6=!1%8$!'$+2%7+
    $$2%7=;'00";)$G:7%)9GF$J;'0)1'--"1$,K$L7-(5/0LF$
    $$$$$$$$$$$$$$$$$$$$$$$J%;)/'0$,K$L/0!"AL
    "0!
    O;)/'0I'0)1'--"1JJ?'()/05JJ?'()"6=!1%8$!'$+2%7+
    $$3$===$')9"1$1'()"6$===
    $$2%7=;'00";)$G:7%)9GF$J;'0)1'--"1$,K$L%77LF$
    $$$$$$$$$$$$$$$$$$$$$$$J%;)/'0$,K$L/0!"AL
    $$3$===$')9"1$1'()"6$===
    "0!
    in your plugin:
    in your app:
    

    View Slide

25. O;)/'0I'0)1'--"1JJ?'()/05JJ?'()"6=!1%8$!'$+2%7+
    $$2%7=;'00";)$G:7%)9GF$J;'0)1'--"1$,K$L7-(5/0LF$
    $$$$$$$$$$$$$$$$$$$$$$$J%;)/'0$,K$L/0!"AL
    "0!
    O;)/'0I'0)1'--"1JJ?'()/05JJ?'()"6=!1%8$!'$+2%7+
    $$3$===$')9"1$1'()"6$===
    $$2%7=;'00";)$G:7%)9GF$J;'0)1'--"1$,K$L%77LF$
    $$$$$$$$$$$$$$$$$$$$$$$J%;)/'0$,K$L/0!"AL
    $$3$===$')9"1$1'()"6$===
    "0!
    in your plugin:
    in your app:
    

    View Slide

26. Ticket #2592
    (also Ticket #329)
    

    View Slide

27. 785*$+,#-&$#)&785*$+,#-.!)
    2'!(-"$P$$!"#$6"-#=%!!.1'()"6B7"*C
    $$$$2%7=;'00";)$L:6)(##LF$J;'0)1'--"1$,K$L)9/056L
    $$"0!
    "0!
    O;)/'0I'0)1'--"1JJ?'()/05JJ?'()"6=!1%8$!'$+2%7+
    $$3$<'(1$%77$1'()"6===
    $$P$$3$");===
    "0!
    

    View Slide

28. what’s missing?
    

    View Slide

29. public assets
    

    View Slide

30. copy
    

    View Slide

31. file clash
    

    View Slide

32. 83+!5*$+,#--%'"$$.!)
    2<./2%5"6$,$H%)90%2"=0"8B@/-"=!/10%2"B..@QR4..CC$S$
    $$$$$$$$$$$$$$L%66")6:/2%5"6L
    )%15")$,$?%/-6=1'')$S$L7(&-/;:/2%5"6:2<.7-(5/0L
    @/-"T)/-6=2U!/1.7B)%15")C
    2<./2%5"6=;9/-!1"0="%;9$!'$+"+$
    $$$$@/-"T)/-6=;7.1B"F$)%15")$S$"=&%6"0%2"C$
    "0!
    

    View Slide

33. 83+!5*$+,#--%'"$$.!)
    2<./2%5"6$,$H%)90%2"=0"8B@/-"=!/10%2"B..@QR4..CC$S$
    $$$$$$$$$$$$$$L%66")6:/2%5"6L
    )%15")$,$?%/-6=1'')$S$L7(&-/;:/2%5"6:2<.7-(5/0L
    )%15")=2%U".6<2-/0UB2<./2%5"6C$(0-"66$)%15")="A/6)>
    

    View Slide

34. migrations
    

    View Slide

35. simple DSL
    

    View Slide

36. rollback
    

    View Slide

37. !&:2/51%)":
    $$VWWXWYWYYVYVZ[.%-79%=1&
    version
    20090101121234
    20090102142345
    2008123123456
    VWWXWYWVY[VZ[\.&")%=1&
    7-(5/0:!&:2/51%)":
    $$VWW]YVZYZ[\^.5%22%=1&
    

    View Slide

38. version
    20090101121234
    20090102142345
    2008123123456
    1%U"$!&J1'--&%;U
    P/51%)'1=1'--&%;U
    P/51%)'13;(11"0).D"16/'0
    P/51%)'132/51%)"!=-%6)
    P/51%)'1=5").%--.D"16/'06
    BL_4R4I`$D"16/'0$@?aP$
    $
    $
    $$6;9"2%.2/51%)/'06LC
    =2%7BbJ)'./C=6'1)
    

    View Slide

39. it gets worse
    

    View Slide

40. !&:2/51%)":
    $$WWY.%-79%=1&
    version
    001
    002
    WWV.&")%=1&
    7-(5/0:!&:2/51%)":
    $$WWY.5%22%=1&
    

    View Slide

41. http://www.flickr.com/photos/bk2204/475332962/
    

    View Slide

42. single timeline
    

    View Slide

43. app migration 1
    app migration 2
    plugin migration 1
    app migration 3
    plugin migra
    install
    upgrade
    You
    Me
    

    View Slide

44. app migration 1
    app migration 2
    plugin migration 1
    app migration 3
    plugin migration 2
    You
    

    View Slide

45. WW[.!"-)%=1&
    !&:2/51%)":
    $$WWY.%-79%=1&
    WWV.&")%=1&
    7-(5/0:!&:2/51%)":
    $$WWY.5%22%=1&
    WWZ.7-(5/0.)'.WWY=1&
    

    View Slide

46. WW[.!"-)%=1&
    !&:2/51%)":
    $$WWY.%-79%=1&
    WWV.&")%=1&
    7-(5/0:!&:2/51%)":
    $$WWY.5%22%=1&
    WWZ.7-(5/0.)'.WWY=1&
    Copy &
    Retimestamp?
    Reference?
    Symlink?
    

    View Slide

47. Ticket #2058
    interblah.net/plugin-migrations
    

    View Slide

48. my recommendation?
    (for the moment, at least)
    

    View Slide

49. write a generator
    c$6;1/7):5"0"1%)"$%;)6.%6.#(.2/51%)/'06
    $$$$
    $$$"A/6)6$$!&:2/51%)"
    $$$;1"%)"$$!&:2/51%)":VWWXW\W\YYYZZd.&-%9=1&
    c$===
    (within your plugin)
    

    View Slide

50. techniques
    

    View Slide

51. overriding functionality
    

    View Slide

52. views just work
    

    View Slide

53. controllers
    

    View Slide

54. straight override
    

    View Slide

55. View Slide

56. View Slide

57. module
    

    View Slide

58. View Slide

59. View Slide

60. View Slide

61. namespaced
    

    View Slide

62. View Slide

63. View Slide

64. View Slide

65. playing nice with the
    class cache
    

    View Slide

66. 1/23*8/36/1**$#2"'#3-43-'!3$$(!/
    9"%/)((-/!(73:(;/6!37/'9(/73;+$(/
    '!((/)+'/#%/%'#$$/"2'#:(<<
    <
    <
    <
    <
    <
    <
    !
    

    View Slide

67. O;)/D"_(77'1)JJe"7"0!"0;/"6=-'%!.'0;".7%)96
    

    View Slide

68. ApplicationController
    AppController PluginController
    

    View Slide

69. ApplicationController
    PluginController
    

    View Slide

70. 23-6#,&(-:#!3-7(-'.!)
    ?%/-6JJQ0/)/%-/f"1=1(0$!'$+;'0#/5+
    $$3$");===
    $$;'0#/5=1"-'%!.7-(5/06$,$)1("
    $$
    "0!
    

    View Slide

71. 83+!5*$+,#-&"**&23-'!3$$(!%&,33;523-'!3$$(!.!)
    ;-%66$g''!I'0)1'--"1$h$===
    $$(0-'%!%&-"
    $$
    $$3$");$===
    "0!
    

    View Slide

72. init.rb woes
    

    View Slide

73. ;'0#/5=)'.71"7%1"$!'
    $$
    "0!
    785*$+,#--#'.!)
    $$_'2"O77I-%66="A)"0!BP

    View Slide

74. testing
    

    View Slide

75. ApplicationController
    PluginController
    AppController
    

    View Slide

76. ApplicationController
    PluginController
    Their Code
    Your Code
    

    View Slide

77. View Slide

78. !
    "
    #
    $
    

    View Slide

79. View Slide

80. unit test?
    

    View Slide

81. test in your own rails
    environment?
    

    View Slide

82. plugin_test_helper
    

    View Slide

83. I care about testing
    my chunk
    

    View Slide

84. You care about testing
    your whole app
    

    View Slide

85. empower the
    developer
    

    View Slide

86. avoiding fail
    

    View Slide

87. ;%6"$;'!"=;'06(2"1
    $$89"0$;'!"=%()9'1
    $$$$1"(6"=2'6)-<$,j$:"##";)/D":
    $$89"0$1%0!B!"D"-'7"1C
    $$$$1"(6"=)1/;U/"1.&().7'66/&-"B)1("C
    $$"-6"
    $$$$1"(6"='D"11%)"!N
    "0!
    

    View Slide

88. consume wisely
    

    View Slide

89. Serving Size 14 kloc
    Nutrition Facts
    Amount Per Serving 1 bad engine
    Calories 10,666
    Long Methods 1578g 34%
    God Objects 326g 7%
    Stress 320mg 119%
    Total Fat 2674g 98%
    Hairloss 45g 45.8%
    % Daily Value*
    Technical Debt 13g 87%
    Untested Code 1578mg 34%
    Hidden Bugs 326mg 7%
    Benefit 1mg 0.1%
    

    View Slide

90. you will not be able to
    write some engines.
    

    View Slide

91. you will not be able to
    use some engines.
    

    View Slide

92. extract
    specific functionality
    

    View Slide

93. establish some
    clear integration points
    

    View Slide

94. you are customer #1
    

    View Slide

95. READ the CODE
    

    View Slide

96. james@lazyatom.com
    lets@gofreerange.com
    FIN
    

    View Slide