Keeping Software Soft

Software provides continual value when it can evolve with the business. But without proper care it's easy for software to become rigid and difficult to change--it stops being soft. In this talk John introduces ways to think of software as independent, replaceable components.

Transcript

1. Keeping Software Soft
   John Kary
   @johnkary
   Lawrence Coders, January 2015
   

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2. Hardware
   

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3. Software
   

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4. Program
   

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5. Program
   Data In
   

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6. Program
   Data In Data Out
   

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7. Program
   Program Program
   

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8. $ ls -l | grep "b"
   fabien.txt
   rabid-bear.rb
   sunk-cost.bl
   zabbazabba.do
   !
   !
   $ tail -f logs/prod.log | grep "error"
   [2015-01-16 21:15:45] app.error — Uncaught Exception
   [2015-01-16 23:22:42] app.error — Invalid argument "1" expected "2"
   [2015-01-17 00:01:52] app.error — SQL parse error "); DROP TABLE St
   

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9. $ ls -l | grep "b"
   fabien.txt
   rabid-bear.rb
   sunk-cost.bl
   zabbazabba.do
   !
   !
   $ tail -f logs/prod.log | grep "error"
   [2015-01-16 21:15:45] app.error — Uncaught Exception
   [2015-01-16 23:22:42] app.error — Invalid argument "1" expected "2"
   [2015-01-17 00:01:52] app.error — SQL parse error "); DROP TABLE St
   Unix Pipes
   

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10. https://www.flickr.com/photos/billybrown00/4982722491
    

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11. http://www.xcalak.info/images/misc/voip_network_l.gif
    

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12. http://www.xcalak.info/images/misc/voip_network_l.gif
    +1 785-979-8176
    

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14. GET /index.html HTTP/1.1
    Host: www.lmgtfy.com
    

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15. GET /index.html HTTP/1.1
    Host: www.lmgtfy.com
    www.lmgtfy.com
    

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16. GET /index.html HTTP/1.1
    Host: www.lmgtfy.com
    www.lmgtfy.com
    HTTP/1.1 200 OK
    Date: Mon, 23 May 2005 22:38:34 GMT
    Last-Modified: Wed, 08 Jan 2003 23:11:55 GMT
    ETag: "3f80f-1b6-3e1cb03b"
    Content-Type: text/html; charset=UTF-8
    !
    An Example Page
    Hello World
    

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17. RFC2616
    

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18. RFC2616
    http://www.w3.org/Protocols/rfc2616/rfc2616-sec4.html#sec4
    4. HTTP Message
    

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19. Program
    Message
    Protocol
    

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20. Program
    Message
    Protocol
    Interface
    

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21. Interface
    "[Prohibits] access to all resources by default,
    allowing access only through well-defined entry points"
    http://en.wikipedia.org/wiki/Interface_(computing)
    "[A] shared boundary across which two separate components
    of a computer system exchange information."
    

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25. https://www.flickr.com/photos/dominicotine/7187354723
    

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26. https://www.flickr.com/photos/toasty/330752049
    

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27. https://www.flickr.com/photos/brilliantmichael/4172218074
    

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28. http://www.flickr.com/photos/amcgore/5518551326/
    

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29. https://www.flickr.com/photos/charlesonflickr/362975740
    

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30. Program
    Processing
    Program
    Program
    Program
    Your Thing
    Message Boundary
    Their Thing
    You Don't Know
    

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31. Server
    

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32. Server
    Processes
    

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33. Server
    Processes
    

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34. Server
    Processes
    Packages
    

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35. Server
    Processes
    Packages
    Classes
    

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36. Server
    Processes
    Packages
    Classes
    Functions
    

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37. Server
    Processes
    Packages
    Classes
    Functions
    

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38. Server
    Processes
    Packages
    Classes
    Functions
    

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39. Server
    Processes
    Packages
    Classes
    Functions
    

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40. Server
    Processes
    Packages
    Classes
    Functions
    

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41. Server
    Processes
    Packages
    Classes
    Functions
    

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42. Server
    Processes
    Packages
    Classes
    Functions
    Network IO
    

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45. Your Package
    Not
    Your
    Package
    

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46. Your Package
    Not
    Your
    Package
    

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47. Program
    Message
    Protocol
    

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48. Program
    Message
    Protocol
    Interface
    

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49. Program
    Message
    Protocol
    Interface
    Adapter
    

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50. Message Passing
    Between Processes
    ls grep
    Keyboard
    STDIN
    Terminal
    STDOUT
    C C
    

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51. Message Passing
    Between Processes
    ls grep
    Keyboard
    STDIN
    Terminal
    STDOUT
    C C
    

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52. Message Passing
    Between Processes
    ls grep
    Keyboard
    STDIN
    Terminal
    STDOUT
    C C
    

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53. Further Study
    Basic of the Unix Philosophy!
    http://www.catb.org/esr/writings/taoup/html/ch01s06.html
    The Art of Unix Programming (2003)
    !
    The Art of Destroying Software!
    Talk by Greg Young (Unsure location/date)
    http://vimeo.com/108441214
    !
    Stop Writing Classes!
    Jack Diederich @ PyCon 2012
    https://www.youtube.com/watch?v=o9pEzgHorH0
    !
    Architecture the Lost Years
    Robert C Martin (Uncle Bob) @ Ruby Midwest 2011
    http://confreaks.com/videos/759-rubymidwest2011-keynote-architecture-the-lost-years
    !
    Seven Languages in Seven Weeks (Erlang chapter)!
    https://pragprog.com/book/btlang/seven-languages-in-seven-weeks
    

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54. Homework
    • Build small things
    • Build simple things and compose them together
    • Connect things by generic messages
    • Isolate complexity into more small things
    • Build things that can be thrown away
    

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55. fin
    http://johnkary.net/talks
    @johnkary
    

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