The Lifecycle of a Rails Response

This breathtaking documentary series combines rare action, unimaginable scale, impossible locations and intimate moments captured from the deepest depths of Rails internals. Last year, we followed the lifecycle of best loved, wildest and most elusive Rails components through a request, from the browser to a controller action. This year, our journey takes us across the great text/plain, following the flow of HTTP streams, taking in the spectacular Action View as we find our way back to the browser. Join us to unearth the amazing lifecycle of a Rails response.

Transcript

1. INSIDE RAILS
   The Lifecycle of a Response
   

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2. View Slide

3. View Slide

4. https://skylight.io/r/railsconf
   Don’t struggle to learn why your app is slow.
   Get answers with Skylight.
   DO THE
   ANSWER DANCE.
   SKYLIGHT
   

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5. View Slide

6. View Slide

7. View Slide

8. app/controllers/hello_controller.rb
   Terminal
   $
   Trying 34.194.84.73...
   Connected to ec2-34-194-84-73.compute-1.amazonaws.com.
   Escape character is ‘^]’.
   >
   telnet 34.194.84.73 80
   Picture: Masai Mara Wildlife / Matt Scobel / CC BY 3.0
   

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9. app/controllers/hello_controller.rb
   class SafariController < ActionController::Base
   def hello
   # ...do stuff here...
   render plain: 'Hello World'
   end
   end
   app/controllers/safari_controller.rb
   app/controllers/hello_controller.rb
   Terminal
   $
   Trying 34.194.84.73...
   Connected to ec2-34-194-84-73.compute-1.amazonaws.com.
   Escape character is ‘^]’.
   >
   telnet 34.194.84.73 80
   GET /safari HTTP/1.1
   > Host: skylight.io
   >
   Picture: Masai Mara Wildlife / Matt Scobel / CC BY 3.0
   

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10. app/controllers/hello_controller.rb
    Terminal
    $
    Trying 34.194.84.73...
    Connected to ec2-34-194-84-73.compute-1.amazonaws.com.
    Escape character is ‘^]’.
    >
    telnet 34.194.84.73 80
    GET /safari HTTP/1.1
    > Host: skylight.io
    >
    < HTTP/1.1 200 OK
    < Content-Type: text/plain
    < Content-Length: 11
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < Hello World
    app/controllers/hello_controller.rb
    class SafariController < ActionController::Base
    def hello
    # ...do stuff here...
    render plain: 'Hello World'
    end
    end
    app/controllers/safari_controller.rb
    Picture: Three Elephants in Early Morning / Yu Miyawaki / CC BY 3.0
    

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11. HELLO WORLD!
    http://skylight.io/safari
    

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12. app/controllers/hello_controller.rb
    http://skylight.io/safari
    Roar Savanna
    

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13. Ok…..?
    Hey, I have a request for you to handle.
    

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14. Sounds good.
    It’s a GET request for /safari, Host header is skylight.io
    200 OK. Content type is text/plain, body is “Roar Savanna”.
    Hey, I have a request for you to handle.
    

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15. app/controllers/hello_controller.rb
    http://skylight.io/safari
    app/controllers/hello_controller.rb
    Terminal
    $
    Trying 34.194.84.73...
    Connected to ec2-34-194-84-73.compute-1.amazonaws.com.
    Escape character is ‘^]’.
    >
    telnet 34.194.84.73 80
    

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16. app/controllers/hello_controller.rb
    http://skylight.io/safari
    app/controllers/hello_controller.rb
    Terminal
    $
    Trying 34.194.84.73...
    Connected to ec2-34-194-84-73.compute-1.amazonaws.com.
    Escape character is ‘^]’.
    >
    telnet 34.194.84.73 80
    GET /safari HTTP/1.1
    > Host: skylight.io
    >
    

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17. app/controllers/hello_controller.rb
    http://skylight.io/safari
    app/controllers/hello_controller.rb
    Terminal
    $
    Trying 34.194.84.73...
    Connected to ec2-34-194-84-73.compute-1.amazonaws.com.
    Escape character is ‘^]’.
    >
    telnet 34.194.84.73 80
    < HTTP/1.1 200 OK
    < Content-Type: text/plain
    < Content-Length: 12
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < Roar Savanna
    GET /safari HTTP/1.1
    > Host: skylight.io
    >
    Roar Savanna
    

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18. handwave handwave
    Check out last year's talk for more info!
    

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19. RACK
    

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21. app/controllers/hello_controller.rb
    http://skylight.io/safari
    app/controllers/hello_controller.rb
    env = {
    'REQUEST_METHOD' => 'GET',
    'PATH_INFO' => ‘/safari',
    'HTTP_HOST' => 'skylight.io',
    # ...
    }
    server.rb
    

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22. app/controllers/hello_controller.rb
    http://skylight.io/safari
    app/controllers/hello_controller.rb
    env = {
    'REQUEST_METHOD' => 'GET',
    'PATH_INFO' => ‘/safari',
    'HTTP_HOST' => 'skylight.io',
    # ...
    }
    app.call(env)
    server.rb
    

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23. app/controllers/hello_controller.rb
    http://skylight.io/safari
    app/controllers/hello_controller.rb
    env = {
    'REQUEST_METHOD' => 'GET',
    'PATH_INFO' => ‘/safari',
    'HTTP_HOST' => 'skylight.io',
    # ...
    }
    app.call(env)
    server.rb
    handwave handwave
    Check out last year's talk for more info!
    

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24. app/controllers/hello_controller.rb
    http://skylight.io/safari
    app/controllers/hello_controller.rb
    env = {
    'REQUEST_METHOD' => 'GET',
    'PATH_INFO' => ‘/safari',
    'HTTP_HOST' => 'skylight.io',
    # ...
    }
    app.call(env)
    server.rb
    app/controllers/hello_controller.rb
    class SafariController < ActionController::Base
    def hello
    # Get it? A savanna is a type of plain...
    render plain: 'Roar Savanna'
    end
    end
    app/controllers/safari_controller.rb
    

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25. app/controllers/hello_controller.rb
    http://skylight.io/safari
    app/controllers/hello_controller.rb
    env = {
    'REQUEST_METHOD' => 'GET',
    'PATH_INFO' => ‘/safari',
    'HTTP_HOST' => 'skylight.io',
    # ...
    }
    status, headers, body = app.call(env)
    status # => 200
    headers # => { 'Content-Type' => 'text/plain' }
    body # => [‘Roar Savanna’]
    server.rb
    1
    2
    3
    The Response Array
    

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26. app/controllers/hello_controller.rb
    http://skylight.io/safari
    Roar Savanna
    app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Content-Type: text/plain
    < Content-Length: 12
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < Roar Savanna
    

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27. app/controllers/hello_controller.rb
    http://skylight.io/safari
    Roar Savanna
    app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Content-Type: text/plain
    < Content-Length: 12
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < Roar Savanna
    

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28. View Slide

29. app/controllers/hello_controller.rb
    env = {
    'REQUEST_METHOD' => 'GET',
    'PATH_INFO' => ‘/safari',
    'HTTP_HOST' => 'skylight.io',
    # ...
    }
    status, headers, body = app.call(env)
    status # => 200
    headers # => { 'Content-Type' => 'text/plain' }
    body # => [‘Roar Savanna’]
    server.rb
    1
    The Response Array
    

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30. 1xx —
    2xx —
    3xx —
    4xx —
    5xx —
    STATUS CODES
    Informational
    Success!!
    Redirection
    Client Error
    Server Error
    

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31. Here’s a GET request for /safari, Host header is skylight.io
    OMG I DID IT! Roar Savanna!
    Huh?
    

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32. Great, I can render that.
    Here’s a GET request for /safari, Host header is skylight.io
    200 OK; Roar Savanna
    

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33. Should I index the page at /safari ?
    500 Internal Server Error
    OK, I’ll be back later!
    …
    How about now?
    200 OK; Roar Savanna
    Great! I’ve indexed it.
    

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34. 1xx —
    2xx —
    3xx —
    4xx —
    5xx —
    STATUS CODES
    Informational
    Success!!
    Redirection
    Client Error
    Server Error
    PRO-TIP!
    Learn a lot more about
    status codes by going to
    httpstatuses.com
    

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35. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    def eat_hippo
    consume_hippo if @current_user.lion?
    head :no_content # 204
    end
    end
    app/controllers/safari_controller.rb
    

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36. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    def eat_hippo
    consume_hippo if @current_user.lion?
    head :no_content # 204
    end
    end
    app/controllers/safari_controller.rb
    

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37. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    def eat_hippo
    consume_hippo if @current_user.lion?
    head :no_content # 204
    end
    end
    app/controllers/safari_controller.rb
    

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38. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    def eat_hippo
    consume_hippo if @current_user.lion?
    head :no_content # 204
    end
    end
    app/controllers/safari_controller.rb
    

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39. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    def eat_hippo
    consume_hippo if @current_user.lion?
    head :no_content # 204
    end
    end
    app/controllers/safari_controller.rb
    

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40. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    before_action { @hippo = Hippo.first }
    before_action { redirect_to oasis_url if dry_season? }
    def find_hippo
    render :hippo
    end
    end
    app/controllers/safari_controller.rb
    

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41. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    before_action { @hippo = Hippo.first }
    before_action { redirect_to oasis_url if dry_season? }
    def find_hippo
    render :hippo
    end
    end
    app/controllers/safari_controller.rb
    app/controllers/hello_controller.rb
    < HTTP/1.1 302 Found
    < Location: https://www.skylight.io/oasis
    < Content-Type: text/plain
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    

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42. View Slide

43. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    before_action { @hippo = Hippo.first }
    def find_hippo
    redirect_to oasis_url, status: :moved_permanently
    end
    end
    app/controllers/safari_controller.rb
    app/controllers/hello_controller.rb
    < HTTP/1.1 301 Moved Permanently
    < Location: https://www.skylight.io/oasis
    < Content-Type: text/plain
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    

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44. app/controllers/hello_controller.rb
    Rails.application.routes.draw do
    get '/find-hippo', to: redirect('/oasis')
    end
    config/routes.rb
    app/controllers/hello_controller.rb
    < HTTP/1.1 301 Moved Permanently
    < Location: https://www.skylight.io/oasis
    < Content-Type: text/plain
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    

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45. DANGER!
    

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46. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    before_action { @hippo = Hippo.first }
    def find_hippo
    redirect_to oasis_url if dry_season?
    render :hippo
    end
    end
    app/controllers/safari_controller.rb
    

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47. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    before_action { @hippo = Hippo.first }
    def find_hippo
    redirect_to oasis_url if dry_season?
    render :hippo
    end
    end
    app/controllers/safari_controller.rb
    http://skylight.io/find-hippo
    

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48. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    before_action { @hippo = Hippo.first }
    before_action { redirect_to oasis_url if dry_season? }
    def find_hippo
    render :hippo
    end
    end
    app/controllers/safari_controller.rb
    

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49. Here’s a GET request for /safari, Host header is skylight.io
    200 OK; Roar Savanna
    Great, I can render that.
    Wait…I need more information.
    

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50. Here’s a GET request for /safari, Host header is skylight.io
    200 OK; Roar Savanna
    Great, I can render that.
    Wait…I need more information.
    Oh yeah. It’s a plain text response.
    Oh! OK!
    

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51. app/controllers/hello_controller.rb
    env = {
    'REQUEST_METHOD' => 'GET',
    'PATH_INFO' => ‘/safari',
    'HTTP_HOST' => 'skylight.io',
    # ...
    }
    status, headers, body = app.call(env)
    status # => 200
    headers # => { 'Content-Type' => 'text/plain' }
    body # => [‘Roar Savanna’]
    server.rb
    1
    2 The Response Array
    

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52. app/controllers/hello_controller.rb
    < HTTP/1.1 302 Found
    < Content-Type: text/plain
    < Location: https://www.skylight.io/oasis
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    

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53. app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Content-Type: text/plain
    < Content-Length: 12
    < Set-Cookie: _safari_session=some-token;
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < Roar Savanna
    

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54. app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Content-Type: text/plain
    < Content-Length: 12
    < Set-Cookie: _safari_session=some-token;
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < Roar Savanna
    

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55. app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Content-Type: text/plain
    < Content-Length: 12
    < Set-Cookie: _safari_session=some-token;
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < Roar Savanna
    

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56. app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Content-Type: text/plain
    < Content-Length: 12
    < Set-Cookie: _safari_session=some-token;
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < Roar Savanna
    

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57. app/controllers/hello_controller.rb
    response.headers['HEADER NAME'] = 'header value'
    

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58. Here’s a GET request for /safari, Host header is skylight.io
    …
    200 OK; Roar Savanna
    Thanks!
    

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59. Here’s a GET request for /safari, Host header is skylight.io
    200 OK; Roar Savanna
    Here’s a GET request for /safari, Host header is skylight.io
    Just use the last 200
    Nice!
    Thanks!
    

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60. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    before_action { @hippo = Hippo.first }
    def find_hippo
    render :hippo
    end
    end
    app/controllers/safari_controller.rb
    PRO-TIP!
    Turn on caching in
    development by running
    rails dev:cache
    

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61. HIPPOS ARE BIG
    

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62. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    before_action { @hippo = Hippo.first }
    def find_hippo
    http_cache_forever { render :hippo }
    end
    end
    app/controllers/safari_controller.rb
    app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Content-Type: text/html
    < Cache-Control: max-age=3155695200, private
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < …
    

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63. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    before_action { @hippo = Hippo.first }
    def find_hippo
    http_cache_forever { render :hippo }
    end
    end
    app/controllers/safari_controller.rb
    app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Content-Type: text/html
    < Cache-Control: max-age=3155695200, private
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < …
    

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64. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    before_action { @hippo = Hippo.first }
    def find_hippo
    http_cache_forever(public: true) { render :hippo }
    end
    end
    app/controllers/safari_controller.rb
    app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Content-Type: text/html
    < Cache-Control: max-age=3155695200, public
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < …
    

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65. app/controllers/hello_controller.rb
    <%= image_tag "hippo.png" %>
    app/views/safari/hippo.html.erb
    

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66. app/controllers/hello_controller.rb
    <%= image_tag "hippo.png" %>
    app/views/safari/hippo.html.erb
    app/controllers/hello_controller.rb
    http://skylight.io/find-hippo
    ca1895ae8ed0a09237f6992015fef1e11be77c023.png">
    

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67. app/controllers/hello_controller.rb
    <%= image_tag "hippo.png" %>
    app/views/safari/hippo.html.erb
    app/controllers/hello_controller.rb
    http://skylight.io/find-hippo
    ca1895ae8ed0a09237f6992015fef1e11be77c023.png">
    

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68. app/controllers/hello_controller.rb
    <%= image_tag "hippo.png" %>
    app/views/safari/hippo.html.erb
    app/controllers/hello_controller.rb
    http://skylight.io/find-hippo
    ca1895ae8ed0a09237f6992015fef1e11be77c023.png">
    

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69. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    before_action { @hippo = Hippo.first }
    def find_hippo
    http_cache_forever { render :hippo }
    end
    end
    app/controllers/safari_controller.rb
    app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Content-Type: text/html
    < Cache-Control: max-age=3155695200, private
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < …
    

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70. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    before_action { @hippo = Hippo.first }
    def find_hippo
    expires_in 1.hour
    render :hippo
    end
    end
    app/controllers/safari_controller.rb
    app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Content-Type: text/html
    < Cache-Control: max-age=3600, private
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < …
    

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71. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    before_action { @hippo = Hippo.first }
    def find_hippo
    expires_in 1.hour
    render :hippo
    end
    end
    app/controllers/safari_controller.rb
    app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Content-Type: text/html
    < Cache-Control: max-age=3600, private
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < …
    

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72. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    before_action { @hippo = Hippo.first }
    def find_hippo
    render :hippo
    end
    end
    app/controllers/safari_controller.rb
    

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73. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    before_action { @hippo = Hippo.first }
    def find_hippo
    render :hippo
    end
    end
    app/controllers/safari_controller.rb
    app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Content-Type: text/html
    < Cache-Control: max-age=0, private, must-revalidate
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < …
    

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74. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    before_action { @hippo = Hippo.first }
    def find_hippo
    render :hippo
    end
    end
    app/controllers/safari_controller.rb
    app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Content-Type: text/html
    < Cache-Control: max-age=0, private, must-revalidate
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < …
    

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75. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    before_action { @hippo = Hippo.first }
    def find_hippo
    render :hippo
    end
    end
    app/controllers/safari_controller.rb
    app/controllers/hello_controller.rb
    
    
    
    Safari
    href="/assets/application-gobbledygook.css" />
    
    
    
    

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76. app/controllers/hello_controller.rb
    # a simplified Rack::ETag
    module Rack
    class ETag
    def initialize(app)
    @app = app
    end
    def call(env)
    status, headers, body = @app.call(env)
    if status == 200
    digest = digest_body(body)
    headers[Etag] = %(W/"#{digest}")
    end
    [status, headers, body]
    end
    private
    #...
    end
    end
    rack/lib/rack/etag.rb
    

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77. app/controllers/hello_controller.rb
    # a simplified Rack::ETag
    module Rack
    class ETag
    def initialize(app)
    @app = app
    end
    def call(env)
    status, headers, body = @app.call(env)
    if status == 200
    digest = digest_body(body)
    headers[Etag] = %(W/"#{digest}")
    end
    [status, headers, body]
    end
    private
    #...
    end
    end
    rack/lib/rack/etag.rb
    app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Content-Type: text/html
    < Cache-Control: max-age=0, private, must-revalidate
    < ETag: W/“48a7e47309e0ec54e32df3a272094025"
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < …
    

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78. app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Content-Type: text/html
    < Cache-Control: max-age=0, private, must-revalidate
    < ETag: W/“48a7e47309e0ec54e32df3a272094025"
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < …
    app/controllers/hello_controller.rb
    > GET /find-hippo HTTP/1.1
    > Host: skylight.io
    > If-None-Match: W/"48a7e47309e0ec54e32df3a272094025"
    

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79. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    before_action { @hippo = Hippo.first }
    def find_hippo
    render :hippo
    end
    end
    app/controllers/safari_controller.rb
    app/controllers/hello_controller.rb
    
    
    
    Safari
    href="/assets/application-gobbledygook.css" />
    
    
    
    

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80. app/controllers/hello_controller.rb
    # a simplified Rack::ETag
    module Rack
    class ETag
    def initialize(app)
    @app = app
    end
    def call(env)
    status, headers, body = @app.call(env)
    if status == 200
    digest = digest_body(body)
    headers[Etag] = %(W/"#{digest}")
    end
    [status, headers, body]
    end
    private
    #...
    end
    end
    rack/lib/rack/etag.rb
    

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81. app/controllers/hello_controller.rb
    # a simplified Rack::ETag
    module Rack
    class ETag
    def initialize(app)
    @app = app
    end
    def call(env)
    status, headers, body = @app.call(env)
    if status == 200
    digest = digest_body(body)
    headers[Etag] = %(W/"#{digest}")
    end
    [status, headers, body]
    end
    private
    #...
    end
    end
    rack/lib/rack/etag.rb
    

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82. app/controllers/hello_controller.rb
    # a simplified Rack::ETag
    module Rack
    class ETag
    def initialize(app)
    @app = app
    end
    def call(env)
    status, headers, body = @app.call(env)
    if status == 200
    digest = digest_body(body)
    headers[Etag] = %(W/"#{digest}")
    end
    [status, headers, body]
    end
    private
    #...
    end
    end
    rack/lib/rack/etag.rb
    app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Content-Type: text/html
    < Cache-Control: max-age=0, private, must-revalidate
    < ETag: W/“48a7e47309e0ec54e32df3a272094025"
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < …
    

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83. app/controllers/hello_controller.rb
    # a simplified Rack::ConditionalGet
    module Rack
    class ConditionalGet
    def initialize(app)
    @app = app
    end
    def call(env)
    status, headers, body = @app.call(env)
    if status == 200 && etag_matches?
    status = 304
    body = []
    end
    [status, headers, body]
    end
    private
    def etag_matches?
    headers['ETag'] == env['HTTP_IF_NONE_MATCH']
    end
    end
    end
    rack/lib/rack/conditional_get.rb
    

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84. app/controllers/hello_controller.rb
    # a simplified Rack::ConditionalGet
    module Rack
    class ConditionalGet
    def initialize(app)
    @app = app
    end
    def call(env)
    status, headers, body = @app.call(env)
    if status == 200 && etag_matches?
    status = 304
    body = []
    end
    [status, headers, body]
    end
    private
    def etag_matches?
    headers['ETag'] == env['HTTP_IF_NONE_MATCH']
    end
    end
    end
    rack/lib/rack/conditional_get.rb
    app/controllers/hello_controller.rb
    < HTTP/1.1 304 Not Modified
    < Cache-Control: max-age=0, private, must-revalidate
    < ETag: W/“48a7e47309e0ec54e32df3a272094025”
    < Content-Type: text/html
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    

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85. app/controllers/hello_controller.rb
    # a simplified Rack::ConditionalGet
    module Rack
    class ConditionalGet
    def initialize(app)
    @app = app
    end
    def call(env)
    status, headers, body = @app.call(env)
    if status == 200 && etag_matches?
    status = 304
    body = []
    end
    [status, headers, body]
    end
    private
    def etag_matches?
    headers['ETag'] == env['HTTP_IF_NONE_MATCH']
    end
    end
    end
    rack/lib/rack/conditional_get.rb
    app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Cache-Control: max-age=0, private, must-revalidate
    < ETag: W/“48a7e47309e0ec54e32df3a272094025”
    < Content-Type: text/html
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < …
    

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86. View Slide

87. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    before_action { @hippo = Hippo.first }
    def find_hippo
    render :hippo if stale?(@hippo)
    end
    end
    app/controllers/safari_controller.rb
    app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Content-Type: text/html
    < Cache-Control: max-age=0, private, must-revalidate
    < ETag: W/“48a7e47309e0ec54e32df3a272094025"
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < …
    app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Content-Type: text/html
    < Cache-Control: max-age=0, private, must-revalidate
    < ETag: W/"60bee75b8031cda7761a332685151766"
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < …
    

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88. app/controllers/hello_controller.rb
    
    
    
    Safari
    href="/assets/application-gobbledygook.css" />
    
    
    
    
    
    

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89. app/controllers/hello_controller.rb
    "hippo/1-20071224150000"
    

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90. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    before_action { @hippo = Hippo.first }
    def find_hippo
    render :hippo if stale?(@hippo)
    end
    end
    app/controllers/safari_controller.rb
    app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Content-Type: text/html
    < Cache-Control: max-age=0, private, must-revalidate
    < ETag: W/"60bee75b8031cda7761a332685151766"
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < …
    

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91. View Slide

92. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    before_action { @hippo = Hippo.first }
    def find_hippo
    response.headers["Cache-Control"] = "no-store"
    render :hippo
    end
    end
    app/controllers/safari_controller.rb
    app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Content-Type: text/html
    < Cache-Control: no-store
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < …
    

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93. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    before_action { @hippo = Hippo.first }
    def find_hippo
    response.headers["Cache-Control"] = "no-store"
    render :hippo
    end
    end
    app/controllers/safari_controller.rb
    app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Content-Type: text/html
    < Cache-Control: no-store
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < …
    no-store ≠ no-cache
    

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94. THE RESPONSE BODY
    and finally…
    

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95. app/controllers/hello_controller.rb
    env = {
    'REQUEST_METHOD' => 'GET',
    'PATH_INFO' => ‘/safari',
    'HTTP_HOST' => 'skylight.io',
    # ...
    }
    status, headers, body = app.call(env)
    status # => 200
    headers # => { 'Content-Type' => 'text/plain' }
    body # => [‘Roar Savanna’]
    server.rb
    1
    2
    3
    The Response Array
    

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96. app/controllers/hello_controller.rb
    class SafariController < ApplicationController
    before_action { @hippo = Hippo.first }
    def find_hippo
    render :hippo
    end
    end
    app/controllers/safari_controller.rb
    app/controllers/hello_controller.rb
    
    
    
    Safari
    href="/assets/application-gobbledygook.css" />
    
    
    
    

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97. app/controllers/hello_controller.rb
    < HTTP/1.1 200 OK
    < Content-Type: text/html
    < Date: Thu, 25 Apr 2019 18:52:54 GMT
    <
    < …
    

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98. http://skylight.io/safari.html
    

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99. app/controllers/hello_controller.rb
    > GET /find-hippo HTTP/1.1
    > Host: skylight.io
    > Accept: text/html,application/xhtml+xml,application/xml;
    

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100. app/controllers/hello_controller.rb
     class SafariController < ApplicationController
     before_action { @hippo = Hippo.first }
     def find_hippo
     render :hippo
     end
     end
     app/controllers/safari_controller.rb
     

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101. http://skylight.io/find-hippo.json
     

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102. http://skylight.io/find-hippo.json
     

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103. app/controllers/hello_controller.rb
     class SafariController < ApplicationController
     before_action { @hippo = Hippo.first }
     def find_hippo
     respond_to do |format|
     format.html { render :hippo }
     format.json { render json: @hippo }
     end
     end
     end
     app/controllers/safari_controller.rb
     

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104. http://skylight.io/find-hippo
     {
     "id": 1,
     "name": "Jason",
     "created_at": "2020-04-10T17:14:20.771Z",
     "updated_at": "2020-04-10T17:14:20.771Z"
     }
     app/controllers/hello_controller.rb
     < HTTP/1.1 200 OK
     < Cache-Control: max-age=0, private, must-revalidate
     < Date: Thu, 25 Apr 2019 18:52:54 GMT
     < Content-Type: application/json
     <
     < {"id": 1, "name": “Jason", … }
     

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105. app/controllers/hello_controller.rb
     < HTTP/1.1 200 OK
     < Content-Type: text/html
     < X-Content-Type-Options: nosniff
     < Cache-Control: max-age=0, private, must-revalidate
     < Date: Thu, 25 Apr 2019 18:52:54 GMT
     <
     < …
     

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106. TEMPLATE RENDERING
     

     View Slide

107. app/controllers/hello_controller.rb
     class SafariController < ApplicationController
     before_action { @hippo = Hippo.first }
     def find_hippo
     render :hippo
     end
     end
     app/controllers/safari_controller.rb
     

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108. app/controllers/hello_controller.rb
     class SafariController < ApplicationController
     before_action { @hippo = Hippo.first }
     def find_hippo
     render :hippo
     end
     end
     app/controllers/safari_controller.rb
     app/controllers/hello_controller.rb
     Hey <%= current_user.name %>, meet <%= link_to @hippo.name, @hippo %>!
     app/views/safari/hippo.html.erb
     

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109. app/controllers/hello_controller.rb
     class SafariControllerViewContext < ActionView::Base
     include Rails::AllTheHelpers
     # link_to, etc.
     include MyApp::AllTheHelpers
     # current_user, etc.
     def initialize(assigns)
     assigns.each { |k, v| instance_variable_set("@#{k}", v) }
     end
     private
     # Hey <%= current_user.name %>, meet
     # <%= link_to @hippo.name, @hippo %>!
     def __compiled_app_templates_hippo_erb
     output = ""
     output << "Hey "
     output << html_escape(current_user.name)
     output << ", meet"
     output << link_to(html_escape(@hippo.name), @hippo)
     output << "!"
     output
     end
     end
     NOTE: To see the actual code, look in ActionView!::Rendering, ActionView!::Base,
     ActionView!::Renderer, ActionView!::TemplateRenderer, ActionView!::Template
     

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110. app/controllers/hello_controller.rb
     class SafariControllerViewContext < ActionView::Base
     include Rails::AllTheHelpers
     # link_to, etc.
     include MyApp::AllTheHelpers
     # current_user, etc.
     def initialize(assigns)
     assigns.each { |k, v| instance_variable_set("@#{k}", v) }
     end
     private
     # Hey <%= current_user.name %>, meet
     # <%= link_to @hippo.name, @hippo %>!
     def __compiled_app_templates_hippo_erb
     output = ""
     output << "Hey "
     output << html_escape(current_user.name)
     output << ", meet"
     output << link_to(html_escape(@hippo.name), @hippo)
     output << "!"
     output
     end
     end
     

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111. app/controllers/hello_controller.rb
     class SafariControllerViewContext < ActionView::Base
     include Rails::AllTheHelpers
     # link_to, etc.
     include MyApp::AllTheHelpers
     # current_user, etc.
     def initialize(assigns)
     assigns.each { |k, v| instance_variable_set("@#{k}", v) }
     end
     private
     # Hey <%= current_user.name %>, meet
     # <%= link_to @hippo.name, @hippo %>!
     def __compiled_app_templates_hippo_erb
     output = ""
     output << "Hey "
     output << html_escape(current_user.name)
     output << ", meet"
     output << link_to(html_escape(@hippo.name), @hippo)
     output << "!"
     output
     end
     end
     

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112. app/controllers/hello_controller.rb
     class SafariControllerViewContext < ActionView::Base
     include Rails::AllTheHelpers
     # link_to, etc.
     include MyApp::AllTheHelpers
     # current_user, etc.
     def initialize(assigns)
     assigns.each { |k, v| instance_variable_set("@#{k}", v) }
     end
     private
     # Hey <%= current_user.name %>, meet
     # <%= link_to @hippo.name, @hippo %>!
     def __compiled_app_templates_hippo_erb
     output = ""
     output << "Hey "
     output << html_escape(current_user.name)
     output << ", meet"
     output << link_to(html_escape(@hippo.name), @hippo)
     output << "!"
     output
     end
     end
     

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113. app/controllers/hello_controller.rb
     class SafariControllerViewContext < ActionView::Base
     include Rails::AllTheHelpers
     # link_to, etc.
     include MyApp::AllTheHelpers
     # current_user, etc.
     def initialize(assigns)
     assigns.each { |k, v| instance_variable_set("@#{k}", v) }
     end
     private
     # Hey <%= current_user.name %>, meet
     # <%= link_to @hippo.name, @hippo %>!
     def __compiled_app_templates_hippo_erb
     output = ""
     output << "Hey "
     output << html_escape(current_user.name)
     output << ", meet"
     output << link_to(html_escape(@hippo.name), @hippo)
     output << "!"
     output
     end
     end
     

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114. app/controllers/hello_controller.rb
     class SafariControllerViewContext < ActionView::Base
     include Rails::AllTheHelpers
     # link_to, etc.
     include MyApp::AllTheHelpers
     # current_user, etc.
     def initialize(assigns)
     assigns.each { |k, v| instance_variable_set("@#{k}", v) }
     end
     private
     # Hey <%= current_user.name %>, meet
     # <%= link_to @hippo.name, @hippo %>!
     def __compiled_app_templates_hippo_erb
     output = ""
     output << "Hey "
     output << html_escape(current_user.name)
     output << ", meet"
     output << link_to(html_escape(@hippo.name), @hippo)
     output << "!"
     output
     end
     end
     

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115. app/controllers/hello_controller.rb
     class SafariControllerViewContext < ActionView::Base
     include Rails::AllTheHelpers
     # link_to, etc.
     include MyApp::AllTheHelpers
     # current_user, etc.
     def initialize(assigns)
     assigns.each { |k, v| instance_variable_set("@#{k}", v) }
     end
     private
     # Hey <%= current_user.name %>, meet
     # <%= link_to @hippo.name, @hippo %>!
     def __compiled_app_templates_hippo_erb
     output = ""
     output << "Hey "
     output << html_escape(current_user.name)
     output << ", meet"
     output << link_to(html_escape(@hippo.name), @hippo)
     output << "!"
     output
     end
     end
     

     View Slide

116. app/controllers/hello_controller.rb
     class SafariControllerViewContext < ActionView::Base
     include Rails::AllTheHelpers
     # link_to, etc.
     include MyApp::AllTheHelpers
     # current_user, etc.
     def initialize(assigns)
     assigns.each { |k, v| instance_variable_set("@#{k}", v) }
     end
     private
     # Hey <%= current_user.name %>, meet
     # <%= link_to @hippo.name, @hippo %>!
     def __compiled_app_templates_hippo_erb
     output = ""
     output << "Hey "
     output << html_escape(current_user.name)
     output << ", meet"
     output << link_to(html_escape(@hippo.name), @hippo)
     output << "!"
     output
     end
     end
     

     View Slide

117. app/controllers/hello_controller.rb
     class SafariControllerViewContext < ActionView::Base
     include Rails::AllTheHelpers
     # link_to, etc.
     include MyApp::AllTheHelpers
     # current_user, etc.
     def initialize(assigns)
     assigns.each { |k, v| instance_variable_set("@#{k}", v) }
     end
     private
     # Hey <%= current_user.name %>, meet
     # <%= link_to @hippo.name, @hippo %>!
     def __compiled_app_templates_hippo_erb
     output = ""
     output << "Hey "
     output << html_escape(current_user.name)
     output << ", meet"
     output << link_to(html_escape(@hippo.name), @hippo)
     output << "!"
     output
     end
     end
     

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118. app/controllers/hello_controller.rb
     class SafariControllerViewContext < ActionView::Base
     include Rails::AllTheHelpers
     # link_to, etc.
     include MyApp::AllTheHelpers
     # current_user, etc.
     def initialize(assigns)
     assigns.each { |k, v| instance_variable_set("@#{k}", v) }
     end
     private
     # Hey <%= current_user.name %>, meet
     # <%= link_to @hippo.name, @hippo %>!
     def __compiled_app_templates_hippo_erb
     output = ""
     output << "Hey "
     output << html_escape(current_user.name)
     output << ", meet"
     output << link_to(html_escape(@hippo.name), @hippo)
     output << "!"
     output
     end
     end
     

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119. http://skylight.io/find-hippo
     
     
     
     Safari
     
     
     
     
     Hey RailsConf, meet Phyllis!
     
     
     Hey RailsConf, meet Phyllis!
     

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120. http://skylight.io/find-hippo
     
     
     
     Safari
     
     
     
     
     Hey RailsConf, meet Phyllis!
     
     
     Hey RailsConf, meet Phyllis! app/controllers/hello_controller.rb
     < HTTP/1.1 200 OK
     < Content-Type: text/html
     < Content-Length: 306
     < Cache-Control: max-age=0, private, must-revalidate
     < ETag: W/“60bee75b8031cda7761a332685151766”
     < Set-Cookie: _safari_session=some-session-token; path=/;
     < X-Content-Type-Options: nosniff
     < Date: Thu, 25 Apr 2019 18:52:54 GMT
     

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121. View Slide