LinuxTag 2013 - "Cache = Cash"

Transcript

1. Cache = Cash
   stefan.wintermeyer@amooma.de @wintermeyer
   Stefan Wintermeyer
   

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2. 1 2 3
   Why? How? Autobahn!
   

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3. Today we only
   discuss dynamic
   HTML which gets
   rendered views!
   This talk is about
   Rails stuff. But you
   can use the same
   ideas with PHP, etc.
   

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4. 1 Why?
   

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5. a) Save money!
   

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6. If you can deliver a
   webpage in half the
   time you only need half
   the amount of servers.
   

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7. b) Snappiness
   

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8. What's the impact of slow sites?
   Lower conversions and engagement, higher bounce rates...
   Ilya Grigorik @igrigorik
   Make The Web Faster, Google
   Have a look at
   Ilya‘s book!
   

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9. Performance Related Changes and their User Impact
   Web Search Delay Experiment
   @igrigorik
   • The cost of delay increases over time and persists
   • Delays under half a second impact business metrics
   • "Speed matters" is not just lip service
   Type of Delay Delay (ms) Duration
   (weeks)
   Impact on Avg.
   Daily Searches
   Pre-header 50 4 Not
   measurable
   Pre-header 100 4 -0.20%
   Post-header 200 6 -0.59%
   Post-header 400 6 -0.59%
   Post-ads 200 4 -0.30%
   

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10. Performance Related Changes and their User Impact
    Server Delays Experiment
    • Strong negative impacts
    • Roughly linear changes with increasing delay
    • Time to Click changed by roughly double the delay
    @igrigorik
    

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11. Yo ho ho and a few billion pages of RUM
    How speed affects bounce rate
    @igrigorik
    

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12. Usability Engineering 101
    Delay User reaction
    0 - 100 ms Instant
    100 - 300 ms Feels sluggish
    300 - 1000 ms Machine is working...
    1 s+ Mental context switch
    10 s+ I'll come back later...
    Stay under 250
    ms to feel "fast".
    Stay under 1000
    ms to keep users
    attention.
    @igrigorik
    

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13. For many, mobile is the one and only internet
    device!
    Country Mobile-only users
    Egypt 70%
    India 59%
    South Africa 57%
    Indonesia 44%
    United States 25%
    onDevice Research
    @igrigorik
    

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14. The (short) life of our 1000 ms budget
    3G (200 ms
    RTT)
    4G(80 ms RTT)
    Control plane (200-2500 ms) (50-100 ms)
    DNS lookup 200 ms 80 ms
    TCP Connection 200 ms 80 ms
    TLS handshake (200-400 ms) (80-160 ms)
    HTTP request 200 ms 80 ms
    Leftover budget 0-400 ms 500-760 ms
    Network overhead
    of one HTTP
    request!
    @igrigorik
    The broswer
    needs 100 -
    150ms to
    render the
    page.
    

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15. 2 How?
    

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16. Raspberry Pi
    

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17. Software Stack
    • Ruby on Rails 3.2 (no need to wait till 4.0)
    • Ruby 1.9.3
    • Nginx
    • Unicorn
    • MySQL
    • Raspbian Wheezy
    

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18. Example:
    Online Shop
    

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19. The Models
    

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20. Cart
    state string
    LineItem
    price decimal (8,2)
    quantity integer
    Category
    name string
    Product
    description text
    name string
    price decimal (8,2)
    DiscountGroup
    discount integer
    name string
    User
    email string ∗
    encrypted_password string ∗
    first_name string
    last_name string
    Rating
    value integer
    

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21. The UI
    

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23. current_user
    

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27. Bob‘s cart
    

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29. Discounted price
    

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30. Rate this product
    

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31. Measure the
    Success
    

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32. Watir script
    http://watir.com
    

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33. require 'watir-webdriver'
    url = 'http://ip.address:3000'
    b = Watir::Browser.new
    # An anonymous user looks around.
    #
    ['AA', 'AB', 'AH'].each do |product_name|
    b.goto url
    Watir::Wait.until { b.link(:text,
    product_name).exist? }
    b.link(:text, product_name).click
    Watir::Wait.until { b.link(:text,
    'Webshop').exist? }
    b.link(:text, 'Webshop').click
    end
    3 different products
    

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35. bob@aol.com
    

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36. Login Bob
    b.goto url
    b.goto "#{url}/users/sign_in"
    b.text_field(:id,
    "user_email").set("bob@aol.com")
    b.text_field(:id, "user_password").set("123")
    b.button(:name, "commit").click
    

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37. Bob looks around too
    ['AA', 'AB', 'AH'].each do |product_name|
    b.goto url
    Watir::Wait.until { b.link(:text,
    product_name).exist? }
    b.link(:text, product_name).click
    Watir::Wait.until { b.link(:text,
    'Webshop').exist? }
    b.link(:text, 'Webshop').click
    end
    

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38. Bob rates products
    ['AA', 'AD', 'AI'].each do |product_name|
    b.goto url
    b.link(:text, product_name).click
    star_id = 'product_' + product_name +
    '_rating_2'
    b.link(:id, star_id).click
    end
    

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39. Bob fills his cart
    [1, 3, 5].each do |product_id|
    b.goto url
    add_button_id = 'add_' + product_id.to_s
    b.link(:id, add_button_id).click
    end
    

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40. Logout
    b.link(:text, 'Logout').click
    

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41. Total: 43 webpages
    

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42. 30 sec. localhost demo
    run through the script
    

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44. How fast or slow is on
    the Raspberry Pi?
    

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45. 0
    29
    58
    87
    116
    Vanilla
    116 s
    

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46. /
    Started GET "/" for x.x.x.x at 2013-02-28 21:05:34 +0000
    Processing by ProductsController#index as HTML
    Rendered products/index.html.haml within layouts/application
    (3022.3ms)
    Rendered layouts/_navbar.html.haml (12.5ms)
    Rendered layouts/_footer.html.haml (2.9ms)
    Completed 200 OK in 3097ms (Views: 3013.3ms | ActiveRecord:
    72.6ms)
    

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47. Started GET "/" for x.x.x.x at 2013-02-28 21:05:34 +0000
    Processing by ProductsController#index as HTML
    Rendered products/index.html.haml within layouts/application
    (3022.3ms)
    Rendered layouts/_navbar.html.haml (12.5ms)
    Rendered layouts/_footer.html.haml (2.9ms)
    Completed 200 OK in 3097ms (Views: 3013.3ms | ActiveRecord:
    72.6ms)
    3013.3ms
    

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48. Fragment
    Caching
    aka Easy Money
    

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49. Vanilla HAML Version
    %table.table.table-striped{:id => 'products'}
    %thead
    %tr
    %th Name
    %th Category
    [...]
    %tbody
    - @products.each do |product|
    %tr
    %td= link_to product.name,
    [...]
    %td= product.description
    

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50. Russian Doll
    - cache [current_user, @products] do
    %table.table.table-striped{:id =>
    'products'}
    %thead
    %tr
    %th Name
    %th Category
    [...]
    %tbody
    - @products.each do |product|
    - cache [current_user, product] do
    %tr
    %td= link_to product.name,
    [...]
    %td= product.description
    complete table
    single row
    

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51. complete table
    single row
    

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52. Add these line to your Gemfile:
    gem 'dalli'
    gem 'cache_digests'
    Don‘t forget to run bundle install.
    

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53. production.rb:
    config.cache_store = :dalli_store
    

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54. Seriously, how
    much difference
    can 5 LOC
    make?!
    

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55. 0
    30
    60
    90
    120
    Vanilla Fragment Caching (4 LOC)
    116 s 60 s
    

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56. 5 LOC result in
    50% fewer
    servers!
    

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57. It‘s all about
    the details.
    

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58. •Each row and each table (#index).
    •Each #show content.
    •The shopping cart.
    •The navigation bar and the footer.
    

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59. Don‘t just use a plain
    russian doll cache.
    Cluster the little dolls!
    

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60. Cluster of 10
    Cluster of 10
    

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61. Just 2 hours of
    optimizing save
    another 15 ms.
    

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62. 0
    30
    60
    90
    120
    Vanilla Fragment Caching
    116 s 45 s
    

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63. Remember DHH‘s
    Keynote which showed
    how to use JavaScript
    to further optimize
    fragment caching.
    

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64. Important:
    You need a clean
    database structure!
    

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65. HTTP Caching
    

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66. Web browsers and proxies
    don‘t want to fetch webpages
    twice.
    They use Last-Modified and Etag
    to avoid that.
    

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67. The idea of Last-Modified
    

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68. Web browser:
    „Hello web server. How‘s life?
    My user wants to have a look at
    xyz.html. I cached a copy last
    week.
    Is that still good?“
    

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69. Web server:
    „Hi! Good to see you again!
    xyz.html hasn‘t changed since
    last week.
    Have a nice day!“
    aka 304 Not Modified
    

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70. The curl version for Etag
    

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71. > curl -I http://0.0.0.0:3000/
    HTTP/1.1 200 OK
    Content-Type: text/html; charset=utf-8
    X-Ua-Compatible: IE=Edge
    Etag: "9a779b80e4b0ac3c60d29807e302deb7"
    [...]
    > curl -I http://0.0.0.0:3000/
    HTTP/1.1 200 OK
    Content-Type: text/html; charset=utf-8
    X-Ua-Compatible: IE=Edge
    Etag: "fa8fc1e981833a6885b583d351c4d823"
    

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72. > curl -I http://0.0.0.0:3000/
    HTTP/1.1 200 OK
    Content-Type: text/html; charset=utf-8
    X-Ua-Compatible: IE=Edge
    Etag: "9a779b80e4b0ac3c60d29807e302deb7"
    [...]
    > curl -I http://0.0.0.0:3000/
    HTTP/1.1 200 OK
    Content-Type: text/html; charset=utf-8
    X-Ua-Compatible: IE=Edge
    Etag: "fa8fc1e981833a6885b583d351c4d823"
    

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73. Set the Etag
    class ProductsController <
    ApplicationController
    # GET /products
    def index
    @products = Product.limit(25)
    fresh_when :etag => [current_user,
    @products.order(:updated_at).last]
    end
    [...]
    

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74. Set the Etag
    class ProductsController <
    ApplicationController
    # GET /products
    def index
    @products = Product.limit(25)
    fresh_when :etag => [current_user,
    @products.order(:updated_at).last]
    end
    [...]
    

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75. > curl -I http://0.0.0.0:3000/ -c
    cookies.txt
    HTTP/1.1 200 OK
    Etag: "4d348810e69400799e2ab684c0ef4777"
    > curl -I http://0.0.0.0:3000/ -b
    cookies.txt
    HTTP/1.1 200 OK
    Etag: "4d348810e69400799e2ab684c0ef4777"
    The cookie is needed for the CSRF-Token.
    

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76. > curl -I http://0.0.0.0:3000/ -b
    cookies.txt --header 'If-None-Match:
    "4d348810e69400799e2ab684c0ef4777"'
    HTTP/1.1 304 Not Modified
    Etag: "4d348810e69400799e2ab684c0ef4777"
    304!
    

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77. The beauty of HTTP
    caching is that the
    view isn‘t rendered.
    

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78. 0
    30
    60
    90
    120
    Vanilla Fragment Caching HTTP Cache
    45 s 35 s
    

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79. Not good enough?
    

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80. We waste a lot of
    time writing the
    initial cache!
    

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81. We could preheat
    the cache in off
    business hours!
    

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82. 0
    30
    60
    90
    120
    Vanilla Fragment Caching HTTP Cache Preheater
    26 s
    

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83. Use the night to
    preheat your cache.
    And don‘t be afraid
    of brute force!
    

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84. 3 Autobahn!
    

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85. The fastest page is
    delivered by Nginx
    without ever asking
    Rails.
    

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86. ᵓᴷᴷ Gemfile
    ᵓᴷᴷ [...]
    ᵓᴷᴷ public
    ᴹ ᵓᴷᴷ 404.html
    ᴹ ᵓᴷᴷ 422.html
    ᴹ ᵓᴷᴷ 500.html
    ᴹ ᵓᴷᴷ favicon.ico
    ᴹ ᵋᴷᴷ robots.txt
    ᵓᴷᴷ [...]
    That‘s already
    done for the
    files in the
    public directory.
    

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87. Is there an easy way to
    save complete pages
    which are rendered by
    the Rails framework?
    

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88. Add caches_page to your
    controller to save views as static
    gz files in your public directory:
    caches_page :index, :show,
    :gzip => :true
    

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89. Again: Brute Force is your
    friend. The server has a
    hard time to keep awake at
    night any way.
    

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90. Tricky part:
    How to delete out of date
    gz files?
    

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91. after_update :expire_cache
    before_destroy :expire_cache
    private
    def expire_cache
    ActionController::Base.expire_page(Rails.application.routes.url_h
    elpers.company_path(self))
    ActionController::Base.expire_page(Rails.application.routes.url_h
    elpers.companies_path)
    end
    app/models/product.rb
    

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92. 0
    30
    60
    90
    120
    Vanilla Fragment Caching HTTP Cache Preheater Page Caching
    19 s
    6.1 x faster!
    

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93. caches_page
    vs.
    !current_user.nil?
    ???
    

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94. caches_page is good to cache
    customized user content too.
    It just takes more thinking.
    

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95. Let us assume a user base
    of 10,000,000 people.
    

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96. /tmp ᐅ wget http://www.railsconf.com/2013/talks
    --2013-04-27 21:04:24-- http://www.railsconf.com/2013/talks
    Resolving www.railsconf.com... 107.20.162.205
    Connecting to www.railsconf.com|107.20.162.205|:80... connected.
    HTTP request sent, awaiting response... 200 OK
    Length: unspecified [text/html]
    Saving to: ‘talks’
    [ <=> ] 74,321 258KB/
    s in 0.3s
    2013-04-27 21:04:25 (258 KB/s) - ‘talks’ saved [74321]
    /tmp ᐅ du -hs talks
    76K talks
    /tmp ᐅ gzip talks
    /tmp ᐅ du -hs talks.gz
    28K talks.gz
    /tmp ᐅ
    

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97. /tmp ᐅ du -hs talks.gz
    28K talks.gz
    28K * 10,000,000 = 0,26 TB
    

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98. 28K * 10,000,000 = 0,26 TB
    Harddrive space is cheap.
    By saving the files non-gz and using
    a data deduplication file system you
    just need 5-10% of the 0,26 TB.
    Nginx can gzip the files on the fly.
    

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99. Nginx will happily read a
    cookie and find the pre-
    rendered page in a given
    directory structure.
    

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100. Warning: To setup a complex
     page_cache system is a lot of
     work. You have to tackle not only
     Rails but nginx too. It does increase
     the snappiness of your application
     but might not be worth the effort
     for small systems.
     

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101. 0
     30
     60
     90
     120
     Vanilla Fragment Caching HTTP Cache Preheater Page Caching
     19 s
     Any chance to
     get a single
     digit here?
     

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102. Add Ember.js to your software stack!
     http://emberjs.com
     rails new testapp -m http://emberjs.com/edge_template.rb
     

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103. 0
     37,5
     75
     112,5
     150
     Vanilla Fragment CachingHTTP Cache Preheater Page Caching Ember.js
     8 s
     14.5 x faster!
     

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104. What to do with
     your application?
     

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105. Existing applications:
     Go for the low hanging
     fruits fragment caching
     and HTTP caching.
     

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106. New applications:
     Learn Ember.js and
     combine it with Rails.
     But don‘t forget HTTP
     caching.
     To learn more about Ember: Come to my
     Ember.js talk at 17:00 in room New York I.
     

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107. Thank you!
     stefan.wintermeyer@amooma.de
     @wintermeyer
     Contact me if
     you need an
     performance
     audit of your
     existing Web
     application.
     

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