Why I hate Caching. And the Things I'm Trying to do to Change it.

Transcript

1. WHY I HATE CACHING
   AND THE THINGS I'M TRYING TO DO TO
   CHANGE IT
   @nettofarah
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2. nettofarah
   github.com/nettofarah
   @nettofarah
   http://bit.ly/kashmir-netto
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3. Senior Product Engineer @ IFTTT
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4. IFTTT
   Connect the Apps you Love
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5. IFTTT
   Millions of Users
   Website (desktop & mobile)
   8 Apps (IF & DO)
   Billions of Requests and Transactions
   every day
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6. Rails doesn't Scale
   Said someone in the Past. For whatever
   reason.
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7. Scaling Web (Rails) Apps
   You can do it!
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8. Background Jobs
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9. With a lot of Processes
   or
   With Threads
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10. Scaling Web (Rails) Apps
    with
    Rails.cache
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11. Easy and beautiful at first
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12. Incredibly tricky after some time
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13. Caching is like Cocaine
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14. What is Caching Anyway?
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15. The 2 Hardest Problems in
    Computer Science
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16. Cache Invalidation
    and
    Naming Things
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17. Ok, so you're still not convinced
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18. Oops, we forgot to remove it from
    the cache
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19. Just ask them to clear the browser
    cache
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20. Oh, that number is off because of
    our cache
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21. No worries, our cache should be
    clear in about 4 hours
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22. Oh shoot! I forgot to add the line
    that removes it from the cache
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23. Which leads to frustration...
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24. 24 / 65
    

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25. 25 / 65
    

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26. 26 / 65
    

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27. class: fake-middle, no-logo, image
    background-image: url(images/cache1.png)
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28. And Some other design problems
    like
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29. Cache Invalidation in callback hooks
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30. Inconsistent TTLs
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31. Inconsistent Cache Keys
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32. Nested Caching
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33. N+1 Queries
    from cache
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34. Unrealistic Experience
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35. What happens if your cache box
    dies?
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36. I'm not saying you should abandon
    caching altogether
    But maybe there is a better way
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37. What if I told you
    That some times looking up memcached
    could be slower than performing a lookup in
    your database
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38. Step 0
    Understand your bottlenecks
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39. Most performance challenges are IO
    bound
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40. That might not be true sometimes,
    though
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41. Step 1
    Understand your Database
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42. EXPLAIN and SLOW LOG
    are your best friends
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43. Spend some time analyzing your
    indexes
    specially compound ones
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44. Search Engines (SOLR,
    ElasticSearch)
    Try and understand how indexes are
    constructed. When commit operations are
    performed, analyze your indexes at
    write and read time.
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45. Redis
    SLOWLOG can save you
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46. Step 2
    Use the best tool for the job
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47. Still not convinced?
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48. How to Cache?
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49. HTTP Caching
    My favorite kind. If used wisely.
    Headers
    Varnish / Instart Logic
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50. Template Caching
    IMO, Doesn't sound like a great practice.
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51. Controller Caching
    Very tricky and when it comes to state.
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52. Model Caching
    Hard to design
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53. 53 / 65
    

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54. class Person
    include Kashmir
    def initialize(name, age)
    @name = name
    @age = age
    end
    representations do
    rep :name
    rep :age
    end
    end
    Person.new('Netto Farah', 27).represent(:name, :age)
    => {:name=>"Netto Farah", :age=>"27"}
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55. class Recipe < OpenStruct
    include Kashmir
    representations do
    rep(:title)
    rep(:chef)
    end
    end
    class Chef < OpenStruct
    include Kashmir
    representations do
    rep(:name)
    end
    end
    netto = Chef.new(
    name: 'Netto Farah'
    )
    beef_stew = Recipe.new(
    title: 'Beef Stew',
    chef: netto
    )
    beef_stew.represent(
    :title,
    { :chef => :name }
    )
    => {
    :title => "Beef Stew",
    :chef => {
    :name => 'Netto Farah'
    }
    }
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56. And Many More Examples
    https://github.com/IFTTT/kashmir
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57. Cache Layers
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58. 58 / 65
    

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59. Database Query Planner
    Levarages
    ActiveRecord::Associations::Preloader
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60. Prevents N+1 Queries
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61. Chef.all.each do |chef|
    chef.recipes.to_a
    end
    SELECT * FROM chefs
    SELECT "recipes".*
    FROM "recipes" WHERE "recipes"."chef_id" = 1
    SELECT "recipes".*
    FROM "recipes" WHERE "recipes"."chef_id" = 2
    ...
    SELECT "recipes".*
    FROM "recipes" WHERE "recipes"."chef_id" = N
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62. Chef.all.represent([:recipes])
    SELECT "chefs".* FROM "chefs"
    SELECT "recipes".* FROM "recipes"
    WHERE "recipes"."chef_id" IN (1, 2)
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63. Expiration
    Trickiest part.
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64. Advanced Use Cases
    Rest APIs
    GraphQL like endpoints
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65. Questions?
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