Aila!.. Caching in Rails.

I will be speaking on why caching is important and how we can scale up the Rails app using different caching strategies like page, action & fragment. I will also speak on how we can improve the performance in the simplest way by using instance variable caching for expensive command’s result.

Transcript

1. RAILS
   AILA!.. CACHING IN
   

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2. Santosh Wadghule
   Freelancer
   http://mechanicles.com
   github.com/mechanicles
   twitter.com/mechanicles
   

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3. Food Lover
   

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4. Stay under 250ms to feel your app “fast”
   Stay under 1000ms to keep your users
   

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5. Caching
   

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6. Caching
   It is a process of storing data so future requests
   for that data can be served faster
   

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7. Caching
   It is a process of storing data so future requests
   for that data can be served faster
   Improves user experience
   

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8. Caching
   It is a process of storing data so future requests
   for that data can be served faster
   Saves a lot money and other hardwares
   Improves user experience
   

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9. Caching
   It is a process of storing data so future requests
   for that data can be served faster
   Saves a lot money and other hardwares
   Keeps you and your users happy :)
   Improves user experience
   

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10. Main Resource
    Cache Memory
    Client
    A A
    A
    A
    A
    Main Resource
    Cache Memory
    Requester
    A
    A
    A A
    A
    First
    Request
    Future
    Requests
    

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11. Web Cache
    

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12. BROWSER
    PROXY
    CDN
    RAILS APP
    REVERSE PROXY
    Components which
    support Web Cache
    

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13. Stop!
    Caching is not always a good way to make your app fast
    

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14. Think!
    Why your app is slow?
    

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15. CACHING IN RAILS
    BEFORE CACHING: FIRST BOOST YOUR RAILS APP
    ▸ Avoid n+1 queries.
    ▸ Index on foreign keys.
    ▸ Instance variable caching
    ▸ Load only required JavaScript files in web pages.
    ▸ Minify and ZIP stylesheets and JavaScript files.
    

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16. There are only two hard
    things in Computer Science:
    cache invalidation & naming
    things
    Phil Karlton
    CACHING IN RAILS
    

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17. Caching in Rails
    

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18. CACHING IN RAILS
    CACHING IN RAILS
    ▸ Basic Caching (Page, Action & Fragment Caching)
    ▸ Low Level Caching
    ▸ Alternative cache stores
    ▸ SQL Caching
    ▸ Conditional GET support
    

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19. Setting up caching in Rails
    

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20. CACHING IN RAILS
    SETTING UP CACHING IN RAILS
    ▸ `config.action_controller.perform_caching =
    true` for Rails 4
    ▸ Run `rake dev:cache` for Rails 5
    

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21. Page Caching
    

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22. CACHIN IN RAILS.
    PAGE CACHING
    ▸ Needs `actionpack-page_caching` gem
    

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23. APACHE
    PUMA
    CLIENT http:/example.com/posts/
    Without Caching
    

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24. APACHE
    PUMA
    CLIENT http:/example.com/posts/
    /public/posts.html
    Page Caching
    

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25. APACHE
    PUMA
    CLIENT http:/example.com/posts/
    /public/posts.html
    Page Caching
    

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27. class PagesController < ApplicationController
    def contact_us
    @contact = Contact.new
    end
    def about
    render
    end
    end
    

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28. ABOUT US PAGE RESPONSE WITHOUT CACHING
    Views have taken half a second
    

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29. class PagesController < ApplicationController
    caches_page :about
    def contact_us
    @contact = Contact.new
    end
    def about
    render
    end
    end
    

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30. ABOUT US PAGE RESPONSE WITHOUT CACHING
    Cached entire file in file system
    

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31. Response got served by web server for ‘About us’ page
    

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32. CACHING IN RAILS
    INVALIDATING PAGE CACHING
    ▸ Non model pages need to be deleted manually.
    ▸ expire_page helper method
    ▸ expire_page action: “index”
    ▸ expire_page action: “show”, id: @post
    ▸ ‘Sweepers’ also helps to invalidate the cache
    

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33. Action Caching
    

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34. CACHIN IN RAILS
    ACTION CACHING
    ▸ Needs `actionpack-action_caching` gem
    ▸ It uses fragment caching internally
    

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36. class HomeController < ApplicationController
    before_action :log_it
    def index
    if request.format.json?
    render json: { text: "Home Page" }
    else
    render
    end
    end
    private
    def log_it
    logger.info("")
    logger.info(">>>> BEFORE ACTION CODE <<<<")
    logger.info("")
    end
    end
    

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37. Home page response without caching
    

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38. class HomeController < ApplicationController
    before_action :log_it
    caches_action :index, if: Proc.new { !request.format.json? },
    expires_in: 30.seconds
    def index
    if request.format.json?
    render json: { text: "Home Page" }
    else
    render
    end
    end
    private
    def log_it
    logger.info("")
    logger.info(">>>> BEFORE ACTION CODE <<<<")
    logger.info("")
    end
    end
    

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39. Home page response while caching
    Fragment: views/localhost:3000/home/index
    Cache key : ‘views’ + ‘localhost:3000/home/index’
    

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40. Home page response with caching
    

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41. CACHING IN RAILS
    INVALIDATING ACTION CACHING
    ▸ expire_action helper method
    

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42. Fragment Caching
    

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44. 
    
    
    Name
    Amount
    
    
    
    <% @products.each do |product| %>
    <% cache(product) do %>
    
    
    <%= product.name %>
    
    
    <%= product.amount %>
    
    
    <%= link_to 'Edit ', edit_product_path(product) %>
    
    
    <% end %>
    <% end %>
    
    
    

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45. views/products/1-20160731074448006461000/2534a326647f6ea1c765472157da361f
    Cache Key
    timestamp (updated_at)
    product-id Cache Digest for dashboard page
    ‘cache(product) #=> product.cache_key’
    

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46. CACHIN IN RAILS.
    FRAGMENT CACHING
    ▸ `expire_fragment(‘name_of_cache’)` is also
    responsible to expire the fragment.
    ▸ `cache_if` & `cache_unless` for conditional fragment
    caching.
    

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47. Russian Doll Caching
    

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48. # product view template
    <% cache product do %>
    name: <%= product.name %>
    <%= render product.comments %>
    <% end %>
    # comment view template
    <% cache comment do %>
    <%= render comment %>
    <% end %>
    

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49. class Product < ActiveRecord::Base
    has_many :comments
    end
    class Comment < ActiveRecord::Base
    belongs_to :product, touch: true
    end
    

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50. Low Level Caching
    

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51. CACHIN IN RAILS.
    LOW LEVEL CACHING
    ▸ Uses `Rails.cache`API.
    

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52. App is damn slow when we fire request to Spark service to get the spark
    listings and we also sometimes get Spark API limit error.
    Issue
    

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53. class Listing < ApplicationRecord
    LIMIT = 20
    def self.spark_listings(page)
    SparkApi::ListingCart.listings(pagination: 1, page: page, limit: LIMIT)
    end
    end
    

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54. class Listing < ApplicationRecord
    LIMIT = 20
    def self.spark_listings(page)
    Rails.cache.fetch("spark_listing/page=#{page}", expires_in: 24.hours) do
    SparkApi::ListingCart.listings(pagination: 1, page: page, limit: LIMIT)
    end
    end
    end
    

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55. class Listing < ApplicationRecord
    LIMIT = 20
    def self.spark_listings(page)
    Rails.cache.fetch("spark_listing/page=#{page}", expires_in: 12.hours) do
    SparkApi::ListingCart.listings(pagination: 1, page: page, limit: LIMIT)
    end
    end
    end
    class Listing < ApplicationRecord
    LIMIT = 20
    def self.spark_listings(page)
    Rails.cache.fetch("spark_listing/page=#{page}", expires_in: 12.hours) do
    SparkApi::ListingCart.listings(pagination: 1, page: page, limit: LIMIT)
    end
    end
    end
    class Listing < ApplicationRecord
    LIMIT = 20
    def self.spark_listings(page)
    Rails.cache.fetch("spark_listing/page=#{page}", expires_in: 12.hours) do
    SparkApi::ListingCart.listings(pagination: 1, page: page, limit: LIMIT)
    end
    end
    end
    class Listing < ApplicationRecord
    LIMIT = 20
    def self.spark_listings(page)
    Rails.cache.fetch("spark_listing/page=#{page}", expires_in: 12.hours) do
    SparkApi::ListingCart.listings(pagination: 1, page: page, limit: LIMIT)
    end
    end
    end
    Saved money
    

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56. class Listing < ApplicationRecord
    LIMIT = 20
    def self.spark_listings(page)
    Rails.cache.fetch("spark_listing/page=#{page}", expires_in: 12.hours) do
    SparkApi::ListingCart.listings(pagination: 1, page: page, limit: LIMIT)
    end
    end
    end
    class Listing < ApplicationRecord
    LIMIT = 20
    def self.spark_listings(page)
    Rails.cache.fetch("spark_listing/page=#{page}", expires_in: 12.hours) do
    SparkApi::ListingCart.listings(pagination: 1, page: page, limit: LIMIT)
    end
    end
    end
    Saved money
    Saved response time as well
    

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57. class Listing < ApplicationRecord
    LIMIT = 20
    def self.spark_listings(page)
    Rails.cache.fetch("spark_listing/page=#{page}", expires_in: 12.hours) do
    SparkApi::ListingCart.listings(pagination: 1, page: page, limit: LIMIT)
    end
    end
    end
    Saved money
    Saved response time as well
    Awesome No?
    

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58. SQL Caching
    

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59. CACHIN IN RAILS.
    SQL CACHING
    ▸ Inbuilt Rails Feature
    ▸ SQL Caching will be valid per request
    ▸ DON’T NEED TO ANYTHING, Rails will take care of it
    

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60. Cache Stores
    

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61. CACHIN IN RAILS.
    CACHE STORES
    ▸ Cache stores - memory_store, file_store,
    mem_cache_store, null store, and user defined custom
    store
    ▸ By default file_store is enabled
    

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62. Cache Keys
    

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63. CACHIN IN RAILS.
    CACHE KEYS
    ▸ Hold any object which responds to either cache_key or
    to_param
    ▸ e.g. Rails.cache.read(site: "mysite", owners:
    [owner_1, owner_2])
    

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64. Conditional Get Support
    

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65. CACHIN IN RAILS.
    CONDITIONAL GET SUPPORT.
    ▸ Needs these headers HTTP_IF_NONE_MATCH &
    HTTP_IF_MODIFIED_SINCE to be set
    ▸ Sever matches these headers against Etag &
    last_modified respectively
    ▸ Rails provides `stale?` & `fresh_when` helpers
    

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66. class ProductsController < ApplicationController
    def show
    @product = Product.find(params[:id])
    fresh_when last_modified: @product.updated_at.utc, etag: @product
    end
    end
    

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67. This is all about Caching!
    

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68. Take Away
    At least use Fragment Caching and Conditional Get Support
    

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69. Thank You!
    santosh.wadghule@gmail.com
    @mechanicles
    

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