Introduction

Reasonable use of caching can greatly improve a website’s performance, making it an indispensable part of performance optimization.

Caching

  • Model-layer caching

    Through manual configuration, you can store selected query results in the corresponding cache system.

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    Rails.cache.fetch('all_products', expires_in: 1.days) do 
      Product.all.to_a
    end

    Make sure to verify that the returned result is the final result set.

  • Controller-layer caching

    • Action caching

      Caches the Action response, implemented with the help of Fragment Cache and callbacks.

      Various verification mechanisms can be added via before_action.

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      before_action :authentication, only: :show
      cache_action :show, expires_in: 1.hour

      This method was removed in Rails 4, but it can be re-enabled through a Gem.

    • Page caching

      Caches the page as a static page; it cannot perform authentication or similar checks.

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      class ProductsController < ActionController
        caches_page :index
      end

      This method was removed in Rails 4, but it can be re-enabled through a Gem.

  • View-layer caching

    • Fragment Cache

      As a page becomes more complex, full-page caching is no longer feasible; the page must instead be split into different fragments.

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      - cache('xxx' , expires_in: 1.days ) do 
        %ul
          = @product.name

      Fragment caching can be nested to form a special pattern known as Russian Doll Caching.

  • SQL caching

    This is a built-in feature of the Rails framework; it caches the result set of each query.

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    class ProductsController < ActionController
      def index
        # First Query
        @products = Product.all
      
        # Second Query (Cache)
        @products = Product.all
      end

    When the second query runs, it reads the result set cached in memory by the first query directly.

    Tips: The cache is valid for the lifetime of the action.

Configuration

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# Enable caching
config.action_controller.perform_caching = true
# Cache store backend
config.cache_store = :memory_store  # memory_store mem_cache_store file_store