Cache Key Versioning in Rails

cache_key_with_version is a method used in Ruby on Rails to generate a cache key for a model object that includes its version number. This method is helpful for ensuring cache consistency, as it combines the object’s unique ID, updated timestamp, and a version number to create a unique cache key.

How it Works

The cache_key_with_version method is available in Rails models that include ActiveRecord::Base. It generates a cache key by combining:

  1. Model Name: The name of the model.
  2. ID: The primary key of the record.
  3. Updated Timestamp: The timestamp of the last update to the record.
  4. Record Version (if available): The version number of the record, if your model has a lock_version column or any other versioning system implemented.

Example Usage

Suppose you have a Post model in your Rails application:

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class Post < ApplicationRecord
  # Assume this model has attributes: id, title, body, updated_at
end

You can generate a cache key for a post instance like this:

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post = Post.find(1)
cache_key = post.cache_key_with_version
puts cache_key

This will output something like:

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"posts/1-20240805123045678"

Benefits

Custom Cache Key

You can customize the cache key further by overriding the cache_key_with_version method in your model:

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class Post < ApplicationRecord
  def cache_key_with_version
    "#{model_name.cache_key}/#{id}-#{updated_at.to_s(:nsec)}-#{version_number}"
  end

  private

  def version_number
    # Custom logic to determine the version number
    lock_version || 1
  end
end

This customization allows you to include additional logic or attributes to be part of the cache key, making it more specific to your application’s requirements.

The cache_key_with_version method is a powerful tool in Rails for managing cache keys with versioning, providing automatic cache invalidation and ensuring that cached data is always up-to-date. If your models have a lock_version column, this method automatically incorporates it, further enhancing cache consistency.