Redis Storage

redis.rb

$redis = Redis.new(host: 'localhost', port: 6379, db: 1)

redis_json.rb

class RedisJSON < RedisStorage
  class << self
    def fetch(*args)
      key     = key(args)
      content = cache(key)

      content.nil? ? store(key, yield) : parse(content)
    end

    private

    def parse(content)
      JSON.parse(content)
    end
  end
end

redis_object.rb

class RedisObject < RedisStorage
  class << self
    def fetch(*args)
      key     = key(args)
      content = cache(key)

      if content.nil?
        content = Marshal.dump(yield)

        store(key, content)

        yield
      else
        parse(content)
      end
    end

    private

    def parse(content)
      Marshal.load(content)
    end
  end
end

redis_storage.rb

# Usage:
#
# RedisJSON.fetch(*key, &block)
# RedisObject.fetch(*key, &block)
#
# Dummy Example:
# class User < ActiveRecord::Base
#   def whoami
#     cache_object(:users, uid) do
#       self
#     end
#   end
#
#   def cache_object(*key, &block)
#     RedisObject.fetch(*key, &block)
#   end
# end
#
# > user = User.first
# > user.id
# => 1
# user.whoami
# => #<User id: 1, ... >
# Marshal.load($redis.get("users:1"))
# => #<User id: 1, ... >


class RedisStorage
  class << self
    def fetch
      fail NotImplementedError, "This #{self.class} cannot respond to:"
    end

    private

    def default_expiration
      302400
    end

    def cache(key)
      $redis.get(key)
    end

    def store(key, content)
      $redis.set(key, content)
      $redis.expire(key, default_expiration)

      store_key(key)

      content
    end

    def get_keys(index)
      map = get_map(index)

      $redis.smembers(map)
    end

    def store_keys(*keys)
      keys.each { |key| store_key(key) }
    end

    def store_key(key)
      index = get_index(key)
      map   = get_map(index)

      $redis.sadd(map, key)
    end

    def delete_keys(index)
      keys = get_keys(index)
      map  = get_map(index)

      keys.each { |key| delete_key(key) }

      delete_key(map)
    end

    def delete_key(key)
      $redis.del(key)
    end

    def key(*args)
      args.compact.join(':')
    end

    def get_map(index)
      "#{index}:keys"
    end

    def get_index(key)
      key.split(':').first
    end
  end
end