caching.rb

class AbstractDimensionTable
  def self.call_remote_cache(fields)
    Cache.fetch(table_name, fields) do
      call_redshift fields
    end
  end
end

class Cache
  def self.fetch(table_name, fields, &block)
    # Try going to redis first
    # If there is no value in there, call the block that was passed in
    # If a value comes back from the block, add it to the cache and return value

    result = redis.get(table_name + ':' + fields.values.join('|'))

    unless result
      result = block.call

      unless result.nil?
        redis.set(table_name + ':' + fields.values.join('|'), result)
      end
    end

    # An 'empty' result from Redshift will be nil,
    # But an 'empty' result from Redis is an empty string
    # Return nil in either case
    !result || result.empty? ? nil : result
  end