Resque Data Warehouse
A Resque plugin. Requires Resque 1.9.10.
resque-data-warehouse allows you to use Redis to queue up and then Resque to process transactions on transaction-heavy tables that need to be replicated on other tables optimized for reporting.
Transactions for a given object (classname + ID) are queued up behind a Redis key, and then processed using Resque jobs. If load is low, each transaction will be processed almost immediately after it occurs; at higher loads, multiple transactions will queue up before the Resque job gets to them, and then only the last transaction will be applied to the data warehousing table, thus minimizing database load and dynamically adjusting the delay in the copy to match the current load.
This only works with Rails; it has only been tested with Rails 2.3.4 in which case the after_commit gem is also required.
Usage / Examples
Suppose you have a database class Transactional, that gets a lot of traffic, and you want to have a counterpart to this class, TransactionalFact, in a data warehouse. All you need to do are the following:
- Create an ActiveRecord model named TransactionalFact, with all the instance variables you want in it.
- Add a method to TransactionalFact named execute_transaction, which assumes that all the fields in the fact that match the original Transactional are already set, saves them, and then performs any additional logic (denormalization, etc.) to update any remaining fields.
- Require 'resque-data-warehouse' in Transactional, and add a line "warehoused".
Very simple examples of both classes:
class Transactional < ActiveRecord::Base require 'resque-data-warehouse' warehoused end class TransactionalFact < ActiveRecord::Base def execute_transaction self.save # Any additional logic here end end
Customize & Extend
No customizations are available right now, but some obvious ones (such as how to derive the name of the warehoused class) are likely to occur soon.
As a gem
$ gem install resque-data-warehouse
In a Rails app, as a plugin
$ ./script/plugin install git://github.com/Mechaferret/resque-data-warehouse.git
Thanks to resque and Redis for making this work possible.