Wolox on Rails - Batchifier

Gem that allows you to easily divide processing or requests that work with a lot of information into several batches with smaller chunks of data, taking care of the result from each one and providing it joint together based on different strategies for parsing said response.

Add this line to your application's Gemfile:

gem 'wor-batchifier'

And then execute:

$ bundle

Or install it yourself as:

$ gem install wor-batchifier

The first step is to include the Wor::Batchifier in the Class or Module you intend to use it:

class MyClass
  include Wor::Batchifier
end

If you're going to use the gem in your controllers, a good practice would be to define a parent controller from which all other controllers will have to extend to have access to the batchifier's methods. So, let's do that in our ApplicationController.rb:

class ApplicationController < ActionController::Base
  include Wor::Batchifier
end

You could also include the batchifier just in the controllers you intend to use it in.

The final step, is to find any request or process you wish to perform with smaller chunks of data and utilize the batchifier's methods to divide it into smaller tasks.

For example, let's pretend we have an endpoint called bulk_request that communicates with a third API and sends a lot of information to be utilized.

def bulk_request
  ThirdAPI.bulk_request(params[:information])
end

Now we will partition that request into chunks using the batchifier as to not overburden the ThirdAPI:

def bulk_request
  execute_in_batches(params[:information], batch_size: 100, strategy: :add) do |chunks|
    ThirdAPI.bulk_request(chunks)
  end
end

The batchifier will take three parameters, the first one being the information that needs to be partitioned, then the batch_size we wish to utilize and finally the symbol of the strategy that will be implemented on the response of each batch.

• Add: For each request, it joins together each response no matter the result.
• Maintain-Unique: It will only add the results that are not present already in the response.
• No-Response: It will not provide any response whatsoever.

Should you desire to add new strategies, it's as simple as creating a new class and defining a method called merge_strategy which will hold the logic that will be implemented to parse and merge the results from each batch. Let's look at an example:

module Wor
  module Batchifier
    class MaintainUnique < Strategy
      def merge_strategy(response,memo)
        return response.merge(memo) { |_, v1, _| v1 }
      end
    end
  end
end

The merge_strategy will receive two parameters, the first being "response" which is the total response which will be returned from execute_in_batches, and "memo" is the recursive response from each batch that will be added to response in each iteration. If you want to merge or do something else entirely, you have the option to do so.

All strategies have a base_case which by default is an empty hash {} but if you wish to override it, you can define your own in your strategy by simply adding a method called base_case which should return the value you desire for your own personal needs.

def base_case
 # An initial step or value where the responses will be merged to.
end

The new class that will hold the method merge_strategy should inherit the class Strategy. If the strategy doesn't define the method, an exception will be raised when trying to utilize it warning that it does not respect the contract set by the Strategy Interface.

You can also define a merge strategy via Proc, without the need of creating a new class. The Proc should receive two parameters: the first being "response" and the second one being "memo", both of which work the same way as they do when you create a class and define its merge strategy. All Procs have {} as their base case which cannot be changed. Let's look at an example:

merge_strategy = Proc.new do |response, memo|
  memo = [] if memo.empty?
  memo + response
end

execute_in_batches(collection, batch_size: 10, strategy: merge_strategy) do |chunk|
  ...
end

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Run rubocop lint (rubocop -R --format simple)
5. Run rspec tests (bundle exec rspec)
6. Push your branch (git push origin my-new-feature)
7. Create a new Pull Request

This project was developed by Pedro Jara along with Diego Raffo at Wolox.

Maintainers: Pedro Jara, Federico Volonnino

Contributors: Pedro Jara, Federico Volonnino

wor-batchifier is available under the MIT license.

Copyright (c) 2017 Wolox

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