circle.yml

test:
    override:
      - "bundle exec bin/rubocop_parallel": { parallel: true }

rubocop_parallel

#!/usr/bin/env ruby

require 'rubocop'
require 'yaml'

Dir.chdir File.expand_path('../..', __FILE__)
config = YAML.load_file '.rubocop.yml'

files = Dir.glob '**/*.rb'
files += Dir.glob config['AllCops']['Include']
files -= Dir.glob config['AllCops']['Exclude']

files.sort!.uniq!

node = (ENV['CIRCLE_NODE_INDEX'] || 0).to_i
total = (ENV['CIRCLE_NODE_TOTAL'] || 1).to_i

files = files.select.with_index { |_file, i| i % total == node }

puts "Running RuboCop on node #{node + 1} of #{total}"

exit RuboCop::CLI.new.run(files)