batch parallel processing

batch.rb

jobs_per_process = 100
process_count = 20

HolidayCampaignBidLapse.where('user_id % 2 = 0').where(sent: false).find_in_batches(batch_size: jobs_per_process * process_count) do |group|
  batches = group.in_groups(process_count)

  batches.each do |batch|
    Process.fork do
      ActiveRecord::Base.establish_connection
      batch.each do |campaign|
        credit = HolidayCreditBidLapse.find_or_create_by_user_id(campaign.user_id, :amount => 5)
        campaign.update_column :sent, true
      end
    end
  end
  Process.waitall
  return if HolidayCreditBidLapse.count >= 300000
end

# Watch send rate
loop do; sleep 1.minute; puts HolidayCreditBidLapse.count end