invoice_charge_worker.rb

class InvoiceChargeWorker
  include TResque::Worker
  inputs :invoice_id

  worker_lock :to_id

  def work
    return unless needed?
    invoice.charge!
  end

  def to_id
    invoice.to_id
  end

  def needed?
    invoice.pending?
  end

  def invoice
    @invoice ||= Invoice.find(invoice_id)
  end
end