invoice_charge_worker.rb

class InvoiceChargeWorker
  include TResque::Worker
  inputs :invoice_id

  worker_lock :invoice_id

  def self.process_all!
    Invoice.where(stat: 'pending').find_each do |invoice|
      self.enqueue(invoice_id: invoice.id)
    end
  end

  def work
    return unless needed?
    invoice.charge!
  end

  def needed?
    invoice.pending?
  end

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

# process all pending invoices
InvoiceChargeWorker.process_all!