background_job_watcher.rb

class BackgroundJobWatcher
  attr_accessor :mailer, :error_io

  class << self
    def attempt(job_name, &blk)
      new.attempt(job_name, &blk)
    end
  end

  def initialize(opts = {})
    self.mailer = opts.fetch(:mailer) { ErrorMailer }
    self.error_io = opts.fetch(:error_io) { $stderr }
  end

  def attempt(job_name, &blk)
    blk.call
  rescue => e
    msg = "#{e.message}\n\t#{e.backtrace.join("\n\t")}"
    error_io.puts msg
    mailer.notify("#{job_name} failed", msg)
  end
end

background_watcher_spec.rb

require 'spec_helper'
require 'stringio'

describe BackgroundJobWatcher do
  let(:error_io) { StringIO.new }
  let(:mailer) { double('Mailer').as_null_object }

  subject { BackgroundJobWatcher.new(:mailer => mailer, :error_io => error_io ) }

  describe '#attempt(description, &blk)' do
    it 'yields to block' do
      i = 0
      subject.attempt('foo') { i += 1 }
      i.should == 1
    end

    context 'on failure' do
      it 'rescues error' do
        subject.attempt('foo') { raise 'some error' }
      end

      it 'notifies mailer' do
        mailer.should_receive(:notify).with('myjob failed', instance_of(String))
        subject.attempt('myjob') { raise 'some error' }
      end

      it 'outputs message to error io' do
        subject.attempt('myjob') { raise 'some error' }
        error_io.string.should include('some error')
      end
    end
  end
end

nightly.rb

ActiveRecord::Base.logger = Logger.new(STDOUT)

Cart.purge_stale(3)

Order.purge_unconfirmed(14)

ActionLogEntry.purge

Logging::ActionLogging.current_user = ::User.new(:login => 'kisbot')

BackgroundJobWatcher.attempt('nightly mailgun import') do
  MailerService.pull_bounces
  MailerService.pull_complaints
  MailerService.pull_unsubscribes
end