Delayed Job Background Notification modification

delayed_job_config.rb

# copy to: config/initializers/delayed_job_config.rb

# Fail at startup if method does not exist instead of later in a background job
[[ExceptionNotifier::Notifier, :background_exception_notification]].each do |object, method_name|
  raise NoMethodError, "undefined method `#{method_name}' for #{object.inspect}" unless object.respond_to?(method_name, true)
end

# Chain delayed job's handle_failed_job method to do exception notification
Delayed::Worker.class_eval do
  def handle_failed_job_with_notification(job, error)
    handle_failed_job_without_notification(job, error)
    # only actually send mail in production
    if Rails.env.production?
      # rescue if ExceptionNotifier fails for some reason
      begin
        failing_method = job.handler.scan(/method_name: .*/).try(:first)
        failing_db_object = job.handler.scan(/(?:id: )(.*)/).try(:first).try(:first)
        ExceptionNotifier::Notifier.background_exception_notification(error, data: {failing_method: failing_method,
                                                                                    first_failing_db_object: failing_db_object,
                                                                                    job: job, handler: job.handler, last_error: job.last_error}).deliver
      rescue Exception => e
        # this means we can debug by referring to the logs and searching for "ExceptionNotifier"
        Rails.logger.error "ExceptionNotifier failed: #{e.class.name}: #{e.message}"
        e.backtrace.each do |f|
          Rails.logger.error "  #{f}"
        end
        Rails.logger.flush
      end
    end
  end
  alias_method_chain :handle_failed_job, :notification
end

Delayed::Job.class_eval do
  scope :with_errors, where("last_error is NOT null")

  # Quickly see offending jobs
  class << self
    def show_errors(n)
      first(n).select.(&:last_error).map {|n| n.last_error.match(/^.*\n/)}
    end
    # Return array of jobs relating to a particular identifying_column
    # example: id_column = "subject_id" gets all the effected subjects
    def jobs_on_id_column(id_column)
      all.map {|j| j.handler.match(/#{id_column}: '(.*)'/).try :[], 1 }.compact.uniq
    end

    def clear_failed
      where("last_error is NOT null").destroy_all
    end
  end
end