Monkey-patch for Delayed::Job's MySQL reserve strategy

patch_delayed_job_reserve_strategy.rb

require 'delayed_job_active_record'

module Delayed
  module Backend
    module ActiveRecord
      class Job
        # override UPDATE..LIMIT strategy
        # see https://github.com/collectiveidea/delayed_job_active_record/issues/63#issuecomment-26284690
        def self.reserve(worker, max_run_time = Worker.max_run_time)
          ready_scope = self.ready_to_run(worker.name, max_run_time)
          ready_scope = ready_scope.where('priority >= ?', Worker.min_priority) if Worker.min_priority
          ready_scope = ready_scope.where('priority <= ?', Worker.max_priority) if Worker.max_priority
          ready_scope = ready_scope.where(:queue => Worker.queues) if Worker.queues.any?
          ready_scope = ready_scope.by_priority

          now = self.db_time_now
          ready_scope.limit(worker.read_ahead).detect do |job|
            count = ready_scope.where(:id => job.id).update_all(:locked_at => now, :locked_by => worker.name)
            count == 1 && job.reload
          end
        end
      end
    end
  end
end

May I promote collectiveidea/delayed_job_active_record#89, which would make things a bit easier

And if you just want to use the default method:

module Delayed
  module Backend
    module ActiveRecord
      class Job
        class << self
          alias_method :reserve_with_scope, :reserve_with_scope_using_default_sql
        end
      end
    end
  end
end