lib/delayed/job.rb
def run_with_lock(max_run_time, worker_name)
      logger.info "* [JOB] aquiring lock on #{name}"
      unless lock_exclusively!(max_run_time, worker_name)
        # We did not get the lock, some other worker process must have
        logger.warn "* [JOB] failed to aquire exclusive lock for #{name}"
        return nil # no work done
      end

      begin
        runtime =  Benchmark.realtime do
          invoke_job # TODO: raise error if takes longer than max_run_time
          destroy
        end
        # TODO: warn if runtime > max_run_time ?
        logger.info "* [JOB] #{name} completed after %.4f" % runtime
        return true  # did work
      rescue Exception => e
        reschedule e.message, e.backtrace
        log_exception(e)
        return false  # work failed
      end
    end
def run_with_lock(max_run_time, worker_name)
      logger.info "* [JOB] aquiring lock on #{name}"
      unless lock_exclusively!(max_run_time, worker_name)
        # We did not get the lock, some other worker process must have
        logger.warn "* [JOB] failed to aquire exclusive lock for #{name}"
        return nil # no work done
      end

      begin
        runtime =  Benchmark.realtime do
          invoke_job # TODO: raise error if takes longer than max_run_time
          destroy
        end
        # TODO: warn if runtime > max_run_time ?
        logger.info "* [JOB] #{name} completed after %.4f" % runtime
        return true  # did work
      rescue Exception => e
        reschedule e.message, e.backtrace
        log_exception(e)
        return false  # work failed
      end
    end
Try to run one job. Returns true/false (work done/work failed) or nil if job can't be locked.