python – apscheduler无法正常工作

#coding=utf-8
from apscheduler.scheduler import Scheduler
import logging

logging.basicConfig(filename='/tmp/log',level=logging.DEBUG,format='%(levelname)s[%(asctime)s]: %(message)s')

sched = Scheduler()
sched.start()

#@sched.interval_schedule(seconds=3)
def job_function():
    logging.debug('hello world')

sched.add_interval_job(job_function,seconds=3)

如果我切换到装饰器,仍然无法正常工作.日志是这样的：

DEBUG[2011-10-09 11:02:45,175]: Looking for jobs to run
DEBUG[2011-10-09 11:02:45,176]: No jobs; waiting until a job is added
INFO[2011-10-09 11:02:45,176]: Added job "job_function (trigger: interval[0:00:03],next run at: 2011-10-09 11:02:48.176444)" to job store "default"
INFO[2011-10-09 11:02:45,177]: Shutting down thread pool

添加了job job_function,但触发了神经,为什么？