使用 apscheduler 和 scrapy 做定时抓取爬虫为什么只抓取一次

from apscheduler.schedulers.background import BackgroundScheduler
from apscheduler.triggers.cron import CronTrigger
import time
from log.make_log import make_log_file

from scrapy.crawler import CrawlerProcess
from scrapy.utils.project import get_project_settings

from spider.spiders.aqi import AqiSpider

def aqi(crawler, spider):
    try:
        crawler.crawl(spider)
        crawler.start()
    except Exception, e:
        make_log_file(str(e),'scrapy')

if __name__ == '__main__':
    settings = get_project_settings()
    crawler = CrawlerProcess(settings)
    spider = AqiSpider()
    scheduler = BackgroundScheduler()
    scheduler.daemonic=False
    cron = CronTrigger(second='*/30')
    scheduler.add_job(aqi, cron, args=[crawler, spider])
    scheduler.start()
    while True:
        time.sleep(1000)