celery初级教程(七)

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本文介绍如何使用Celery配置并执行周期性任务。通过示例展示了如何设置Celery Beat Schedule来定时运行任务，包括固定间隔和基于Cron表达式的复杂调度。

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我们如何使用celery执行一些周期性任务呢？

celery beat是一个调度器，它可以周期内指定某个worker来执行某个任务。如果我们想周期执行某个任务需要增加beat_schedule配置信息.

celeryconfig.py配置信息如下：

ROKER_URL = 'redis://:332572@127.0.0.1:6379/1'

CELERY_RESULT_BACKEND = 'redis://:332572@127.0.0.1:6379/2'

CELERYBEAT_SCHEDULE = {
    'every-5-minute':
        {
            'task': 'proj.tasks.period_task',
            'schedule': 5.0,
            'args': (16, 16),
        }
}

CELERY_ROUTES = ({
    'proj.tasks.send_email': {'queue': 'queue1'},
    'proj.tasks.upload_file': {'queue': 'queue1'},
    'proj.tasks.image_process': {'queue': 'queue2'},
    },
    # route_for_task,
)

CELERYBEAT_SCHEDULE配置每隔5秒执行一次period_task任务, 'every-5-minute'为任务名称，可自定义。task指定周期执行的任务函数，schedule指定多久执行一次task任务， args为传递给任务函数的参数。

tasks.py模块内容如下:

from proj.celery import app as celery_app
import time

# 创建任务函数
@celery_app.task
def send_email():
    print("正在发送email....")
    time.sleep(5)
    print("email发送完毕!")

@celery_app.task
def upload_file():
    print("正在处理文件上传任务....")
    time.sleep(3)
    print("文件上传完毕!")

@celery_app.task
def image_process():
    print("正在处理图像....")
    time.sleep(5)
    print("图像处理完毕!")

@celery_app.task
def period_task(a, b):
    print("开始周期性任务...")
    time.sleep(3)
    print("周期性任务执行完毕:%d!" % (a + b))

启动woker处理周期性任务:

celery -A proj worker --loglevel=info --beat

在命令后面加上--beat,表示启动周期性任务。

如果我们想指定在某天某时某分某秒执行某个任务，可以执行cron任务, 增加配置信息如下:

CELERYBEAT_SCHEDULE = {
    'every-5-minute':
        {
            'task': 'proj.tasks.period_task',
            'schedule': 5.0,
            'args': (16, 16),
        },
    'add-every-monday-morning': {
        'task': 'proj.tasks.period_task',
        'schedule': crontab(hour=7, minute=30, day_of_week=1),
        'args': (16, 16),
    },

}

crontab编写的例子:

例子	含义
`crontab()`	每分钟执行
`crontab(minute=0, hour=0)`	Execute daily at midnight.
`crontab(minute=0, hour='*/3')`	Execute every three hours: midnight, 3am, 6am, 9am, noon, 3pm, 6pm, 9pm.
`crontab(minute=0,` `hour='0,3,6,9,12,15,18,21')`	Same as previous.
`crontab(minute='*/15')`	Execute every 15 minutes.
`crontab(day_of_week='sunday')`	Execute every minute (!) at Sundays.
`crontab(minute='',` `hour='',` `day_of_week='sun')`	Same as previous.
`crontab(minute='*/10',` `hour='3,17,22',day_of_week='thu,fri')`	Execute every ten minutes, but only between 3-4 am, 5-6 pm, and 10-11 pm on Thursdays or Fridays.
`crontab(minute=0, hour='/2,/3')`	Execute every even hour, and every hour divisible by three. This means: at every hour except: 1am, 5am, 7am, 11am, 1pm, 5pm, 7pm, 11pm
`crontab(minute=0, hour='*/5')`	Execute hour divisible by 5. This means that it is triggered at 3pm, not 5pm (since 3pm equals the 24-hour clock value of “15”, which is divisible by 5).
`crontab(minute=0, hour='*/3,8-17')`	Execute every hour divisible by 3, and every hour during office hours (8am-5pm).
`crontab(0, 0, day_of_month='2')`	Execute on the second day of every month.
`crontab(0, 0,` `day_of_month='2-30/3')`	Execute on every even numbered day.
`crontab(0, 0,` `day_of_month='1-7,15-21')`	Execute on the first and third weeks of the month.
`crontab(0, 0, day_of_month='11',` `month_of_year='5')`	Execute on the eleventh of May every year.
`crontab(0, 0,` `month_of_year='*/3')`	Execute on the first month of every quarter.

开启一个celery beat服务：

celery -A proj beat

celery需要保存上次任务运行的时间在数据文件中，文件在当前目录下名字叫celerybeat-schedule. beat需要访问此文件：

celery -A proj beat -s /home/celery/var/run/celerybeat-schedule