| 12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273747576777879808182838485 |
- ================
- Periodic Tasks
- ================
- You can schedule tasks to run at intervals like ``cron``.
- Here's an example of a periodic task:
- .. code-block:: python
- from celery.decorators import periodic_task
- from datetime import timedelta
- @periodic_task(run_every=timedelta(seconds=30))
- def every_30_seconds(**kwargs):
- logger = self.get_logger(**kwargs)
- logger.info("Running periodic task!")
- If you want a little more control over when the task is executed, for example,
- a particular time of day or day of the week, you can use the ``crontab`` schedule
- type:
- .. code-block:: python
- from celery.task.schedules import crontab
- from celery.decorators import periodic_task
- @periodic_task(run_every=crontab(hour=7, minute=30, day_of_week=1))
- def every_monday_morning(**kwargs):
- logger = self.get_logger(**kwargs)
- logger.info("Execute every Monday at 7:30AM.")
- The syntax of these crontab expressions is very flexible. Some examples:
- +-------------------------------------+--------------------------------------------+
- | **Example** | **Meaning** |
- +-------------------------------------+--------------------------------------------+
- | crontab() | Execute every minute. |
- +-------------------------------------+--------------------------------------------+
- | crontab(minute=0, hour=0) | Execute daily at midnight. |
- +-------------------------------------+--------------------------------------------+
- | crontab(minute=0, | Execute every three hours---at midnight, |
- | | 3am, 6am, 9am, noon, 3pm, 6pm, 9pm. |
- +-------------------------------------+--------------------------------------------+
- | crontab(minute=0, | Same as previous. |
- | hour=[0,3,6,9,12,15,18,21]) | |
- +-------------------------------------+--------------------------------------------+
- | crontab(minute="\*/15") | Execute every 15 minutes. |
- +-------------------------------------+--------------------------------------------+
- | crontab(day_of_week="sunday") | Execute every minute (!) at sundays. |
- +-------------------------------------+--------------------------------------------+
- | crontab(minute="*", | Same as previous. |
- | hour="*", | |
- | day_of_week="sun") | |
- +-------------------------------------+--------------------------------------------+
- | crontab(minute="\*/10", | Execute every ten minutes, but only |
- | hour="3,17,22", | between 3-4 am, 5-6 pm and 10-11 pm on |
- | day_of_week="thu,fri") | thursdays or fridays. |
- +-------------------------------------+--------------------------------------------+
- | crontab(minute=0, hour="\*/2,\*/3") | Execute every even hour, and every hour |
- | | divisable by three. This means: |
- | | at every hour *except*: 1am, |
- | | 5am, 7am, 11am, 1pm, 5pm, 7pm, |
- | | 11pm |
- +-------------------------------------+--------------------------------------------+
- | crontab(minute=0, hour="\*/5") | Execute hour divisable by 5. This means |
- | | that it is triggered at 3pm, not 5pm |
- | | (since 3pm equals the 24-hour clock |
- | | value of "15", which is divisable by 5). |
- +-------------------------------------+--------------------------------------------+
- | crontab(minute=0, hour="\*/3,8-17") | Execute every hour divisable by 3, and |
- | | every hour during office hours (8am-5pm). |
- +-------------------------------------+--------------------------------------------+
- If you want to use periodic tasks you need to start the ``celerybeat``
- service. You have to make sure only one instance of this server is running at
- any time, or else you will end up with multiple executions of the same task.
- To start the ``celerybeat`` service::
- $ celerybeat
- You can also start ``celerybeat`` with ``celeryd`` by using the ``-B`` option,
- this is convenient if you only have one server::
- $ celeryd -B
|
