An issue by arthurh4 at 2019-12-15 00:10:09+00:00
Original URL: zalando-incubator/kopf#271
 

Hello, very nice project ! I would like to run a function to run to some checks based on a timer (eg: every 30 seconds) is there any existing handler I could use ? Thanks

Commented by nolar at 2019-12-16 09:37:57+00:00
 

Hello. Thanks.

I'm currently working on this for #19, #150 and related issues, which will make it possible and easier. A draft is already functional, but I was slightly "distracted" by sickness.

Meanwhile, you can use this pattern:

import asyncio
import kopf

@kopf.on.create('zalando.org', 'v1', 'kopfexamples')
@kopf.on.resume('zalando.org', 'v1', 'kopfexamples')
def spawn_the_monitor(namespace, name, memo, logger, **kwargs):
    if not hasattr(memo, 'monitor'):
        memo.monitor = asyncio.create_task(monitor_me(namespace, name, logger))

@kopf.on.delete('zalando.org', 'v1', 'kopfexamples')
def stop_the_monitor(memo, **kwargs):
    if hasattr(memo, 'monitor'):
        memo.monitor.cancel()

async def monitor_me(namespace, name, logger):
    while True:
        logger.info('Checking...')
        # check it here (BEWARE: sync calls block the whole operator)
        await asyncio.sleep(30)

The same would be with the threading.Thread() and a sync-function, except that the thread is harder to terminate — needs an externally provided event-flag to indicate that it should stop (few more lines to the this example).

Commented by nolar at 2020-04-01 11:53:18+00:00
 

Daemons and timers are added in kopf>=0.27rc1.

Release notes:

• https://github.com/nolar/kopf/releases/tag/0.27rc1

Docs:

• https://kopf.readthedocs.io/en/latest/daemons/
• https://kopf.readthedocs.io/en/latest/timers/

Beware: the changes are quite massive, and the daemons/timers are a new feature, they are not tested thoroughly yet, can behave weird. Either test carefully in an isolated cluster/namespace, or wait for some time until the feature is tested by others (e.g. by us).

In your case, it would be:

import kopf

@kopf.timer(..., interval=30)
def fn(**kwargs):
    pass

For now, I close this issue as it is presumably solved. Any bugs or misbehaviour or misunderstanding should be reported separately.