Lightweight scheduler for python asyncio

Based on croniter to support the crontab syntax.

Installation

Installing acron.

$ pip install acron

Usage

To get started you need at least one job. Use the top level acron.run function for simple scheduling. Use SimpleJob to run a simple async function with no associated data.

import asyncio
import acron

async def do_the_thing():
    print("Doing the thing")

do_thing = acron.SimpleJob(
    name="Do the thing",
    schedule="0/1 * * * *",
    func=do_the_thing,
)

asyncio.run(acron.run({do_thing}))

For more advanced use cases, the Scheduler class can be used as async context manager. Call scheduler.wait() to keep it running forever. To submit jobs call scheduler.update_jobs(jobs) with the complete set of jobs.

Running an example Job running a function with associated data every hour...

import asyncio
import dataclasses

from acron.scheduler import Scheduler, Job

@dataclasses.dataclass(frozen=True)
class ThingData:
    foo: bool

async def do_the_thing(data: ThingData):
    print(f"Doing the thing {data}")

async def run_jobs_forever():
    do_thing = Job[ThingData](
        name="Do the thing",
        schedule="0/1 * * * *",
        data=ThingData(True),
        func=do_the_thing,
    )

    async with Scheduler() as scheduler:
        await scheduler.update_jobs({do_thing})
        await scheduler.wait()

if __name__ == "__main__":
    try:
        asyncio.run(run_jobs_forever())
    except KeyboardInterrupt:
        print("Bye.")

Specifying a timezone

For python 3.9+ you can use the standard library's zoneinfo module to specify a timezone.

import zoneinfo

async with Scheduler(tz=zoneinfo.ZoneInfo("Europe/Berlin")) as scheduler:
    ...

For earlier python versions you can use a third party library like pytz.

import pytz

async with Scheduler(tz=pytz.timezone("Europe/Berlin")) as scheduler:
    ...

Job context

It is possible to retrieve the context for the scheduled job from the running job function using job_context(). This returns a JobContext containing a reference to the ScheduledJob. The job_context() function is implemented using contextvars to provide the correct context to the matching asyncio task.

async def my_job_func():
    job_id = acron.job_context().scheduled_job.id
    job_name = acron.job_context().scheduled_job.job.name
    print(f"Running job {job_id!r}, scheduled with id {job_id}")

Local development

The project uses poetry to run the test, the linter and to build the artifacts.

The easiest way to start working on acron is to use docker with the dockerfile included in the repository (manual usage of poetry is explained here: https://python-poetry.org/docs/ ).

To use docker, first generate the docker image. Run this command from the top level directory in the repository:

docker build -t acron-builder -f docker/Dockerfile .

Now you can use it to build or run the linter/tests:

$ alias acron-builder="docker run --rm -it -v $PWD/dist:/build/dist acron-builder"

$ acron-builder run pytest tests
=============================================================================================== test session starts ================================================================================================
platform linux -- Python 3.9.7, pytest-5.4.3, py-1.10.0, pluggy-0.13.1
rootdir: /build
plugins: asyncio-0.15.1
collected 4 items
tests/test_acron.py ....                                                                                                                                                                                     [100%]
================================================================================================ 4 passed in 0.04s =================================================================================================

$ acron-builder build
Building acron (0.1.0)
  - Building sdist
  - Built acron-0.1.0.tar.gz
  - Building wheel
  - Built acron-0.1.0-py3-none-any.whl

$ ls dist
acron-0.1.0-py3-none-any.whl  acron-0.1.0.tar.gz

Debugging

Debug logging can be enabled by setting the ACRON_DEBUG environment variable to TRUE.