Scheduling remote cronjobs

A common requirement is to perform some task at a given time every day or week automatically. Modal facilitates this through function schedules.

Basic scheduling

Let’s say we have a Python module heavy.py with a function, perform_heavy_computation().

# heavy.py
def perform_heavy_computation():
    ...

if __name__ == "__main__":
    perform_heavy_computation()

To schedule this function to run once per day, we create a Modal Stub and attach our function to it with the @stub.function decorator and a schedule parameter:

# heavy.py
import modal
stub = modal.Stub()

@stub.function(schedule=modal.Period(days=1))
def perform_heavy_computation():
    ...

To activate the schedule, deploy your app, either through the CLI:

modal app deploy --name daily_heavy heavy.py::stub

Or programmatically:

if __name__ == "__main__":
    stub.deploy("daily_heavy")

When you make changes to your function, just rerun the deploy command to overwrite the old deployment.

Monitoring your scheduled runs

To see past execution logs for the scheduled function, go to the Deployments section on the Modal web site.

Schedule types

There are two kinds of base schedule values - modal.Period and modal.Cron.

modal.Period lets you specify an interval between function calls, e.g. Period(days=1) or Period(hours=5):


# runs once every 5 hours
@stub.function(schedule=modal.Period(hours=5))
def perform_heavy_computation():
    ...

modal.Cron gives you finer control using cron syntax:

# runs at 8 am (UTC) every Monday
@stub.function(schedule=modal.Cron("0 8 * * 1"))
def perform_heavy_computation():
    ...

For more details, see the API reference for Period, Cron and Function