What is the chalice @app.schedule syntax for cron events?

Question

I am trying to follow the documentation from https://chalice.readthedocs.io/en/latest/topics/events.html

I tried this

@app.schedule('0 0 * * ? *')
def dataRefresh(event):
    print(event.to_dict())

and got this error:

botocore.exceptions.ClientError: An error occurred (ValidationException) when calling the PutRule operation: Parameter ScheduleExpression is not valid.

and so tried this:

@app.schedule(Cron('0 0 * * ? *'))
def dataRefresh(event):
    print(event.to_dict())

and got this other error:

NameError: name 'Cron' is not defined

Nothing works... what's the correct syntax?

Answer 1

If you want to use the Cron object you have to import it from the chalice package, and then each value is a positional parameter to the Cron object:

from chalice import Chalice, Cron

app = Chalice(app_name='sched')


@app.schedule(Cron(0, 0, '*', '*', '?', '*'))
def my_schedule():
    return {'hello': 'world'}

Here's the docs for Cron that has more info.

Or alternatively use this syntax, which works without the extra import:

@app.schedule('cron(0 0 * * ? *)')
def dataRefresh(event):
    print(event.to_dict())