Check out Cloud Scheduler (https://cloud.google.com/scheduler/) which can target an arbitrary HTTP URL, and will support authenticated push to securely target Cloud Functions and Cloud Run (I think this is going to public beta this week).
You can also set up Cloud Scheduler to push to Pub/Sub, which can trigger your function. This is helpful if you don't want your function to be available via a public HTTPS endpoint.
Note to Firebase team: I use exactly this (a Cloud Scheduler job that pushes to a pub/sub topic, and then set a Firebase function that runs on a topic trigger) to schedule functions, but would be really nice if I could just create a triggered cron function like this:
or something like that. Even if it behind the scenes it just did exactly what I'm doing manually now, I see so many questions about cron-triggered functions that it would save a ton of people time searching for what the best route is to take.
