How to create cron jobs in firebase programmatically

Question

I have a unique problem here. I actually need to schedule a task to send emails to eligible users at specific times. I have checked and found out that scheduling cron jobs c

Answer 1

Instead of trying to dynamically creating scheduled function, consider having a single function that runs on a fixed schedule, and then implementing your timing logic inside of that function.

So instead of saying "I need to schedule a function that runs 3 hours from now and send a message to these 5 people", think of it as a task that you can write into a database: "at x:yz send an email to these 5 people", and then have a periodic Cloud Function that checks what tasks it needs to execute.

Also see Delay Google Cloud Function, How to use scheduler for Firebase Cloud Functions with Realtime Database/Analytics triggers?

Alternatively you can use Cloud Scheduler to create a task for the specific action you want to perform, and then have it post to Cloud Functions via PubSub.

As an even newer alternative: Use a separate scheduler service that has an API to create schedules, like Cloud Tasks. Doug wrote a great article about that in How to schedule a Cloud Function to run in the future with Cloud Tasks (to build a Firestore document TTL).