How do Firebase Cloud Functions ack Cloud pub/sub

Question

In this article on Google Cloud Pub Sub we are told that a function must return a status to ack receipt of a message. I have one question related specifically to Firebase Cloud Functions pubsub triggers:

I cannot see in the document above how or if a Firebase Cloud function acks the pub sub. Can someone explain this please?

Answer 1

This is implemented in Google-managed code. It’s effectively the same as a Pub/Sub push subscription, where a 200 response acks the message (https://cloud.google.com/pubsub/docs/push#receive_push). This auto-ack happens after your function finishes successfully.