Custom logging from firebase function

Solution 1:

OK, I finally tracked it down. According to this answer, the service account used by firebase functions is {project-id}@appspot.gserviceaccount.com, and in my project, that account did not have the 'Logs Writer' role. Adding that role solves the problem.

I find it odd that the firebase functions don't need that role to log messages using console.log(), but perhaps that call is intercepted by the functions environment, and the logs are written as a different service account. It also explains why the functions running locally were able to write the logs, as they run using the 'owner' service account, which has full access.