Google cloud functions realtime database trigger setup in Python

Question

I am trying to setup a Google Cloud Function with a Firebase Realtime Database Trigger and cannot make the function to be triggered when I add a document to the database.

What I want to happen is that when there is a new entry to the Firebase database collection yyy under project xxx I want the Cloud Function funtion-1 to be triggered. Function-1 is the default (as per below) and a test worked fine.

I am using the main console and created a function named function-1. I can see the function itself in the firebase console:

https://console.firebase.google.com/u/0/project/xxx/functions/list

The collection I set is under project xxx, named yyy, and I can access it under

https://console.firebase.google.com/u/0/project/xxx/database/firestore/data~2Fyyy

I am in the functions console:

https://console.cloud.google.com/functions/edit/us-central1/function-1?project=xxx

and the setup is as follows:

Trigger: Firebase Realtime Database (Beta)
Event Type: Create
Database: xxx
Path: /data/yyy

Runtime is Python 3.7

Code is default Google Cloud Functions code:

def hello_rtdb(event, context):
    """Triggered by a change to a Firebase RTDB reference.
    Args:
         event (dict): Event payload.
         context (google.cloud.functions.Context): Metadata for the event.
    """
    resource_string = context.resource
    # print out the resource string that triggered the function
    print(f"Function triggered by change to: {resource_string}.")
    # now print out the entire event object
    print(str(event))

requirements.txt is empty

I have used other triggers (HTTP, or PubSub) successfully in other Google Cloud Functions but I cannot get the function to be triggered by a database event. I have tried a wide range of options for the path variable but couldn't make it work.

The options I tried for the path variable are:

/xxx/database/firestore/data/yyy
/database/firestore/data/yyy
/data/yyy
/yyy
yyy etc...

I am sure I am making a basic mistake but sadly the documentation isn't helping (probably because this is such a basic thing). How can I set this up in the right way?

Tommy Tommy · Accepted Answer · 2020-05-16T08:56:31

Are you using Google Firestore or Firebase Firestore? I know they are technically the same product under the covers but I believe they trigger different events. It may depend on whether you created the DB from Google Cloud Platform or Firebase.

$ gcloud functions event-types list

EVENT_PROVIDER                   EVENT_TYPE                                                EVENT_TYPE_DEFAULT  RESOURCE_TYPE       RESOURCE_OPTIONAL
google.firebase.database.ref     providers/google.firebase.database/eventTypes/ref.write   Yes                 firebase database   No
google.firestore.document        providers/cloud.firestore/eventTypes/document.write       Yes                 firestore document  No

I'm using event_provider=google.firestore.document and it works. Here's how I deploy Python functions onto Google Cloud. Assume main.py exists with your above code but function name is called hello_firestore.

$ gcloud functions deploy hello_firestore --entry-point hello_firestore --runtime python37 --trigger-event providers/cloud.firestore/eventTypes/document.write --trigger-resource "projects/$GCP_PROJECT/databases/(default)/documents/$DOC_PATH"

For Firebase Firestore, it should something like this but this is not tested because I created my Firestore from GCP rather than Firebase.

$ gcloud functions deploy hello_rtdb --entry-point hello_rtdb --runtime python37 --trigger-event providers/google.firebase.database/eventTypes/ref.write --trigger-resource "projects/_/instances/$GCP_PROJECT/refs/$DOC_PATH"

Another thing to watch for is that only Firestore native mode supports triggering of events as mentioned here in the section Limitations and guarantees.

Google cloud functions realtime database trigger setup in Python

1 Answers