How to write a Cloud Function to listen and respond events such as when a file is created, changed, or removed?

Question

In GCP, I am having trouble finding an example on how to listen and respond to Cloud Storage events such as when a file is created, changed, or removed.

I tried looking at the GCP docs on how to do this, but there is nothing there. I am looking for a simple Python example using Cloud Functions to listen and respond to when a file is created, changed, or removed in my GCS Bucket.

Answer 1

You can trigger a Cloud Function V2 on a Cloud Storage event :

gcloud functions deploy YOUR_FUNCTION_NAME \
--gen2 \
--trigger-event-filters="type=EVENT_TYPE" \
--trigger-event-filters="bucket=YOUR_STORAGE_BUCKET" \
...

• YOUR_FUNCTION_NAME is the Cloud Function name
• EVENT_TYPE is the GCS file event (Object finalized, Object deleted
  ...). Check the link above on the doc for the different event types
• YOUR_STORAGE_BUCKET is the GCS bucket concerned by the event

For the code of the Cloud Function, you check this link :

import functions_framework

# Register a CloudEvent function with the Functions Framework
@functions_framework.cloud_event
def my_cloudevent_function(cloud_event):
  # Your code here
  # Access the CloudEvent data payload via cloud_event.data