Set default settings to 'no-cache' on Google Cloud Storage - google-app-engine

Question

Is there a way to set all public links to have 'no-cache' in Google Cloud Storage?
I've seen solutions to use gsutil to set the "Cache-Control" upon file-upload, but I'm looking for a more permanent solution.
There was a conversation about providing a cache invalidation feature but I didn't quite follow the reasoning. Any explanations would be greatly appreciated!
it would be difficult to provide a cache invalidation feature because once served with a non-0 cache TTL any cache on the Internet (not just those under Google's control) is allowed (per HTTP spec) to cache the data
Thanks!

Answer 1

For a more permanent one-time-effort solution, with the current offerings on GCP, you can do this with Cloud Functions.
Create a new Funciton, set the Event type to "On (finalizing/creating) file in the selected bucket" - google.storage.object.finalize. Make sure to select the bucket you want this on. In the body of the function, set the cacheControl / Cache-Control attribute for the blob. The attribute name depends on the language. Here's my version in Python, using cache_control:
main.py:
match the function name below to the Entry point
from google.cloud import storage
def set_file_uncached(event, context):
file = event # auto-generated
print(f"Processing file: {file=}") # logging, if you want it
storage_client = storage.Client()
# we expect just one with that name
blob = storage_client.bucket(file["bucket"]).get_blob(file["name"])
if not blob:
# in case the blob is deleted before this executes
print(f"blob not found")
return None
blob.cache_control = "public, max-age=0" # or whatever you need
blob.patch()
requirements.txt
google-cloud-storage
From the logs: Function execution took 1712 ms, finished with status: 'ok'. This could have been faster but I've set the minimum to 0 instances so it needs to spin-up for each upload. Depending on your usage and cost constraints, you can set it to 1 or something higher.
Other settings:
Retry on failure: No/False
Region: [wherever your bucket is]
Memory allocated: 128 MB (smallest available currently)
Timeout: 5 seconds (smallest available currently, function shouldn't take longer)
Minimum instances: 0
Maximum instances: 1