Set Google Storage Bucket's default cache control

Question

Is there any way to set Bucket\'s default cache control (trying to override the public, max-age=3600 in bucket level every time creating a new object)

S

Answer 1

It is possible to write a Google Cloud Storage Trigger.

This function sets the Cache-Control metadata field for every new object in a bucket:

from google.cloud import storage

CACHE_CONTROL = "private"

def set_cache_control_private(data, context):
    """Background Cloud Function to be triggered by Cloud Storage.
       This function changes Cache-Control meta data.

    Args:
        data (dict): The Cloud Functions event payload.
        context (google.cloud.functions.Context): Metadata of triggering event.
    Returns:
        None; the output is written to Stackdriver Logging
    """

    print('Setting Cache-Control to {} for: gs://{}/{}'.format(
            CACHE_CONTROL, data['bucket'], data['name']))
    storage_client = storage.Client()
    bucket = storage_client.get_bucket(data['bucket'])
    blob = bucket.get_blob(data['name'])
    blob.cache_control = CACHE_CONTROL
    blob.patch()

You also need a requirements.txt file for the storage import in the same directory. Inside the requirements there is the google-cloud-storage package:

google-cloud-storage==1.10.0

You have to deploy the function to a specific bucket:

gcloud beta functions deploy set_cache_control_private \
    --runtime python37 \
    --trigger-resource gs:// \
    --trigger-event google.storage.object.finalize

For debugging purpose you can retrieve logs with gcloud command as well:

gcloud functions logs read --limit 50