This application synchronizes a GCS bucket to a local folder.

How it works

The application starts off by running gsutil cp to get all the contents of a GCS bucket.
The application then creates a Pub/Sub subscription attached to the provided topic (where notifications from GCS are sent to) and indefinitely listens to it for events while writing/deleting files based on the event type.

Prerequisites

1. Activate the Google Cloud Pub/Sub API, if you have not already done so. https://console.cloud.google.com/flows/enableapi?apiid=pubsub

2. Configure Pub/Sub notifications for Cloud Storage https://cloud.google.com/storage/docs/reporting-changes#rest-apis_1

Usage

The application is started by navigating to the app directory and running:

main.py --project GCLOUD_PROJECT_ID --pubsub_topic GCLOUD_PUBSUB_TOPIC_ID --source_bucket GCLOUD_BUCKET_NAME --source_bucket_path GCLOUD_BUCKET_PATH --destination_folder GCLOUD_DESTINATION_FOLDER

The input parameters may also be passed as environment variables as shown in the table below:

INPUT PARAMETER NAME	DESCRIPTION	REQUIRED?	DEFAULT VALUE
GCLOUD_PROJECT_ID	The ID of the GCP project that owns the subscription	Yes	None
GCLOUD_PUBSUB_TOPIC_ID	The ID of the Pub/Sub topic that receives notifications of changes to your GCS bucket	Yes	None
GCLOUD_BUCKET_NAME	The name of the GCS Bucket to sync data from	Yes	None
GCLOUD_BUCKET_PATH	The path to a specific folder in your GCS Bucket that you'd like to sync data from (Optional)	No	/
GCLOUD_DESTINATION_FOLDER	The absolute local path where the GCS bucket's contents will be stored (Optional)	No	/var/tmp/buckets/

A sample.env file is provided in the root folder to be used as a template for the environment variables.

Docker image

gcs-node-sync is publicly accessible as a Docker image:

gcr.io/cloudkite-public/gcs-node-sync:latest

Deleting the Pub/Sub subscription.

The Pub/Sub subscriptions created by this script are set to expire after 1 day of inactivity (subscriber activities include open connections, active pulls, or successful pushes).
The app/delete_pubsub_subscription.py is a small Python script which can be used to delete the Pub/Sub subscription created by the app/main.py script. It requires only two arguments which can be passed as environment variables:

INPUT PARAMETER NAME	DESCRIPTION
GCLOUD_PROJECT_ID	The ID of the GCP project that owns the subscription
GCLOUD_PUBSUB_TOPIC_ID	The ID of the Pub/Sub topic that receives notifications of changes to your GCS bucket

Usage: app/delete_pubsub_subscription.py --project GCLOUD_PROJECT_ID --pubsub_topic GCLOUD_PUBSUB_TOPIC_ID