This service will periodically, atomically sync a Google Cloud Storage directory to this container and server the contents over http.

Requirements for use:

• CONTROL_PORT env var - port that the control gRPC interface listens on. {DEFAULT: 9102}
• DATA_PORT env var - port that the files are served on {DEFAULT: 9103}
• GS_URL env var - gs:// url to the Google Cloud Storage directory where the files are downloaded from
• SYNC_DIR env var - absolute path to the directory in the container the files should be stored it; this should be a persistent volume and will need to have at least 2x the amount of space that the GCS directory uses
• SYNC_PERIOD env var - how often in seconds syncing should begin; if syncing is ongoing then the period just restarts
• GCP service account credentails mounted at /gcloud-credentials.json

This service can be signaled to wait before downloading by placing an empty file called WAIT in the top of the SYNC_DIR:

# Turn waiting on
gsutil cp /dev/null gs://path/to/sync_dir/WAIT

# Turn waiting off
gsutil rm gs://path/to/sync_dir/WAIT

The script tryit.py can be used to test the control interface. You can use curl to view the files. Here's a quick way to test the whole flow:

echo 'GS_URL=gs://your/gcs/directory/' > .env

pip install grpcio grpcio-tools

python -m grpc_tools.protoc -I . --python_out=. --grpc_python_out=. *.proto

docker-compose up --build -d

python tryit.py localhost:9102

curl http://localhost:9103/