app.py

from flask import Flask, request
import os
app = Flask(__name__)


@app.route("/", methods=["POST"])
def index():
    envelope = request.get_json()
    if not envelope:
        msg = "no Pub/Sub message received"
        print(f"error: {msg}")
        return f"Bad Request: {msg}", 400

    if not isinstance(envelope, dict) or "message" not in envelope:
        msg = "invalid Pub/Sub message format"
        print(f"error: {msg}")
        return f"Bad Request: {msg}", 400

    pubsub_message = envelope["message"]

    name = "World"
    if isinstance(pubsub_message, dict) and "data" in pubsub_message:
        name = base64.b64decode(pubsub_message["data"]).decode("utf-8").strip()

    print(f"Hello {name}!")


if __name__ == "__main__":
    # This is used when running locally, Gunicorn is used to run the application on Cloud Run
    app.run(debug=True, host="0.0.0.0", port=8080)