Your app subscribes to a Pub/Sub topic and inserts rows into a database, running on Linux preemptible VMs. How should a shutdown script initiate a graceful shutdown?

The most effective way to initiate a graceful shutdown for an application on a Linux preemptible VM is by using inter-process signals. Signals like SIGTERM are standard mechanisms for telling a process to terminate gracefully, allowing it to clean up resources (like database connections) before exiting. This is a direct, efficient, and immediate method. Broadcasting messages to users is irrelevant to the application's internal shutdown process. Polling a file every five minutes is too slow and inefficient for a timely shutdown. Publishing a message to Pub/Sub and having the application read it introduces unnecessary latency and complexity, and doesn't guarantee the application will process it before being terminated, especially on a preemptible VM with a short shutdown notice.