Explanation:
The correct approach is to use inter-process signals (Option A) because preemptible VMs provide a 30-second window before shutdown. A shutdown script can send a signal (e.g., SIGTERM) to the application process, which can then handle it by disconnecting from the database gracefully. Options B and C are unsuitable as they involve user notifications or polling intervals longer than the shutdown window. Option D is unreliable because the application may not process the Pub/Sub message before termination. Signal handling (A) ensures immediate and direct notification to the application.
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You are developing an application that subscribes to a single Pub/Sub topic and inserts corresponding rows into a database. The application runs on Linux using preemptible VMs to minimize costs. How should you design a shutdown script to ensure a graceful shutdown?
A
Write a shutdown script that uses inter-process signals to notify the application process to disconnect from the database.
B
Write a shutdown script that broadcasts a message to all signed-in users that the Compute Engine instance is going down and instructs them to save current work and sign out.
C
Write a shutdown script that writes a file in a location that is being polled by the application once every five minutes. After the file is read, the application disconnects from the database.
D
Write a shutdown script that publishes a message to the Pub/Sub topic announcing that a shutdown is in progress. After the application reads the message, it disconnects from the database.