Graceful Shutdown for Python Applications

In production environments, applications often need to be restarted or updated. A graceful shutdown mechanism ensures that the application finishes its current tasks, releases resources, and exits cleanly without abruptly terminating, preventing data loss or corruption. This challenge focuses on implementing such a mechanism in a Python application.

Problem Description

Your task is to create a Python application that can perform a graceful shutdown. The application will simulate a long-running process (e.g., a web server or a background worker) that should respond to a shutdown signal by completing its current operations and then exiting.

Key Requirements:

Simulate a Long-Running Process: The application should include a loop or function that simulates ongoing work. This work should take a non-trivial amount of time to complete to allow for shutdown signals to be sent during its execution.
Signal Handling: The application must catch specific operating system signals (like SIGINT for Ctrl+C and SIGTERM for termination commands) to initiate the shutdown process.
Graceful Shutdown Logic: Upon receiving a shutdown signal, the application should:
- Stop accepting new tasks/requests (if applicable, though not explicitly required for this simulation).
- Allow currently executing tasks to finish.
- Cleanly release any acquired resources (e.g., close network connections, database connections, release locks).
- Exit the application with a specific exit code.
Non-Blocking Shutdown: The shutdown process itself should not block indefinitely if a task is taking too long. A timeout for completing the current tasks before forcing an exit might be considered for a more robust solution, but is not strictly required for the basic implementation.

Expected Behavior:

When the application is running, it should continue its simulated work.
When a shutdown signal is received, the application should print a message indicating it's shutting down.
It should then wait for any ongoing simulated work to complete.
Finally, it should print a message confirming shutdown and exit.

Edge Cases to Consider:

What happens if a shutdown signal is received multiple times?
What if the "work" being done is very short and finishes before the shutdown logic can fully engage?
How to handle potential race conditions between accepting new work and initiating shutdown.

Examples

Example 1:

Scenario: Running the application and pressing Ctrl+C.

Application Output during normal operation:
Processing item 1...
Processing item 2...
Processing item 3...

Upon pressing Ctrl+C:
[App logs current item processing message]
Received shutdown signal. Initiating graceful shutdown.
[App finishes processing item 3]
Finished processing item 3.
Releasing resources...
Shutdown complete. Exiting.

Program exit code: 0 (or a specific graceful exit code)

Example 2:

Scenario: Running the application and sending a SIGTERM signal.

Application Output during normal operation:
Working on task A for 5 seconds...
Working on task B for 7 seconds...

Upon receiving SIGTERM:
[App logs current task message]
Received shutdown signal. Initiating graceful shutdown.
[App waits for task B to finish after 7 seconds]
Finished task B.
Releasing resources...
Shutdown complete. Exiting.

Program exit code: 0 (or a specific graceful exit code)

Constraints

The simulated "work" should take between 1 to 10 seconds to complete per unit of work.
The application must handle signal.SIGINT and signal.SIGTERM.
The shutdown process should not involve indefinite waiting.
The solution must be implemented in Python 3.x.

Notes

The signal module in Python is your primary tool for handling OS signals.
Consider using a flag or event to signal to your main loop that a shutdown has been requested.
A simple time.sleep() can simulate work. For more complex scenarios, you might consider threading or asynchronous operations.
Think about how to stop new work from being started while allowing existing work to finish.
A common practice is to use sys.exit(0) for a successful graceful shutdown.

Graceful Shutdown for Python Applications

Problem Description

Key Requirements:

Simulate a Long-Running Process: The application should include a loop or function that simulates ongoing work. This work should take a non-trivial amount of time to complete to allow for shutdown signals to be sent during its execution.

Signal Handling: The application must catch specific operating system signals (like SIGINT for Ctrl+C and SIGTERM for termination commands) to initiate the shutdown process.

Graceful Shutdown Logic: Upon receiving a shutdown signal, the application should:

Stop accepting new tasks/requests (if applicable, though not explicitly required for this simulation).
Allow currently executing tasks to finish.
Cleanly release any acquired resources (e.g., close network connections, database connections, release locks).
Exit the application with a specific exit code.

Non-Blocking Shutdown: The shutdown process itself should not block indefinitely if a task is taking too long. A timeout for completing the current tasks before forcing an exit might be considered for a more robust solution, but is not strictly required for the basic implementation.

Expected Behavior:

When the application is running, it should continue its simulated work.

When a shutdown signal is received, the application should print a message indicating it's shutting down.

It should then wait for any ongoing simulated work to complete.

Finally, it should print a message confirming shutdown and exit.

Edge Cases to Consider:

What happens if a shutdown signal is received multiple times?

What if the "work" being done is very short and finishes before the shutdown logic can fully engage?

How to handle potential race conditions between accepting new work and initiating shutdown.

Examples

Example 1:

Scenario: Running the application and pressing Ctrl+C. Application Output during normal operation: Processing item 1... Processing item 2... Processing item 3... Upon pressing Ctrl+C: [App logs current item processing message] Received shutdown signal. Initiating graceful shutdown. [App finishes processing item 3] Finished processing item 3. Releasing resources... Shutdown complete. Exiting. Program exit code: 0 (or a specific graceful exit code)

Example 2:

Scenario: Running the application and sending a SIGTERM signal. Application Output during normal operation: Working on task A for 5 seconds... Working on task B for 7 seconds... Upon receiving SIGTERM: [App logs current task message] Received shutdown signal. Initiating graceful shutdown. [App waits for task B to finish after 7 seconds] Finished task B. Releasing resources... Shutdown complete. Exiting. Program exit code: 0 (or a specific graceful exit code)

Notes

The signal module in Python is your primary tool for handling OS signals.

Consider using a flag or event to signal to your main loop that a shutdown has been requested.

A simple time.sleep() can simulate work. For more complex scenarios, you might consider threading or asynchronous operations.

Think about how to stop new work from being started while allowing existing work to finish.

A common practice is to use sys.exit(0) for a successful graceful shutdown.