Bottle and Gunicorn not stopping after a request in Python

What will you learn?

Explore how to effectively address the issue of Bottle/Gunicorn servers not responding to SIGTERM signals after processing requests.

Introduction to the Problem and Solution

In Python, when utilizing Bottle with Gunicorn, encountering situations where the server fails to stop gracefully post receiving a SIGTERM signal following a request is not uncommon. This can result in hanging processes or unresponsive servers. To tackle this issue, adjustments are necessary either in the code or configuration settings.

One prevalent solution involves explicitly managing the shutdown process within the application code by capturing the SIGTERM signal and ensuring all pending requests are completed before shutting down the server appropriately.

Code

import signal

def graceful_shutdown(signum, frame):
    print("Shutting down server gracefully...")
    # Add cleanup tasks here before shutting down
    exit(0)

signal.signal(signal.SIGTERM, graceful_shutdown)

# Copyright PHD

Note: Customization may be required based on individual application requirements.

Explanation

In the provided code snippet: – The signal module is imported for handling signals. – A function graceful_shutdown is defined to execute upon receiving a SIGTERM signal. – Within this function, any essential cleanup tasks can be included before exiting. – Utilizing signal.signal() associates the SIGTERM signal with our custom shutdown handler.

By implementing this approach, proper response to termination signals ensures correct cleanup actions before server shutdown in Bottle/Gunicorn applications.

How do I test if my implementation for handling SIGTERM works?

You can manually send a SIGTERM signal using tools like the kill command on Unix-based systems or Task Manager on Windows.

Are there other ways to handle graceful shutdowns in Python applications?

Yes, frameworks like Flask offer built-in methods such as the before_first_request decorator for executing functions prior to handling any requests.

Can I use different signals apart from SIGTERM for shutdown handling?

Certainly! Various POSIX signals like SIGHUP or custom signals within your application logic can be managed.

What happens if I don’t handle shutdown properly?

Improper shutdowns may result in resource leaks, incomplete transactions, or data corruption due to abrupt terminations without proper cleanup steps.

Should I only apply this technique for web applications using Bottle/Gunicorn?

No, it’s advisable for any long-running Python process where clean termination is crucial.

How do I know if my server terminated gracefully in production environments?

Logging relevant messages or metrics during shutdown procedures enables monitoring for successful graceful exits.

Is there an alternative way without modifying code directly?

Certain deployment platforms offer settings or environment variables tailored for managing shutdown behavior without direct alterations to application logic.

Conclusion

Ensuring servers shut down gracefully is paramount for stability and reliability in production environments. By addressing how Bottle/Gunicorn respond to termination signals like SIGTERM accurately, operational smoothness during server stops is guaranteed. For additional assistance or related queries visit PythonHelpDesk.com.