Скачать или смотреть How to Execute Python Code Only Once with Django on Gunicorn / Celery Restart?

Learn how to efficiently manage SFTP connections in Django applications using a singleton class to run Python code only once when Gunicorn/Celery services restart.
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This video is based on the question https://stackoverflow.com/q/63002867/ asked by the user 'Rohit Ranjan' ( https://stackoverflow.com/u/3980538/ ) and on the answer https://stackoverflow.com/a/63393118/ provided by the user 'Lalit Suthar' ( https://stackoverflow.com/u/10508834/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Managing SFTP Connections in Django with Singleton Pattern

When developing applications with Django, integrating tasks that depend on external resources, such as SFTP servers, can often lead to challenges, especially in instances requiring concurrent connections. One common issue is running into file descriptor errors due to too many open connections. If you're using Celery workers to download files from an SFTP server, you might be creating and closing connections frequently, which isn’t optimal.

The Problem

The typical workflow involves creating a new SFTP connection every time a Celery job is executed. However, if jobs run concurrently without proper handling of these connections, you can encounter issues like file descriptor errors. This occurs when there are too many connections hanging around, waiting for closure.

Now, what if you could set up a single SFTP connection that remains open while your application runs? This would not only save on resources but also help avoid these common pitfalls.

The Solution: Utilizing Singleton Pattern

The singleton design pattern is a powerful tool that allows a class to have only one instance and provides a global point of access to that instance. In the context of SFTP connections, you can create a Singleton class to manage this connection effectively, establishing it only once when your application starts.

Step 1: Implementing Singleton Class

Here’s how you can implement a singleton class in Python for your SFTP connections:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Creating the SFTP Singleton

Next, create a class for handling the SFTP connection using the singleton decorator we defined above:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Using the SFTP Singleton in Your Application

Now that you have created the SFTP singleton class, you can use it in your Django application as follows:

Connecting: Call the connect() method to establish the SFTP connection. This will only be done once.

Closing: Ensure to call close() when shutting down the application to clean up the resources properly.

Benefits of the Singleton Approach

Efficiency: Only one connection is maintained, reducing the load on the SFTP server and your application.

Resource Management: Helps avoid errors related to too many open file descriptors.

Simplicity: Simplifies connection management across multiple Celery tasks.

Conclusion

By implementing a singleton pattern for your SFTP connection in Django, you can efficiently manage resource usage and streamline your application's workflow. With this structured approach, you'll be able to avoid common pitfalls associated with multiple concurrent connections and improve the overall performance of your application.