Resolving Python Script Logging Issues While Using SSH in Kubernetes

Learn how to troubleshoot and fix logging problems in your Python scripts when running them over SSH, especially with Kubernetes.
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This video is based on the question https://stackoverflow.com/q/76841948/ asked by the user 'Deekly' ( https://stackoverflow.com/u/21176994/ ) and on the answer https://stackoverflow.com/a/76844233/ provided by the user 'Kenster' ( https://stackoverflow.com/u/13317/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Resolving Python Script Logging Issues While Using SSH in Kubernetes

When working with Python scripts that manage Kubernetes pods, you may encounter a frustrating problem: the script runs correctly when executed locally on the Kubernetes master, but fails to log output properly when invoked remotely via SSH. If you're finding yourself in similar shoes, you're not alone! Let’s explore this issue and dive into an effective solution.

The Problem

You have developed a script (kube_reload.py) that checks the status of Kubernetes pods and, under certain circumstances, writes their logs and deletes them. The script operates perfectly when executed directly on the Kubernetes master. However, when you connect to that server via SSH from another server and run the same command, the pods get deleted without the logs being written, and no errors are thrown.

This can lead to confusion, especially when you have implemented all permissions correctly (777 for scripts and directories) and can run the script manually with all expected outputs.

Understanding the Cause

The root of the problem lies in how the current working directory is set when running the script via SSH. Here’s a breakdown of what's happening:

Local Execution: When you run ./kube_reload.py rap rock directly on the Kubernetes master, the working directory is set to the directory where your script resides (e.g., deekly). Therefore, it writes the log files (like rap.log and rock.log) in the same location.

Remote Execution via SSH: The command used to execute the script through SSH (sp.Popen(f'ssh developer@ radio1 python3 ~/deekly/kube_reload.py {stream}', shell=True)) sets the working directory to the developer's home directory, not the deekly directory. As a result, the logs get redirected to the home directory, often leading to confusion about where they are actually stored.

Solutions

To resolve this logging issue, you have three main options:

1. Modify the Script for Custom Log Directory

You can modify the kube_reload.py script to specify exactly where the log files should be saved rather than relying on the current working directory. For example:

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

2. Change Working Directory in the Script

Another approach is to change the working directory within your script before trying to open the log files. You can do this using os.chdir:

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

3. Adjust the SSH Command

Finally, you can modify the SSH command used to invoke kube_reload.py to ensure it executes in the correct directory. Here’s how to do that:

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

Be sure to properly escape any quotes in your Python code as needed!

Conclusion

Debugging logging issues when running scripts over SSH can be quite challenging, especially in the context of Kubernetes. By understanding the flow and where your logs are being directed, you can easily address and refine your scripts for a seamless operational experience.

No matter which solution you choose, always ensure to test your configuration thoroughly to confirm that logs are being written as expected.

Have you encountered similar issues while working with Python and Kubernetes? Share your thoughts and experiences in the comments below!

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