Hey everyone! I'm relatively new to managing Kubernetes clusters, primarily having been a user until now. Currently, I'm running a local K8s cluster set up with two nodes - one control plane and one worker. I've built and deployed a full application manually without using Helm. The backend is a Python Flask app, and I've also tried using Node.js for it. For the frontend, I'm serving a static HTML and JS application through Nginx. Everything seems to be set up correctly, with the backend configured as a `ClusterIP` service and the frontend as a `NodePort`.
Here's the issue I'm facing: the backend pod starts out as `Running`, but then it transitions to `Completed`, and eventually, I see a state of `CrashLoopBackOff`. When I check the logs for the backend pod, it shows nothing at all. Interestingly, the Flask app functions perfectly when I run it using Podman on the worker node, handling requests and actions as expected. Meanwhile, the frontend pod does have several restarts but finally lands in a running state after a few minutes. However, the frontend can't communicate with the backend because it's not up and running.
I've done some diagnostics, including verifying that the backend image runs fine using `podman run -p 5000:5000 backend:local`. When I describe the backend pod, I see that it shows `Last State: Completed` with an `Exit Code: 0`, but there's no crash trace available. I've checked the YAML configuration and nothing stands out as off—just a single container, correct port exposure, and no health checks described. The logs are also empty for the backend, with no output to suggest what's causing the shutdown.
In more detail, I suspect that the pod exits cleanly after it handles the requests, and that's why it ends too soon, causing Kubernetes to think that it has crashed. This is reflected in the output from running `kubectl get pods`, where I see the backend in a `CrashLoopBackOff` state.
I'm curious: why does this pod finish its execution without keeping the service alive? And, why does it run flawlessly on Podman but fails in Kubernetes? I'm open to any suggestions on files or configurations you might want to see to help troubleshoot this issue!
1 Answer
Have you tried checking the previous logs for the failing pod? You can do that by running `kubectl logs --previous`. If your pod exits with an exit code of 0, that usually means your app is exiting cleanly, so you may need to adjust your app's logic to ensure it keeps running and doesn't terminate too early.
Thanks! I’ll check those logs. But is there any chance that it's just a misconfiguration in my code, like trying to run two servers on the same port?