Скачать или смотреть Resolving Container Crashing in Kubernetes Due to SIGQUIT Signal

Discover how to fix your Kubernetes container that keeps crashing with a `SIGQUIT` signal caused by a misconfigured liveness probe. Learn step-by-step solutions and essential tweaks for your NGINX setup.th
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This video is based on the question https://stackoverflow.com/q/69924187/ asked by the user 'Casey Flynn' ( https://stackoverflow.com/u/480807/ ) and on the answer https://stackoverflow.com/a/69924266/ provided by the user 'akop' ( https://stackoverflow.com/u/6537157/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding Container Crashes in Kubernetes

If you’re running a Kubernetes (k8s) cluster and have been grappling with a container that continuously crashes without a clear reason, you’re not alone. Many developers encounter similar issues, especially when it comes to improperly configured health checks.

This post aims to shed light on one such issue, particularly involving an NGINX server container that keeps receiving a SIGQUIT signal, leading to constant crashes. Let's explore the root cause, the solution, and how to ensure your container runs smoothly.

The Problem: Container Crashing on SIGQUIT

In the reported scenario, an NGINX server container is crashing, as evidenced by logs showing the receipt of a SIGQUIT signal:

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This signal is often a clear indicator that something is wrong. Specifically, Kubernetes is trying to check the health of the application in the container, but it is unable to confirm that the container is alive, leading to premature termination.

The Solution: Adjusting the Liveness Probe

Luckily, this issue may stem from a simple configuration oversight in the liveness probe setting. The liveness probe is critical for Kubernetes to determine when to restart an unhealthy container. In this case:

Key Configuration

Current Configuration: The liveness probe is configured with an HTTPS scheme on port 80.

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Recommended Change

Modification: Change the probe to use HTTP instead of HTTPS. This can be done by editing the Kubernetes pod specification or deployment configuration, specifically at:

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Why This Works

Using HTTPS incorrectly on port 80 confuses Kubernetes as it attempts to probe the application. When the probe fails (due to receiving a TLS handshake that it cannot decrypt), Kubernetes marks the pod as unhealthy. Per Kubernetes' policy, it then sends signals like SIGQUIT for graceful shutdown. This can trigger a loop of crashes as Kubernetes tries to restart the unhealthy container but finds the same issue.

Verifying the Fix

Once you've made this change, monitor your container logs:

Look out for repetitive entries indicating the health probe status.

Any 400-series errors will point towards misconfiguration in how the probe is set. Your goal is to see successful probes without errors.

Additional Logs Insight

By reviewing logs around the time of the crash:

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

These logs show that Kubernetes is trying to connect using TLS (due to its previous configuration), and failing to get a readable response, leading to the shutdown.

Conclusion

Adjusting the liveness probe, specifically changing from HTTPS to HTTP on port 80, is often a simple yet effective solution to resolve crashing issues related to SIGQUIT signals in Kubernetes. By ensuring your applications are correctly configured, you can maintain service availability and prevent frustrating crash loops.

For further assistance, feel free to share your experiences or consult the community for additional troubleshooting steps!