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How can you debug Kubernetes deployments with multiple replicas?

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Kubernetes is a popular platform for managing containerized applications across multiple nodes. However, debugging Kubernetes deployments can be challenging, especially when they involve multiple replicas of the same pod. In this article, you will learn some useful tips and tools to help you troubleshoot your Kubernetes deployments with multiple replicas.

本文章的要点总结

Use kubectl debug:

This command launches a temporary container in your existing pod, allowing you to inspect and troubleshoot without disrupting the original state. It's like having a spyglass into your pod's soul.
Leverage health checks:

Regularly implementing liveness and readiness probes ensures your pods are healthy and ready for traffic. Think of it as giving your deployments a routine check-up to maintain peak performance.

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Cuong Nguyen Duc

SRE | DevOps | Cloud Engineer
Abimbola Okusada

Netcool | DevOps | Automation |…

1 Check the pod status

The first step to debug your Kubernetes deployments is to check the status of your pods. You can use the kubectl get pods command to list all the pods in your current namespace, or add the -n flag to specify a different namespace. You can also use the -l flag to filter the pods by labels. The output will show you the name, ready state, restart count, and status of each pod. You can look for pods that are in an error, crash loop, or pending state, and investigate the root cause.

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Abimbola Okusada

Netcool | DevOps | Automation | Terraform| Linux | GitOps |SRE | AIOP| AWS| Docker| Kubernetes|CI/CD|
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Health Checks: Implement and check liveness and readiness probes for your pods. These probes can help Kubernetes determine whether a pod is healthy and ready to receive traffic.

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Cuong Nguyen Duc

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kubectl describe command- Useful for checking the events and status of a pod. It works on both individual pods and across all pods in a deployment.

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2 View the pod logs

The next step to debug your Kubernetes deployments is to view the logs of your pods. You can use the kubectl logs command to print the standard output and standard error of your pod containers. You can specify the pod name, the container name (if there are multiple containers in a pod), and the namespace (if different from the current one). You can also use the -f flag to follow the logs in real time, or the --tail flag to limit the number of lines to display. The logs can help you identify any errors, exceptions, or warnings in your application code or configuration.

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3 Exec into the pod

Another step to debug your Kubernetes deployments is to exec into the pod and run commands inside the container. You can use the kubectl exec command to execute a command in a specific container of a pod. You can specify the pod name, the container name (if there are multiple containers in a pod), and the namespace (if different from the current one). You can also use the -it flag to open an interactive shell session. This can help you inspect the environment variables, files, processes, network, and dependencies of your container.

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Cuong Nguyen Duc

SRE | DevOps | Cloud Engineer
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To examine the environment variables of a pod in Kubernetes, you can use the kubectl exec command to create an interactive shell session on the specific pod. Once you are inside the pod, you can use shell commands, like printenv or env, to print the environment variables.

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4 Use port forwarding

Sometimes, you may want to debug your Kubernetes deployments by accessing your pod services from your local machine. You can use the kubectl port-forward command to forward one or more local ports to a pod. You can specify the pod name, the local port, and the pod port, and optionally the namespace (if different from the current one). You can then use your browser or curl to access your pod service at localhost:local_port. This can help you test your pod functionality, performance, and security.

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5 Apply probes

One more step to debug your Kubernetes deployments is to apply probes to your pod containers. Probes are periodic checks that Kubernetes performs to monitor the health and readiness of your containers. You can define two types of probes: liveness probes and readiness probes. Liveness probes check if your container is still running, and restart it if it fails. Readiness probes check if your container is ready to serve requests, and remove it from the service load balancer if it fails. You can configure your probes to use HTTP, TCP, or exec methods, and specify the initial delay, interval, timeout, success threshold, and failure threshold. Probes can help you avoid sending traffic to unhealthy or unready pods, and improve the reliability and availability of your deployments.

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6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

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Cuong Nguyen Duc

SRE | DevOps | Cloud Engineer
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Using kubectl debug command allows you to create debug containers which come handy in troubleshooting scenarios. You can run a temporary container in a running Pod for debugging, which can provide important insights into the running state of existing containers. kubectl debug -it my-app-5d5f6b69b-nqhml --image=busybox --target=my-app This command will create an ephemeral debug container named debugger-my-app-5d5f6b69b-nqhml running busybox in the existing pod my-app-5d5f6b69b-nqhml targeting the existing container my-app for debugging.

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How can you debug Kubernetes deployments with multiple replicas?

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1 Check the pod status

2 View the pod logs

3 Exec into the pod

4 Use port forwarding

5 Apply probes

6 Here’s what else to consider

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