Kubectl Rollout Restart: What Is It and How to Use It?

The main function of Kubernetes is to manage and deploy your application run successfully. And Kubectl Rollout restart is one of the useful commands that allows you to restart deployments, which can help resolve various issues related to application failures, configuration changes, or software updates. In this blog, we will dive deep into what the kubectl rollout restart command is, why it’s used, and how to use it effectively in real-world scenarios.

What is Kubectl Rollout Restart?

In Kubernetes, kubectl rollout restart is a command used to start a new rollout process for three specific Kubernetes objects: Deployment, DaemonSet, and StatefulSet. A rollout process means a gradual, step-by-step recreation of pods. The old pods are not removed entirely until the new pods are running successfully. This process ensures that your application remains available throughout the restart process.

One of the key advantages of the Kubectl rollout restart command is that it enables you to recreate the pods associated with the aforementioned objects, regardless of whether their configuration has been modified or not.

How to use Kubectl Rollout Restart?

While the Kubectl rollout restart is simple to use, there are best practices and considerations for using it effectively in a Kubernetes environment. As:

1. Monitor the restart process: After initiating a rollout restart, it’s important to monitor the progress of the restart. You can use the following command to check the status:

Kubectl rollout status deployment <deployment-name>

This ensures that you can see the progress of the restart and confirm when it’s completed successfully. If there are any issues with the rollout, this command will provide insights into which pod or part of the deployment is experiencing problems.

2. Use in conjunction with health probes: Health probes (liveness and readiness probes) are essential to ensure that Kubernetes only routes traffic to healthy pods. When using Kubectl rollout restart, ensure that your deployment is configured with proper health probes:

Liveness Probe: Ensures that the pod is still alive and running.
Readiness Probe: Ensures that the pod is ready to accept traffic.

These probes prevent Kubernetes from sending traffic to a newly restarted pod before it’s ready.

Here’s an example of adding a readiness probe to a deployment:

readinessProbe:
httpGet:
path: /health
port: 80
initialDelaySeconds: 5
periodSeconds: 10

3. Avoid Frequent Rollout Restarts: While restarting a deployment can resolve certain issues, frequent restarts may indicate deeper problems with your application or cluster configuration. If you find yourself regularly using Kubectl rollout restart, consider investigating the root cause of the recurring issues.

Frequent restarts can also lead to instability and degraded performance, so it’s important to address underlying problems rather than relying on rollouts as a long-term solution.

4. Use in Staging Before Production: If you’re making significant changes to your application or configuration, always test the restart process in a staging environment before using it in production. This ensures that any potential issues are caught early, preventing downtime or service disruptions in production.

5. Automate the process with CI/CD: In a DevOps workflow, it’s common to automate deployment and restart processes using CI/CD pipelines. You can integrate kubectl rollout restart into your CI/CD pipeline to automatically restart deployments when needed, for example, after a configuration change or software update.

Here’s a basic example of how this might look in a CI/CD pipeline:

kubectl apply -f deployment.yaml
kubectl rollout restart deployment my-app-deployment
kubectl rollout status deployment my-app-deployment

This automates the process of applying deployment changes and ensuring a restart occurs when necessary.

6. Scale deployments before restarting: If your deployment handles high traffic, consider scaling the deployment before restarting it to avoid disruptions during the restart process. You can temporarily increase the number of replicas before issuing the restart command and scale back after the restart is complete.

kubectl scale deployment my-app-deployment --replicas=5
kubectl rollout restart deployment my-app-deployment
kubectl scale deployment my-app-deployment --replicas=3

This strategy ensures there are extra pods available to handle traffic while the restart is in progress.

Benefits of Using Kubectl Rollout Restart

The kubectl rollout restart command provides several advantages over manual pod deletion or scaling operations:

Zero Downtime: Since Kubernetes follows the rolling update strategy during a restart, there is minimal to no downtime. The application remains available throughout the process.
Safe Restarting: The command ensures that pods are restarted in a controlled manner, respecting the deployment’s rollout strategy. This prevents service disruption, which can occur with manual restarts or deletions.
Minimal Effort: Restarting a deployment with kubectl rollout restart doesn’t require modifying the deployment's configuration or creating a new deployment. It's a quick and straightforward way to refresh the pods.
Environment and Secret Refresh: If environment variables, config maps, or secrets are updated, the command ensures the pods pick up the new values without requiring any changes to the deployment configuration.

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Conclusion

The Kubectl rollout restart command is an important tool in Kubernetes to restart deployments without downtime. It’s particularly useful for refreshing environment variables, updating image caches, and recovering from unhealthy pods. Follow the steps mentioned in the blog to ensure your deployments stay updated and running smoothly in a Kubernetes cluster. Its simplicity and reliability make it a go-to solution for maintaining application stability with minimal effort. Regular use of this command can help you avoid disruptions and ensure high availability in your Kubernetes environment.

For more information and any kind of assistance related to Kubernetes, connect with SupportFly.