Best Practices for Modifying Running Pods in Kubernetes: Deployment vs. Pod

Описание: Learn the recommended approach for modifying running pods in Kubernetes. Understand the critical difference between editing a `Deployment` and a `Pod` and why choosing the right method is essential for maintaining desired configurations.
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This video is based on the question https://stackoverflow.com/q/68195956/ asked by the user 'Vowneee' ( https://stackoverflow.com/u/16092023/ ) and on the answer https://stackoverflow.com/a/68197146/ provided by the user 'Emruz Hossain' ( https://stackoverflow.com/u/7695859/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Challenge: Modifying Running Pods in Kubernetes

In Kubernetes, developers often face the need to modify the configuration of running pods. This can stem from adjustments in application settings, environment variables, or resource requirements. However, the question arises: should one modify the Deployment or the Pod directly? This post aims to clarify the best practice for modifying pod configurations and explain why it's vital to stick to a particular approach.

The Recommended Approach: Modify the Deployment

When it comes to making changes to running pods, the clear recommendation is to modify the Deployment, not the Pod. Here’s why this approach is essential:

1. Understanding the Role of a Deployment

Desired State Management: A Deployment serves as a blueprint for your pods. It defines the desired state of the application and its container specifications.

Continuous Monitoring: Kubernetes utilizes a Deployment controller that continuously monitors its associated pods. This controller ensures that the actual state of the pods aligns with the desired state specified in the Deployment.

2. Consequences of Modifying Pods Directly

Overwriting Changes: If you were to edit an individual Pod's configuration using commands such as kubectl edit pod, you may find that your changes are temporary. The Deployment controller actively monitors the Deployment specifications and will overwrite any changes made to the Pods during its next reconciliation cycle.

Lack of Consistency: Direct modifications to Pods can lead to inconsistencies within the cluster, where the managed pods diverge from the intended setup outlined by the Deployment.

3. Steps to Modify the Deployment

To safely and efficiently modify running pods, follow these steps:

Edit the Deployment: Use the command kubectl edit deploy [DEPLOYMENT_NAME]. This opens the deployment specification in your default editor.

Make your changes: Adjust the necessary properties, such as environment variables or resource limits.

Save your changes: Once your modifications are complete, saving will trigger an update process.

Monitor the Update: Use kubectl rollout status deploy [DEPLOYMENT_NAME] to ensure that the update completes successfully and your desired state is achieved.

4. Example of Modifying a Deployment

Here’s a quick example showing how to modify an environment variable in a Deployment:

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In your editor, locate the container specification and modify the environment variable as required:

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Once saved, Kubernetes will automatically handle the recreation of pods with the new configurations based on the updated Deployment.

Conclusion: The Importance of Modifying the Deployment

In essence, always prefer modifying the Deployment rather than making changes directly to the Pods in Kubernetes. This practice helps maintain the desired state of the application and preserves system integrity. By following this guidance, you ensure consistent configurations and avoid unintended overwrites by the Deployment controller.

For more insights on Kubernetes best practices, stay tuned to our blog!