Concepts

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Configuration Best Practices

This document highlights and consolidates configuration best practices that are introduced throughout the user guide, Getting Started documentation, and examples.

This is a living document. If you think of something that is not on this list but might be useful to others, please don’t hesitate to file an issue or submit a PR.

General Configuration Tips

“Naked” Pods vs ReplicaSets, Deployments, and Jobs

A Deployment, which both creates a ReplicaSet to ensure that the desired number of Pods is always available, and specifies a strategy to replace Pods (such as RollingUpdate), is almost always preferable to creating Pods directly, except for some explicit restartPolicy: Never scenarios. A Job may also be appropriate.

Services

  FOO_SERVICE_HOST=<the host the Service is running on>
  FOO_SERVICE_PORT=<the port the Service is running on>

This does imply an ordering requirement - any Service that a Pod wants to access must be created before the Pod itself, or else the environment variables will not be populated. DNS does not have this restriction.

If you only need access to the port for debugging purposes, you can use the apiserver proxy or kubectl port-forward.

If you explicitly need to expose a Pod’s port on the node, consider using a NodePort Service before resorting to hostPort.

Using Labels

A Service can be made to span multiple Deployments by omitting release-specific labels from its selector. Deployments make it easy to update a running service without downtime.

A desired state of an object is described by a Deployment, and if changes to that spec are applied, the deployment controller changes the actual state to the desired state at a controlled rate.

Container Images

The imagePullPolicy and the tag of the image affect when the kubelet attempts to pull the specified image.

Note: To make sure the container always uses the same version of the image, you can specify its digest, for example sha256:45b23dee08af5e43a7fea6c4cf9c25ccf269ee113168c19722f87876677c5cb2. The digest uniquely identifies a specific version of the image, so it is never updated by Kubernetes unless you change the digest value.
Note: You should avoid using the :latest tag when deploying containers in production as it is harder to track which version of the image is running and more difficult to roll back properly.
Note: The caching semantics of the underlying image provider make even imagePullPolicy: Always efficient. With Docker, for example, if the image already exists, the pull attempt is fast because all image layers are cached and no image download is needed.

Using kubectl

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