Kubernetes: Deprecated APIs

Small world. Big idea!

API deprecation - what is that?

As Kubernetes feature set evolves, APIs have to evolve too in order to support this change. There are rules in place that aim to guarantee compatibility and stability, and also it does not happen with every release, but eventually, you will have to use the new API version and format as the old one won’t be supported anymore.

Why is this important with the 1.16 release?

A few deprecated APIs have been kept around in the last couple of K8s versions and finally getting completely removed in Kubernetes 1.16 release. Namely following API Groups and versions:

If you try to create a resource using one of these with 1.16, the operation will simply fail.

How to check if I am affected?

You can manually go through all your manifests, but that can be fairly time-consuming, it’s easy to miss some and might be highly unpractical if you have multiple teams deploying to the cluster, or simply don’t have all the current manifest at one place. And this is where Kube-No-Trouble aka kubent comes to help.

Sounds good, how do I use it?

The simplest way is to install is:

sh -c "$(curl -sSL 'https://git.io/install-kubent')"

or Homebrew

kubent is available as a formula on Homebrew. If you’re using macOS or Linux, you can run the following command to install kubent:

brew install kubent

This will install the latest version of kubent.

 π ~> which kubent
/opt/homebrew/bin/kubent

Configure kubectl’s current context to point to the cluster you want to check and run the kubent tool:

 π ~> kubent
6:25PM INF >>> Kube No Trouble `kubent` <<<
6:25PM INF Initializing collectors and retrieving data
6:25PM INF Retrieved 103 resources from collector name=Cluster
6:25PM INF Retrieved 0 resources from collector name="Helm v3"
6:25PM INF Loaded ruleset name=deprecated-1-16.rego
6:25PM INF Loaded ruleset name=deprecated-1-20.rego
__________________________________________________________________________________________
>>> 1.16 Deprecated APIs <<<
------------------------------------------------------------------------------------------
KIND         NAMESPACE     NAME                    API_VERSION
Deployment   default       nginx-deployment-old    apps/v1beta1
Deployment   kube-system   event-exporter-v0.2.5   apps/v1beta1
Deployment   kube-system   k8s-snapshots           extensions/v1beta1
Deployment   kube-system   kube-dns                extensions/v1beta1
__________________________________________________________________________________________
>>> 1.20 Deprecated APIs <<<
------------------------------------------------------------------------------------------
KIND      NAMESPACE   NAME           API_VERSION
Ingress   default     test-ingress   extensions/v1beta1

Kubent will connect to your cluster, retrieve all resources that might be affected, scan, and print summary of those that are.

You can also use -f json flag to get output in JSON format which is more suitable in case you want to integrate this in your CI/CD pipeline or process the results further. More details on available configuration options are described in the README of kube-no-trouble repo.

Summary

So hopefully this will help you to detect and deal with the use of deprecated APIs in your Kubernetes clusters before these could cause you any trouble.

It is still very early for the kubent tool and I would love to hear any comments, suggestions, and if you find it useful. Safe sailing!

©-Duy Henry. All images copyrighted.