gk8s: A Shell repository from icy

Description

Scripting-friendly tool to work with multiple k8s clusters, with ability to provide a concise way to write system documentation, to avoid human mistake and finally, to improve team communication and work.

Ideas

The known way

$ export KUBECONFIG=~/.kube/config:~/.kube/kubconfig2
$ kubectl config use-context my-context
$ kubectl get nodes
$ kubectl --context=foo get nodes
$ helm --kube-context=foo list
$ custom-command --custom-option-to-fetch-kubeconfig-and-context

This new way

$ gk8s :my-cluster get nodes
$ gk8s :my-cluster helm list
$ gk8s :my-cluster -- helm list
$ gk8s :my-cluster -- custom-command   # KUBECONFIG will be set accordingly with default context!

The tool doesn't accept delete action by default. You must touch a local file .delete or using environment setting DELETE=true to activate the deletion:

$ gk8s :my-cluster delete pod foo
:: Error: File .delete doesn't exist in the current directory.

$ touch .delete; gk8s :my-cluster delete pod foo
Error from server (NotFound): pods "foo" not found

$ DELETE=true gk8s :my-cluster delete pod foo
Error from server (NotFound): pods "foo" not found

Touching file .delete doesn't support multiple actions in parallel.

Why

Improve communication
Easy to write examples in documentation
Design for scripting purpose with better error handling
Slow down dangerous commands by default
Have fun with Golang
Somebody hates shell scripting :D
Just don't have everything in ~/.kube/config
Easily trace important command from history

Seriously, why don't just use `kubectl config`

$ kubectl config set-cluster foo can return happily (aka, without any error)
$ kubectl config set-context foo can return happily (aka, without any error)
$ kubectl foo --context=foo is great but if you don't use kubectl you need to remember another option e.g. kube-context (Helm)
export KUBECONFIG is long, error-prone

You may shoot yourself in the foot with shared kubectl configuration files. And having multiple clusters, contexts in the same ~/.kubectl/[config] is not easy.

And your friend or team mate hardly replicates your command on their laptop because they may have wrong/invalid/different KUBECONFIG.

Using external configuration gives you neutral knowledge about your history. For example

$ history | grep kubectl
kubectl get pods ...
kubectl edit deployment ...

You get no idea of the cluster on which you executed the command(s).

Updated on July 2021: This topic is also discussed on HN: https://news.ycombinator.com/item?id=27739134

Getting started

Starting from v1.1.1, you can download binary files generated automatically by Github-Action (via goreleaser tool). You find the files from the release listing page: https://github.com/icy/gk8s/releases

To install on your laptop by local compiling process, please try the popular way

$ go get -u github.com/icy/gk8s
$ export PATH=$PATH:"$(go env GOPATH)/bin"

Now prepare your configuration. It's important to note that we don't like to put multiple cluster configurations in the same file. That's possible, but this tool highly recommends to have seperated files for each cluster:

$ mkdir -pv ~/.config/gk8s/
$ cp -fv /path/to/cluster-config ~/.config/gk8s/my-cluster

Repeat the last steps for any other cluster.

If you are using EKS, you use a script generator too:

$ aws eks update-kubeconfig \
  --profile some_profile_name \
  --name cluster_name \
  --alias cluster_alias \
  --region eu-west-1 \
  --dry-run
  >  ~/.config/gk8s/cluster_name

Examples

The following commands yield the same result:

$ gk8s :cluster get nodes
$ gk8s :cluster kubectl get nodes
$ gk8s :cluster -- kubectl get nodes

Both kubectl and helm don't need any separator (--). The following commands are the same:

$ gk8s :cluster helm list
$ gk8s :cluster -- helm list

Some notes

The command kubectl is used by default.
When you specify --, the remained part of arguments is invoked. This is useful when you need to use Helm and/or to execute any other command within your k8s cluster context.
If cluster is local, the default configuration is used ($HOME/.kube/config)

If you want to use with helm:

$ gk8s :cluster -- helm <additional-arguments>

Now let's work with multiple clusters on the same command: For example, to compare configurations on two clusters, let's go with diff:

$ colordiff <(gk8s :cluster1 get foo -n bar -o yaml) <(gk8s :cluster2 get foo -n bar -o yaml)

Context switching? Environment variable? You would get quite a lot of troubles here ;)

How to get list of nodes from multiple clusters?

$ parallel 'gk8s {} get nodes' ::: :cluster1 :cluster2 :cluster3

Too many clusters

When you have multiple clusters, you can have multiple configurations and it isn't convenient to have all configuration in the same file and/or same directory.

It's very easy to organize multiple cluster configurations with gk8s. Let's say you're using the default configuration path $HOME/.config/gk8s. You can have directory structure as below

$HOME/.config/gk8s/
  org1/
    cluster1
    cluster2
  org2/
    cluster1
    cluster2
  all
    cluster11 --> ../org1/cluster1 (symlink)
    cluster12 --> ../org1/cluster2 (symlink)
    cluster21 --> ../org2/cluster1 (symlink)
    cluster22 --> ../org2/cluster2 (symlink)

Now everything is quite trivial with gk8s

$ gk8s :org1/cluster1   get nodes
$ gk8s :all/cluster11   get nodes

For mutiple user/context support, you may follow the same way;)

How it works

Each cluster/context has their own configuration file under the directory $GK8S_HOME (which is ~/.config/gk8s/ by default). Working with the cluster is simply by invoking

$ gk8s :<cluster> command-and-or-arguments

for example

$ gk8s :production get pods

would look up configuration in ~/.config/gk8s/production and execute the command kubectl get pods accordingly.

If cluster is local, the command will set KUBECONFIG=$HOME/.kube/config.

If KUBECONFIG file not found, the tool exits immediately.

Authors. License. Misc

The author is Ky-Anh Huynh.

This work is released under a MIT license.

This program is the Golang version of my Bashy thing https://github.com/icy/bashy/blob/master/bin/gk8s. New version is written as an answer to the known problem: Someone really hates Bash :)

icy/gk8s

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