Spawn a shell for a particular kubectl context (cluster).

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kubesh

Synopsis

kubesh --context=name-of-context

Installation

TODO: I am not sure if this is the best way. Patches welcome

$ git clone [email protected]:lestrrat/kubesh.git ~/.kubesh

Then add PATH to ~/.kubesh/bin

export PATH="~/.kubesh/bin:$PATH"

Description

When you are using multiple clusters, you normally use kubectl config use-context to change which cluster (and assocaited configuration) we use. The problem with using contexts this way is that changes are global: You use use-context in one terminal, and the changes are observed in another terminal as well.

So what happens when you want to work on one cluster which also depents on another cluster, and you want to be monitoring both?

This is where kubesh comes in. It does not force you to create multiple KUBE_CONFIGs, and it allows you to keep working on the same context for the duration of the shell session, and you do not have to explicitly set the context by yourself.

Using Multiple GCP Accounts

If you are using multiple accounts to control multiple accounts on GCP, you may run into problems switching your context.

Currently, there are only two ways I know that really works for working with multiple accounts.

1. Add Your Main-Account As A Member Of Your Sub-Account

Configure your project so that your main account is a member of the project for your sub-account. May have security implications, but it's easy.

2. Modify ~/.kube/config By Hand

This has proven to be sometimes problematic, possibly because of caching. It seemd to work for me when I started with a fresh ~/.kube/config file.

The way kubectl gets tokens is by invoking gcloud config config-helper. How this command is invoked is stored in ~/.kube/config file, like so:

- name: gke_project_zone_cluster
  user:
    auth-provider:
      config:
        cmd-args: config config-helper --format=json
        cmd-path: /usr/local/google-cloud-sdk/bin/gcloud
        ...

You can change tell gcloud config config-helper to work with a particular GCP configuration by setting the --configuration parameter. So you could do something like below:

- name: gke_project_zone_cluster_A
  user:
    auth-provider:
      config:
        cmd-args: config config-helper --format=json --configuration=A
        cmd-path: /usr/local/google-cloud-sdk/bin/gcloud
- name: gke_project_zone_cluster_B
  user:
    auth-provider:
      config:
        cmd-args: config config-helper --format=json --configuration=B
        cmd-path: /usr/local/google-cloud-sdk/bin/gcloud
        ...

This will then force kubectl to use different configurations when generating access tokens

Integration With `peco`

If you are too lazy to type the context name, you can integrate it with peco

function peco-kubesh() {
    local selected=$(kubectl config get-contexts | sed -e 's/\*//' | awk 'NR < 2 { next } {print $1}' | peco)
    ST=$?
    if [[ $ST != 0 ]]; then
        exit 1
    fi
        
    if [ -n "$selected" ]; then
        kubesh --context=$selected
    fi  
}

zle -N peco-kubesh

Support For Other Utilitites

helm: helm since 2.0.0 supports --kube-context argument, and we provide support for it.

stern: stern supports switching contexts, and we provide support for it.

kubefed: --host-cluster-context is populated with the value you passed to --context.

Caveats

As of this writing, it only works for zsh. Because we spawn a new shell, we need to stop the newly created shell from reading the rcfiles again, but I could not find a portable way to do it. Patches welcome.

If kubectl ever supports KUBE_CONTEXT environment variable, this utility probably be deprecated.

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