In [this post]({% post_url 2022/2022-12-22-erlang-cluster-k8s-ssh %}), we explored a method to access the Erlang console via SSH using kubectl port-forward. While functional, the process involves multiple steps and commands, making it less than ideal for quick access. Wouldn’t it be convenient to have a one-step solution by running a simple command like kubectl ssh POD? Let’s dive into creating a kubectl plugin for seamless pod access.

Simplifying with kubectl Plugins

Implementing a kubectl plugin is quite straightforward. By placing the plugin script in your $PATH, you can invoke it as a regular kubectl command. Consider the simple kubectl-hello plugin script below:

#!/usr/bin/env bash
echo "Hello kubectl!"

Running kubectl hello after marking the script as executable will output Hello kubectl! with ease.

Crafting the kubectl ssh Plugin

To streamline pod access, we can create a kubectl-ssh script that automates the port forwarding and SSH connection process. By using redirection and proper scripting, the plugin can efficiently handle the necessary steps. Below is a snippet demonstrating the kubectl-ssh script:

#!/usr/bin/env bash

exec 3< <(kubectl port-forward "$@" 0:22)

# When the script exits, kill the port-forward process
pid=$!
trap "kill $pid" EXIT

# Extract the local port number
read <&3 -r line

re='^Forwarding from .*:([0-9]+) -> 22$'
if [[ $line =~ $re ]]; then
    port="${BASH_REMATCH[1]}"

    # Connect to the local port using SSH; disable host key validation
    ssh -p "$port" -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null localhost
else
    exit 1
fi

By making this script executable and placing it in your $PATH, you’ll have a simplified way to SSH into pods.

Enhancing with Tab Completion

Since version 1.26.0, kubectl supports tab completion for plugins, optimizing the user experience. To enable this feature, create a kubectl_complete-ssh script as shown below:

#!/bin/sh

exec kubectl __complete port-forward "$@"

With this script in place and appropriately configured, you can leverage tab completion seamlessly.

By creating a kubectl ssh plugin, you can significantly improve your workflow efficiency when interacting with pods in Kubernetes. This streamlined approach simplifies the process, making pod access hassle-free and more intuitive for users.

For the full source code of the kubectl-ssh script and further details, you can visit the repository here.

Remember to stay informed about any platform-specific considerations, as highlighted in the blog post.

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Let’s create a seamless kubectl ssh plugin for easy pod access!