I recently blogged about a small game I made that interfaces with any Kubernetes cluster and allows you to enter cluster nodes and destroy live, running pods.
I mentioned I would make the source available if there was any interest, so here it is.
After a little bit of code clean-up, and removing my 2D Shooter Bullet and Weapon System and 2D Neon Grid asset code from the game, the source is now available. These modules are game development modules/assets that I sell on the Unity Asset Store, and as such could not include in the source here. The fancy grid/background effect is therefore missing in this version.
I’ve also added an initial Windows build in the releases section, which is ready to go. Just unzip, run and enter your kube context/namespace details to get going.
If you decide to compile from source yourself, just make sure you have Unity 2019.4 or later installed and you should be good to go. I’ve not yet tested on macOS or Linux, but
I enjoy game development as a hobby on the side. I also enjoy working with container schedulers like Kubernetes. Over the weekend I decided to create a Kubernetes game, combining those two thoughts.
In the game you enter and explore nodes in your cluster, and can destroy your very own live, running pods. Hide prod away!
The game is put together using my engine of choice, Unity. With Unity you code using C#.
3 x Nodes represented in-game from my Raspberry Pi Kubernetes cluster. Can you spot the naming convention from one of my favourite movies?
Game Logic
The game logic was simple to put together. I have a couple of modular systems I’ve already developed (and actually sell on the Unity Asset Store), so those made the movement and shooting logic, as well as background grid effects a breeze.
Movement is implemented in a simple ‘twin-stick’ controller Script (a Unity concept, which is a class implementing Monobehaviour).
Other game logic is mostly contained in the bullet pattern module. I have some more Scripts that arrange and control the Kubernetes entities as well as their labels.
The interaction with Kubernetes itself is fairly hacked together. I wanted to put the game together as quickly as possible as I only worked on it over a couple of weekend evenings.
Let the hacky code flow…
Unity is a bit behind in .NET Framework version support and .NET Core was out of the question. This meant using the Kubernetes csharp client was not going to happen easily (directly in Unity that is). It would have been my first choice otherwise.
With that in mind, I skipped over to a hacky solution of invocating the kubectl client directly from within the game.
The game code executes kubectlcommands on threads separate to the main game loop and returns the results formatted accordingly, back to the game’s main thread. I used System.Diagnostics.Process for this.
From there, game entities are instantiated and populated with info and labels. (E.g. the nodes and the pods).
Pods have health
Pods are given health (hit points) and they simply bounce around after spawning in. You can chase after and shoot them, at which point a kubectl destroy pod command is actually sent to the Kube API via kubectl!
The game world
You enter the world in a ‘node’ view, where you can see all of your cluster’s nodes. From there you can approach nodes to have them slide open a ‘door’. Entering the door transports you ‘into’ the node, where you can start destroying pods at will.
For obvious reasons I limit the pods that are destroyable to a special ‘demo’ namespace.
Putting together the demo pods
I use a great little tool called arkade in my Kubernetes Pi cluster.
arkade makes it really simple to install apps into your cluster. Great for quick POCs and demos.
Arkade offers a small library of useful and well thought out apps that are simple to install. The CLI provides strongly-typed flags to install these apps (or any helm charts) in short, one-line operations.
It also handles the logic around figuring out which platform you’re running on, and pulling down the correct images for that platform (if supported). Super useful when you’re on ARM as you are with the Raspberry Pi.
Straight from the GitHub page, this is how simple it is to setup:
# Note: you can also run without `sudo` and move the binary yourself
curl -sLS https://dl.get-arkade.dev | sudo sh
arkade --help
ark --help # a handy alias
# Windows users with Git Bash
curl -sLS https://dl.get-arkade.dev | sh
I then went about installing a bunch of apps and charts with arkade. For example:
arkade install loki --namespace demo
Hooking the game up to my Kube Cluster
With the demo namespace complete, and the application pods running, I needed to get my Windows machine running the game talking to my Pi Cluster (on another local network).
I have a Pi ‘router’ setup that is perfectly positioned for this. All that is required is to run a kube proxy on this, listening on 0.0.0.0 and accepting all hosts.
I setup a local kube config pointing to the router’s local IP address on the interface facing my Windows machine’s network, and switched context to that configuration.
From there, the game’s kubectl commands get sent to this context and traverse the proxy to hit the kube API.
Destroying pods sure does exercise those ReplicaSets!
ReplicaSets spinning up new pods as quickly as they’re destroyed in-game!
Source
If there is any interest, I would be happy to publish the (hacky) source for the main game logic and basic logic that sends the kubectl processes off to other threads.
