K3s Raspberry Pi 4 Cluster

Do you have an interest in Raspberry Pis and cluster computing? Me too! 

Parts

One thing that I have enjoyed about building the Raspberry Pi cluster is that it's inexpensive to build up over time. 

I bought the Raspberry Pis and the PoE hats from Canakit, and everything else was bought from Amazon. Amazon had higher prices for the Raspberry Pi PoE hat, and didn't have a Raspberry Pi 4B 8GB board available when I first started buying the parts. 

Here is a list of what I bought for the cluster. 

Part	My Choice	Qty	Links
Case	Cloudlet Cluster Case	1	Amazon
Raspberry Pis	RPi 4B+ 8GB	5	Canakit Amazon
PoE Hats	Raspberry Pi PoE HAT	5	Canakit Amazon
SD Cards	SanDisk 128GB microSDXC	5	Amazon
Network Switch	TP-Link 8 Port PoE Switch	1	Amazon
Network Cables	Cat7 1FT Multi-Color	1 x 5pk	Amazon

Case

I used the Cloudlet Cluster Case by C4Labs.

Very tiny, but fulfilling, RPi cluster.

It practically hums like the WOPR!

I found the case by searching on Amazon for "Raspberry Pi Cluster Case', and the Cloudlet Cluster Case was the first result I saw that I really liked. I like the look of the stackable cases, but the Cloudlet Cluster Case reminded me of a very tiny computer rack - it felt right.

The case has mounting boards and hardware for 8 Raspberry Pis. You mount the Raspberry Pi onto the acrylic board, and then the mounting board easily snaps into the case. 

This is great for allowing you to start very small and expand as you would like. The price might seem like a considerable jump from the stackable case options but I still picked the Cloudlet Cluster Case because I think it looks nice, it's very sturdy, and had enough room for the network switch. 

You can also see a blue square in the image above - that's the Blinkstick Square with an enclosure. I plan to set up monitoring for the cluster, and for a variety of webhooks, and use the Blinkstick Square for showing status. I figured I would use white, red, green, blue, and purple to indicate which Pi/Node the status was for. 

 Raspberry Pis

Originally I was going to build a cluster from a couple old Raspberry Pis I have that I hadn't been using, but I bought a Raspberry Pi 4 bundle for my daughter and the performance is so good that I decided to get the newer Pis instead. 

I would have liked to have bought the Raspberry Pis from Amazon, because I appreciate the customer service you get from Amazon. However, I have had great luck with smaller businesses that sell Raspberry Pi products, and usually they have better prices than what you would good from Amazon. Canakit had Raspberry Pi 4B 8GB boards available before Amazon, and the price is about $15 cheaper. Vilros and the PiShop also had Raspberry Pi 4B 8GB boards listed, but had the same price as Canakit.

PoE Hats

I found a few PoE hat options, but I went for the official Raspberry Pi PoE hat. 

The price was better than most options, and I assumed there would be more testing around the official option. Also, one PoE hat that I looked at seemed to have a nicer profile but the seller suggests buying a fan for it. The official Raspberry Pi PoE hats come with fans attached and there is no issues with clearance in the Cloudlet Case. 

SD Cards

I bought 128 GB SD cards for each of the Pis. I didn't need SD cards that hold that much data because I can attach an external HDDs or SSDs to add storage. If I were to do this again, then I think I would buy smaller SD cards, and use the saved money to go towards external drives.

Network Switch

I bought an 8 port PoE switch from TPLink mainly because it was the cheaper option between it and a Netgear 8 port PoE switch. The TPLink switch is $30 cheaper than the Netgear equivalent. I had no problems at all - it works great with the Raspberry Pi PoE hats. There were no special configurations for the Raspberry Pi, no jumper settings for the PoE hat, and nothing to configure for the switch. Just connect all the things.

There will be a post coming soon that will list the steps I took to set up the Raspberry Pis and get K3s installed. It was relatively simple, but not completely hassle-free. The first time I was able to see that all nodes were running and available to the cluster made it worth it. 

Welcome to 2020! Err...I mean, welcome to August 2020!

I love home projects where the main purpose is to learn something new. The only projects I love more are the next learning projects.

Here are some areas I want to learn more about:

• Kubernetes
• Tracking useful metrics
• For the near future:
• Serverless for Kubernetes
• Load testing at a small scale
• Data pipelines

Some of the items are very easy to explore at work but not all of them, so I plan to focus on projects that are not work specific.

Kubernetes

You might ask, "Who isn't using Kubernetes?"

Well, I wasn't until recently!

It's been really fun. There are so many open-source projects that I want to use that will easily run on Kubernetes that it's almost hard to force myself to start at the beginning and learn how to set up and manage a cluster. Or even a tiny cluster - but that's what I'll do first!

I had wanted to make a Raspberry Pi cluster for a while and this provided the excuse. I bought some Raspberry Pis, a nice case, an unmanaged switch that had 8 PoE ports, PoE hats for the Raspberry Pis, SD cards, and network cables. I put the Pis in the case, installed k3s (Lightweight Kubernetes), and now I just need some projects to help provide areas to start digging!

I'll share the steps I followed, parts I used for putting the cluster together, and anything I might do differently if I were to start over in the near future.

Tracking Useful Metrics

One of my first plans for the cluster will be to add metric tracking. I'm not sure what metric tracking options there are, so I searched to find out what other people are using. I found a number of references to this cluster-monitoring repo, and it looks like the setup for k3s is very simple. I forked and cloned that repo, followed the quick start info for k3s (updated some configs), and Prometheus, AlertManager, and Grafana were soon available and showing some useful metrics!

I'll create a post about what I learn with monitoring in the near future. 

Recommendations:

Following the Quickstart for K3s from the carlosedp/cluster-monitoring repo was very straightforward, and it would be my suggested monitoring choice to anyone setting up a Raspberry Pi based Kubernetes cluster. I might change my mind, but for now it seems like an easy and quick way to go.

For now I suggest forking the repo, and then push any changes you make to vars.jsonnet to your cluster-monitoring repo. That way you can add/remove monitoring for your cluster quickly using a script that clones your repo first.

Near Future Projects

There are a number of things that I want to explore at home:

• Serverless options for Kubernetes (for example, OpenFaaS, KNative, and Kubeless)
• Load testing at a small scale (for example, run load tests against a single service as part of a CI pipeline, or run a set of load tests against a smaller version of your production environment)
• Explore a variety of data pipelines