Finish my Raspberry Pi Zero Cluster... complete with kubernetes, etc.

... I still don't know what I'm going to run on this. suggestions in the comments welcome.

My weekend project. Anyone else built a Raspberry Pi 3 cluster (for Kubernetes)?

It seems that every Pi day, I end up with a new Raspberry Pi that I got sometime before it. First, a 1, then a 2+3, now I have a Zero as well. Next year, I'll have a cluster of 3s. No reason, just want to mess with it.

So for a while I have wanted to build a raspberry pi cluster. In the spirit of shia labeouf I got started last saturday.

I had two pies lying around so I figured I'd run some experiments before I invested in a lot of hardware. After about a day I had turned the two pies into a shared cluster when disaster struck....

I had completely ignored the fact that you cannot run 32 or 64bit software on an arm processor (I know... I'm a java developer). So when I booted my service and the load balancer, I found that nothing worked. So pretty bumbed out, I quit the project.

Later that day I found a crazy guy who had bought a batch of 400 small form factor PSUs (300W) and internally I laughed at him a little. I mean, who's gonna sell 300W irregular power supplies. Then, just as I was about to go to bed I found this guy, he was selling from a batch of CPU-onboard motherboard for 10 bucks each and everything clicked!

I did some quick calculations and decided I could probably gather enough cash to get: 10 motherboards, 10 2GB ram dimms, 10 Sata disks and 14 PSU (in case some fail) and some misc hardware for networking and such.

So... Long story short, I am going to build a cluster computer, the first version is going to have 10 nodes and I am waiting for delivery right now!

I really want to build a raspberry pi cluster but I don't know what to do with it...
Has anyone of you ever built a raspi cluster?
What could I do with it?

Finally set up my 5-node Raspberry Pi Kubernetes cluster.

## Learning k8s

Interesting. So sometimes k8s network goes down. Apparently it's a pitfall that has been logged with vendor but not yet fixed. If on either of the nodes networking service is restarted (i.e. you connect to VPN, plug in an USB wifi dongle, etc..) -- you will lose the flannel.1 interface. As a result you will NOT be able to use kube-dns (because it's unreachable) not will you access ClusterIPs on other nodes. Deleting flannel and allowing it to restart on control place brings it back to operational.

And yet another note.. If you're making a k8s cluster at home and you are planning to control it via your lappy -- DO NOT set up control plane on your lappy :) If you are away from home you'll have a hard time connecting back to your cluster.
A raspberry pi ir perfectly enough for a control place. And when you are away with your lappy, ssh'ing home and setting up a few iptables DNATs will do the trick

netikras@netikras-xps:~/skriptai/bin$ cat fw_kubeadm
#!/bin/bash

FW_LOCAL_IP=127.0.0.15
FW_PORT=6443
FW_PORT_INTERMED=16443
MASTER_IP=192.168.1.15
MASTER_USER=pi

FW_RULE="OUTPUT -d ${MASTER_IP} -p tcp -j DNAT --to-destination ${FW_LOCAL_IP}"

sudo iptables -t nat -A ${FW_RULE}

ssh home -p 4522 -l netikras -tt \
-L ${FW_LOCAL_IP}:${FW_PORT}:${FW_LOCAL_IP}:${FW_PORT_INTERMED} \
ssh ${MASTER_IP} -l ${MASTER_USER} -tt \
-L ${FW_LOCAL_IP}:${FW_PORT_INTERMED}:${FW_LOCAL_IP}:${FW_PORT} \
/bin/bash
# 'echo "Tunnel is open. Disconnect from this SSH session to close the tunnel and remove NAT rules" ; bash'

sudo iptables -t nat -D ${FW_RULE}

And ofc copy control plane's ~/.kube to your lappy :)

Sophomore year starting soon so I'm looking for new project (s) to complete in parallel with the studies.
Some are more design-y and some more backend-y but I recently started getting better at designing so :)

1) Learn some fragment shader stuff. I've always been messing around with graphics and have a game on steam, so I think that's a good idea to be paired with signal processing.

2) Reactive web services. Preferably with spring-boot or vert.x but

3) I would also like to dive into golang (and make some reactive thing with it)

4) WebAssembly seems nice... But I got some concerns

5) exercise making wireframes -> CSS (with some js)

6) I've never really done any real backed work with nodejs, except serving and aot compiling js, or doing gulp tasks

7) Implementing a whole project, or a fraction of it as serverless on aws

* I'm definitely going to use a couple very simple services to make a docker swarm with load balancing, etc, just because I know how everything works but got no practical knowledge

8) Design an esports jersey for the university department I'm in (shouldn't take long)

So what do you guys think? Recommendations are welcome :)

P.S. last year in review:
> A webapp running on a raspberry pi powering a reflex testing game on gpio (java/spring-boot , codename: buttonmasher)
> small Elastic search cluster to monitor some random university servers through kibana dashboards
> laser tracking on wall of *any* colour and variable light conditions via a webcam (opencv) , controlling the mouse pointer, whether you run it against a projector or any wall
> jstrain.herokuapp.com => a small JavaScript powered tool with a DSL to help you train more efficiently without a coach
> Various random Photoshop stuff