2 minutes
etcd
setup
i have 3 VMs: vm1, vm2 and vm3
| Node | IP Address |
|---|---|
| node1 | 172.31.253.147 |
| node2 | 172.31.250.205 |
| node3 | 172.31.253.194 |
step1: Install etcd on ALL 3 Nodes and create the data dir
let’s verify the version and create the data directory
step2: Create the etcd systemd Service
we do the same thing for other VMs changing just the ip add for example for node1
cat << 'EOF' | sudo tee /etc/systemd/system/etcd.service
[Unit]
Description=etcd
Documentation=https://github.com/etcd-io/etcd
After=network.target
[Service]
Type=notify
ExecStart=/usr/local/bin/etcd \
--name=etcd-1 \
--data-dir=/var/lib/etcd \
--listen-peer-urls=http://172.31.252.48:2380 \
--listen-client-urls=http://172.31.252.48:2379,http://127.0.0.1:2379 \
--advertise-client-urls=http://172.31.252.48:2379 \
--initial-advertise-peer-urls=http://172.31.252.48:2380 \
--initial-cluster=etcd-1=http://172.31.252.48:2380,etcd-2=http://172.31.250.205:2380,etcd-3=http://172.31.253.194:2380 \
--initial-cluster-token=k8s-etcd-cluster \
--initial-cluster-state=new
Restart=on-failure
RestartSec=5
[Install]
WantedBy=multi-user.target
EOF
–name: is the identity of this node in the cluster –data-dir: where etcd stores all data on disk –listen-peer-urls port 2380: talk to OTHER etcd nodes (Raft) …
start the service
let’s reload and start etcd on all nodes
sudo systemctl daemon-reload
sudo systemctl enable etcd
sudo systemctl start etcd
now let’s see the Raft election on logs
but wait wait -> what is the Raft election ? see this
sudo journalctl -u etcd -f
let’s see if the cluster is healthy
etcdctl \
--endpoints=http://172.31.253.147:2379,http://172.31.250.205:2379,http://172.31.253.194:2379 \
endpoint health
let’s check the leader
btw you can run it where ever you want
etcdctl \
--endpoints=http://172.31.253.147:2379,http://172.31.250.205:2379,http://172.31.253.194:2379 \
endpoint status --write-out=table
Phase 2 — Talk to etcd Directly
now we’ll do the job of apiserver
let’s put and get from the leader .147
etcdctl \
--endpoints=http://172.31.253.147:2379 \
put /registry/pods/default/nginx '{"kind":"Pod","name":"nginx"}'
=> ok
etcdctl \
--endpoints=http://172.31.253.147:2379 \
get /registry/pods/default/nginx
=> {“kind”:“Pod”,“name”:“nginx”}
now let’s read from a follower like node2 so this is the magic of Raft
we put it on node1 -> we get it from node2 or 3
to be continued …