etcd: A highly-available key value store for shared configuration and service discovery.

• Simple : gRPC (http + JSON API)
• Secure: automatic TLS with optional client cert authentication
• Fast: 10,000 writes/sec
• Reliable : Raft algorithm to be properly distributed.

Service Discovery

WAL

TCP ports:

• 2379- client requests
• 2380 - peer to peer communication

etcd cluster runtime configuration file

# cat /run/systemd/system/etcd2.service.d/20-cloudinit.conf
[Service]
Environment="ETCD_ADVERTISE_CLIENT_URLS=http://172.17.8.101:2379"
Environment="ETCD_DISCOVERY=https://discovery.etcd.io/2f2ecec94c245254181243f86e6b78cd"
Environment="ETCD_INITIAL_ADVERTISE_PEER_URLS=http://172.17.8.101:2380"
Environment="ETCD_LISTEN_CLIENT_URLS=http://0.0.0.0:2379,http://0.0.0.0:4001"
Environment="ETCD_LISTEN_PEER_URLS=http://172.17.8.101:2380,http://172.17.8.101:7001"

gRPC