PIGSTY

Etcd

The distributive consensus storage

ETCD is a distributed, reliable key-value store for the most critical data of a distributed system. etcd is used as DCS (Distributed configuration storage) for patroni, the PostgreSQL HA Agent for config management and leader election.

In short, PGSQL depends on a global ETCD module, and ETCD depends on NODE module to work properly (use the node CA).