Why is quorum needed in etcd for Patroni?

The quorum in etcd for Patroni is necessary to ensure the consistency and reliability of the PostgreSQL cluster.

Patroni uses etcd as a distributed configuration store and leader election mechanism. Quorum is the minimum number of etcd nodes that must agree on changes for the operation to be considered successful.

This prevents split-brain situations, where multiple nodes might simultaneously consider themselves leaders, which could lead to data loss or inconsistency.

Therefore, quorum guarantees that only one Patroni node will be the leader at any given time, ensuring the integrity and fault tolerance of the cluster.