Infrastructure

Apache ZooKeeper

How Apache ZooKeeper connects to the rest of the stack: what it depends on, what depends on it, and what it is commonly deployed alongside.

Concepts it implements

A majority of members must agree before a decision stands, which is what stops two halves of a partitioned cluster both acting as leader.

An algorithm by which unreliable nodes agree on a single ordered history, usually Raft or Paxos in practice.