The metadata engine

These pages describe what the Master Server holds, what it records, and what it needs to pass the whole set to another server.

What metadata holds and what it costs in RAM lists the kinds of record in the metadata and the size of each. Changelogs, dumps, and the recovery point describes the same structure on disk: what is written, when, what a startup reads back, and how much work a sudden failure costs. Metadata save states covers what each server reports about its own last save. Metadata ID, version, delay, and checksum covers the four numbers that show whether two copies of the metadata are the same set in the same state.

Leader election, quorum, and the role of DNS describes the state machine that every Master Server runs: what changes the role of a server, who orders the change, and what the change does to the connections. Leader-Follower synchronization describes how the metadata itself is sent between Master Servers.