Malachi.
View Source
A ra (Raft) state machine that replicates Malachi.Metadata.
ra's apply/3 delegates to the pure, deterministic Metadata.apply/3, exactly the
contract the metadata machine was designed for, so the control-plane metadata becomes
durable and Raft-replicated with no change to the business logic. The clock it hands over is
meta.system_time, the timestamp the leader wrote into the log entry: the same on every replica
and on every replay, which is what lets a registered segment carry its opened_at without the
command carrying it. One ra cluster
backs one DS-RSM vnode; leadership of that cluster is the vnode's coordinator.
Determinism is what makes this safe: every replica applies the same command log and
reaches the same Metadata state (the property the MetadataPropertyTest pins down).
Versioned through Malachi.Cluster.MachineVersion: a command above the group's effective
machine version, or one this code does not know, is refused identically on every replica.