Adds per-replica state reporting in heartbeat so master can identify
which specific replica needs rebuild, not just a volume-level boolean.
New ReplicaShipperStatus{DataAddr, State, FlushedLSN} type reported
via ReplicaShipperStates field on BlockVolumeInfoMessage. Populated
from ShipperGroup.ShipperStates() on each heartbeat. Scales to RF=3+.
V1 constraints (explicit):
- NeedsRebuild cleared only by control-plane reassignment (no local exit)
- Post-rebuild replica re-enters as Disconnected/bootstrap, not InSync
- flushedLSN = checkpointLSN after rebuild (durable baseline only)
4 new tests: heartbeat per-replica state, NeedsRebuild reporting,
rebuild-complete-reenters-InSync (full cycle), epoch mismatch abort.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
pingqiuandClaude Opus 4.6
3e9358f2be