Sparse delta-file snapshots with copy-on-write in the flusher.
Zero write-path overhead when no snapshot is active.
New: snapshot.go (SnapshotBitmap, SnapshotHeader, delta file I/O)
Modified: flusher.go (flushMu, CoW phase in FlushOnce, PauseAndFlush)
Modified: blockvol.go (Create/Read/Delete/Restore/ListSnapshots, recovery)
Modified: wal_writer.go (Reset for snapshot restore)
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Add SimulatedMaster test helper + 20 assignment sequence tests (8 sequence,
5 failover, 5 adversarial, 2 status). Add BlockVolumeStatus struct and
Status() method. Includes QA test files for CP1-CP4a. 940 total unit tests.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Add master-driven lifecycle operations: promotion, demotion, rebuild,
and split-brain prevention. All testable on Windows with mock TCP.
New files:
- promotion.go: HandleAssignment (single entry point for role changes),
promote (Replica/None -> Primary with durable epoch), demote
(Primary -> Draining -> Stale with drain timeout)
- rebuild.go: RebuildServer (WAL catch-up + full extent streaming),
StartRebuild client (WAL catch-up with full extent fallback,
two-phase rebuild with second catch-up for concurrent writes)
Modified:
- wal_writer.go: ScanFrom() method, ErrWALRecycled sentinel
- repl_proto.go: rebuild message types + RebuildRequest encode/decode
- blockvol.go: assignMu, drainTimeout, rebuildServer fields;
HandleAssignment/StartRebuildServer/StopRebuildServer methods;
rebuild server stop in Close()
- dirty_map.go: Clear() method for full extent rebuild
32 new tests covering WAL scan, promotion/demotion, rebuild server,
rebuild client, split-brain prevention, and full lifecycle scenarios.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
