Adds the sync_all reconnect protocol: when a degraded shipper
reconnects, it performs a handshake (ResumeShipReq/Resp) to
determine the replica's durable progress, then streams missed
WAL entries to close the gap before resuming live shipping.
New wire messages:
- MsgResumeShipReq (0x03): primary sends epoch, headLSN, retainStart
- MsgResumeShipResp (0x04): replica returns status + flushedLSN
- MsgCatchupDone (0x05): marks end of catch-up stream
Decision matrix after handshake:
- R == H: already caught up → InSync
- S <= R+1 <= H: recoverable gap → CatchingUp → stream → InSync
- R+1 < S: gap exceeds retained WAL → NeedsRebuild
- R > H: impossible progress → NeedsRebuild
WALAccess interface: narrow abstraction (RetainedRange + StreamEntries)
avoids coupling shipper to raw WAL internals.
Bootstrap vs reconnect split: fresh shippers (HasFlushedProgress=false)
use CP13-4 bootstrap path. Previously-synced shippers use handshake.
Catch-up retry budget: maxCatchupRetries=3 before NeedsRebuild.
ReplicaReceiver now initializes receivedLSN/flushedLSN from volume's
nextLSN on construction (handles receiver restart on existing volume).
TestBug2_SyncAll_SyncCache_AfterDegradedShipperRecovers flips FAIL→PASS.
All previously-passing baseline tests remain green.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Replaces binary degraded flag with ReplicaState type:
Disconnected, Connecting, CatchingUp, InSync, Degraded, NeedsRebuild.
Ship() allowed from Disconnected (bootstrap: data must flow before
first barrier) and InSync (steady state). Ship does NOT change state.
Barrier() gating:
- InSync: proceed normally
- Disconnected: bootstrap path (connect + barrier)
- Degraded: reconnect both data+ctrl connections, then barrier
- Connecting/CatchingUp/NeedsRebuild: rejected immediately
Only barrier success grants InSync. Reconnect alone does not.
IsDegraded() now means "not sync-eligible" (any non-InSync state).
InSyncCount() added to ShipperGroup.
dist_group_commit.go: removed AllDegraded short-circuit that
prevented bootstrap. Barrier attempts always run — individual
shippers handle their own state-based gating.
8 CP13-4 tests + TestBarrier_RejectsReplicaNotInSync flips FAIL→PASS.
All previously-passing baseline tests remain green.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Adds sync.RWMutex (ioMu) to BlockVol enforcing mutual exclusion
between normal I/O and destructive state operations.
Shared (RLock): WriteLBA, ReadLBA, Trim, SyncCache, replica
applyEntry, rebuild applyRebuildEntry — concurrent I/O safe.
Exclusive (Lock): RestoreSnapshot, ImportSnapshot, Expand,
PrepareExpand, CommitExpand, CancelExpand — drains all in-flight
I/O before modifying extent/WAL/dirtyMap.
Scope rule: RLock covers local data-structure mutation only.
Replication shipping is asynchronous and outside the lock, so
exclusive holders block only behind local I/O, not network stalls.
Lock ordering: ioMu > snapMu > assignMu > mu.
Closes the critical ER item: restore/import vs concurrent WriteLBA
silent data corruption gap.
3 new tests: concurrent writes allowed, real restore-vs-write
contention with data integrity check, close coordination.
Co-Authored-By: Claude Opus 4.6 (1M context) <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>
Primary ships WAL entries to replica over TCP (data channel), confirms
durability via barrier RPC (control channel). SyncCache runs local fsync
and replica barrier in parallel via MakeDistributedSync. When replica is
unreachable, shipper enters permanent degraded mode and falls back to
local-only sync (Phase 3 behavior).
Key design: two separate TCP ports (data+control), contiguous LSN
enforcement, epoch equality check, WAL-full retry on replica,
cond.Wait-based barrier with configurable timeout, BarrierFsyncFailed
status code. Close lifecycle: shipper → receiver → drain → committer →
flusher → fd.
New files: repl_proto.go, wal_shipper.go, replica_apply.go,
replica_barrier.go, dist_group_commit.go
Modified: blockvol.go, blockvol_test.go
27 dev tests + 21 QA tests = 48 new tests; 889 total (609 engine + 280
iSCSI), all passing.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
