rebuildFullExtent updated superblock.WALCheckpointLSN but not the
flusher's internal checkpointLSN. NewReplicaReceiver then read
stale 0 from flusher.CheckpointLSN(), causing post-rebuild
flushedLSN to be wrong.
Added Flusher.SetCheckpointLSN() and call it after rebuild
superblock persist. TestRebuild_PostRebuild_FlushedLSN_IsCheckpoint
flips FAIL→PASS.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Flusher now holds WAL entries needed by recoverable replicas.
Both AdvanceTail (physical space) and checkpointLSN (scan gate)
are gated by the minimum flushed LSN across catch-up-eligible
replicas.
New methods on ShipperGroup:
- MinRecoverableFlushedLSN() (uint64, bool): pure read, returns
min flushed LSN across InSync/Degraded/Disconnected/CatchingUp
replicas with known progress. Excludes NeedsRebuild.
- EvaluateRetentionBudgets(timeout): separate mutation step,
escalates replicas that exceed walRetentionTimeout (5m default)
to NeedsRebuild, releasing their WAL hold.
Flusher integration: evaluates budgets then queries floor on each
flush cycle. If floor < maxLSN, holds both checkpoint and tail.
Extent writes proceed normally (reads work), only WAL reclaim
is deferred.
LastContactTime on WALShipper: updated on barrier success,
handshake success, and catch-up completion. Not on Ship (TCP
write only). Avoids misclassifying idle-but-healthy replicas.
CP13-6 ships with timeout budget only. walRetentionMaxBytes
is deferred (documented as partial slice).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
superMu is mandatory for correctness — all superblock mutation+persist
must be serialized. Remove the nil guard in updateSuperblockCheckpoint
and add SuperMu to all 7 test FlusherConfig sites.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Adds sync.Mutex (superMu) to BlockVol, shared between group commit's
syncWithWALProgress() and flusher's updateSuperblockCheckpoint().
Both paths now serialize superblock mutation + persist, preventing
WALTail/WALCheckpointLSN regression when flusher and group commit
write the full superblock concurrently.
persistSuperblock() also guarded for consistency.
Removes temporary log.Printf lines in the open/recovery path that
were added during BUG-RESTART-ZEROS investigation.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
1. HIGH: LinkedWriteFsync now uses SubmitLinkRequests (IOSQE_IO_LINK)
instead of SubmitRequests, ensuring write+fdatasync execute as a
linked chain in the kernel. Falls back to sequential on error.
2. HIGH: PreadBatch/PwriteBatch chunk ops by ring capacity to prevent
"too many requests" rejection when dirty map exceeds ring size (256).
3. MED: CloseBatchIO() added to Flusher, called in BlockVol.Close()
after final flush to release io_uring ring / kernel resources.
4. MED: Sync parity — both standard and io_uring paths now use
fdatasync (via platform-specific fdatasync_linux.go / fdatasync_other.go).
Standard path previously used fsync; now matches io_uring semantics.
On non-Linux, fdatasync falls back to fsync (only option available).
10 batchio tests, all blockvol tests pass.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
New package batchio/ with BatchIO interface (PreadBatch, PwriteBatch,
Fsync, LinkedWriteFsync) and standard sequential implementation.
Flusher refactored to use BatchIO: WAL header reads, WAL entry reads,
and extent writes are now batched through the interface. With the
default NewStandard() backend, behavior is identical to before.
UseIOUring config field added for future io_uring opt-in (Linux 5.6+).
9 interface tests, all existing blockvol tests pass unchanged.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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>
