ClusterNode hosts a BTreeMap<ShardId, Arc<ShardReplica>>: writes hash-route
to the owning shard leader, reads scatter over shard groups. In-group
shard==region preserved so the engine and tidal-net are untouched; S=1 stays
byte-for-byte (today's cluster is a 1-shard × RF=N group). Topology grows
shard-group awareness; membership, election, forward, reseed, and join_boot
thread ShardId through.
Proven by an in-process 2×2 RF=2 gRPC test plus S=1 parity, incl. tier-3
real-OS-process failover. clippy/fmt clean.
Kind-3 term markers in the WAL stream, STREAM-relative vote frontiers,
heartbeat-only divergence detection + quarantine, and fenced promote.
Elections converge in 0.6–1.0s; zero acked-write loss across all kill points.
Closes G5 (leaderless recovery) from the v0.9 wave.
WAL segment format: 8-byte TSEG header (magic + version byte + 3 reserved)
prepended to every new segment. Legacy headerless segments (m0-m11p3) read
as implicit v0 — no migration. Unknown magic/version surfaces as
WalError::SegmentFormatUnknown at open time; foreign files are never
repaired or truncated (fixes the silent data-loss path from the p3 rollout
incident where torn-tail repair zeroed a follower's unreadable segments).
Catch-up transport: FAILED_PRECONDITION ("snapshot required") and stream
errors that skip the shard now arm a timer retry (re-arm-on-skip is the
load-bearing liveness fix — without it a skipped pull never re-fires and
the follower stays permanently behind). Single retry pending per shard;
CatchupRunner owns the Arc'd state shared between the retry tasks and the
transport. Test: tidal-net/tests/catchup_retry.rs covers the retry path.
Stress: k8s stress-job-t2a/t2b yaml + ops/stress-test-p3-t2 runbook.
ack=quorum gates replicated writes on a majority of the replica set durably
holding them: followers push their durably-applied frontier (ReportApplied,
once per apply round, decoupled from ship acks), the leader folds frontier
reports + ship-ack hints + heal resumes into a leadership-scoped CommitIndex
(k-th-largest durable mark), and handlers await it through an async
watch-channel bridge (zero parked threads per waiter). Honest timeouts:
retryable 503 naming the laggards; x-tidal-seq on every cluster write.
Follower blob applies are batched under group-commit fsyncs (22x seeding).
Exit gate: 167/167 leader-SIGKILL kill points, zero acked-write loss.
Seven-dimension review pass (all confirmed findings fixed):
- WAL blob drain now ABORTS on the first write failure instead of reusing
the failed seqno mid-drain (a torn record buried mid-segment would
truncate every later acked record on replay)
- apply_replicated_blobs waits every staged append even after a mid-batch
failure, parses metadata once, and moves records into Arcs shared with
the WAL writer (no deep clone per record on the follower apply path)
- CommitIndex: zero-peer fast path now respects demotion (active checked
under lock before the single-replica return), k-th-largest uses
select_nth over a reused scratch buffer
- await_quorum: re-reads the index once after the deadline fires (no false
503 for a write that committed in the race window), warns when the
commit-watch bridge dies outside shutdown, zero-peer path checks active
- notify_applied report failures: WARN on the first failure of a streak,
INFO on recovery (a silently stalling frontier reads as unexplained
quorum 503s); receiver skips re-notifying unadvanced frontiers
- x-tidal-deduplicated: 1 marks dedup-suppressed signal writes (relayed
through forwards) so durability cursors can tell dedup from no-seqno
- docs: 167/167 kill-point record corrected in CHANGELOG; rolling-upgrade
order (leader first — a pre-m11p3 leader silently downgrades quorum
requests to leader-ack) in CHANGELOG + runbook §8; monitoring note for
report-loss diagnosis on the quorum-timeout alert
Verified: workspace clippy -D warnings (incl. cluster-e2e targets), full
tidaldb/tidal-net/tidal-server/tidalctl suites green, tier-3 multi-process
quorum suite green (8/8 kill points, zero acked loss, partition gate/recover).
m11p1 — decoupled ack/ship path: staged writes (seqno+WAL+relay-push,
microseconds) separate from group-commit fsync; ShipQueue batches+windows
outbound segments; receiver coalesces inbound chunks before applying.
Adds first tidaldb_cluster_* metrics.
m11p2 — leader WAL is now THE replicated log: fsynced batches feed a
bounded WalShipFeed and ship byte-identical to followers; WAL seqnos
survive restarts (relay-reset hazard gone). Item metadata and embeddings
journal kind-1/2 blob records on the same stream as signals; the m8p10
HTTP broadcast is deleted. StreamSegments catch-up is follower-pulled via
server-streaming RPC, triggered on gap detection, follower boot, and
leader heal nudge. Promote carries a stream baseline so peers skip
pre-stream history.
Splits monolithic cluster.rs into tidal-server/src/cluster/ modules. Adds redeliver-missed
relay, bounded HLC drift, lag tracking, and reconcile idempotence. Five new tier-3 test suites
(chaos, lifecycle, multiproc, region, routes, runbook) all green. Docs, CHANGELOG, and ROADMAP
updated with G4/G5/G6 known gaps.
