Root cause (found via ha-convergence-recovery task 8 live 3-node E2E): a
controller with no local config (config_version_tag==0) could become PRIMARY
and push an empty config, breaking replication.
Two upstream election-safety gaps, both outside ha-convergence-recovery:
1. RDHUP re-election bypassed the no-config 'voter only' guard. The startup
path (ha_start_election_async) refuses to start an election when
my_config_tag==0 && n_peers>1, but the RDHUP failover path
(ha_on_primary_ctrl_fd_rdhup) called raft_on_leader_lost unconditionally.
Fix: mirror the guard before elect_ctx alloc / hook / raft_on_leader_lost;
a config-less node stays CTRL_STANDBY (voter only) and grants the
configured peer instead of starting (and winning) its own election.
2. Voter freshness gate compared the candidate only against the voter's LOCAL
config, ignoring the cluster's known committed state. Fix: ha_vote_self_freshness
floors the comparison at max(local, learned-committed config_tag / committed_lsn),
so a voter denies any candidate whose config/cluster state is outdated vs
what the cluster has committed. Strictly additive (never denies the freshest
node — Leader Completeness preserves liveness).
TDD: test_rdhup_noconfig_node_does_not_elect + configured-node contrast;
test_ha_vote_gate learned-floor deny + liveness + backward-compat. Full
controller suite green under ASAN. commit.c and ha-convergence-recovery
files untouched.
3 RED carriers (duplicate FINISH on DONE appends a 2nd WAL entry +
overwrites state; START on terminal clobbers it; replay non-equivalent)
+ 2 preservation pins (forward postdone PDONE-merge, fail-after-finish
PERR-merge) that 6.2 must not break. Reviewer-confirmed: the
UPDATE-clears-terminal arm is production-unreachable (pinned, not
driven). 22 tests / 3 RED; census 508 distinct triples, only those 3
fail.
configAck branch: per-push majority (acked_config_lsn >= push_tag,
1+count > n_peers/2 over r->ce->n_peers, n_peers<=1 immediate,
ce==NULL -EINVAL); legacy >0 counting and n_active==0 shortcut dead.
push_config_to_standbys returns the barrier result; upgrade failure ->
send_upgrade_error (rc forwarded), no success ACK, no restart,
committed_config_tag success-only.
Remediation r1 (two CRITICAL review findings):
- F1: wire production config-ACK ingestion — replconfigpushreplymsg
decode branch in repl_ack_decode_and_dispatch -> repl_on_config_ack
on the promoted-vote ep; + defensive cluster.c OPCode_reply case.
Closes the unlanded half of ha-config-bootstrap 8.1; without this the
barrier would brick every multi-member config upgrade. No schema change.
- F2: keep the barrier off the iomgr thread — export
push_config_transport_only (non-blocking) for the 5 ha.c + join.c
streaming sites; barrier path now vtask-only (do_upgrade_config).
Wire-path test drives real capnp ACK bytes through the production decode
branch. 30/30 rollout, 6/6 repl_majority, 46/46 config_repl; census 0
FAIL; pre-existing fixture leak only (less than baseline).
Green integration proof: 4 facts driven during total quorum loss append
RETAIN with rc 0 in <1000ms (vs 5000ms timeout — wrongly-applied WAIT
tripwire), pending with retained-depth=4 logged, present exactly once
on disk (real WAL header scan); reconnect + one covering ACK commits
the suffix with current_lsn unchanged (no redelivery). Completes the
bug-396 fix evidence (umbrella Req 2.8). Census 495/495.
4 RED carriers (notify/update/setpreason/clrpreason must be admitted
without quorum — currently NOT_READY, the bug-396 hole) + 2 pins (six
request opcodes stay rejected; quorum-present admits all ten). Census
494 = 488 + 6; exactly 4 FAILs.
4 green pins: handle_jobdispatch replies receipt-only with zero WAL
appends through a real 2-alloc dispatch cycle (notify outcomes intact,
reply-precedes-processing); set/clr_preason and do_update_op rusage
stay receipt-style with RETAIN-pending fact appends ACK-committed.
Umbrella Reply-Ordering Contract cited per pin. DISCOVERY bug-451
(reviewer-verified): RUSAGE hook va_list type confusion — 4-byte OOB
read + garbage state in WAL_JOB_RUSAGE payloads; fix deferred to 7.1.
Census 488; zero failures.
7 cases: two covered short-circuits, timeout with committed_lsn
unmoved, covering-ACK release, sync_timeout_ms fallback (bounded both
directions), n_peers=1 standalone, NOT_READY passthrough via cap
saturation. Watermark resolved to current_lsn - 1 (design's literal
phrasing unsatisfiable per persist.h:71 invariant) with off-by-one
killing power both ways. 15 tests / 7 RED; suite baseline zero.
Fixed the 3 bug-411 baseline failures honestly: stale timeout
expectation updated to the reject-on-timeout contract (engine-wired
fixture, killing power retained); two healthy-primary gate fixtures
populated with standby_endpoints (gate logic untouched). Census: 46
groups / 467 tests / 0 failures standalone under default ASAN.
Audit (reviewer-confirmed, recorded in tasks.md): no production walAck
path reaches the deprecated acked_lsn>0 counting or n_active==0
short-circuit except the documented LSN-0 first entry. Leak inventory
for 6 groups documented as follow-up.
cluster_t embeds commit_engine_t; init in cluster_init_phase2 after the
vtaskmgr guard (idempotence-guarded — phase2 can run twice), wiring
repl_set_commit_engine + ha.repl back-pointer before any standby can
register; fini after iomgr/vtask shutdown. persist_wal_sync_append
passes written_lsn; engine-wired path drops -ENODEV and the
committed_lsn store (engine owns advancement); LSN-0 first-entry
routes to legacy per the accepted interim. p2 -ENODEV pin updated to
the Req 6.3 contract. 34/34 + 6/6 green through honest delegation;
census exactly at the 3 validated baselines; production binary links.
repl_active_standby_count: registry truth (ep != NULL && !in_catch_up)
under r->lock. ha_state_t gains repl back-pointer (wired at init by
task 5.3); ha_has_write_quorum uses registry truth when wired, exact
legacy fallback when NULL; formula unchanged. Test 29 (wired gate,
catch-up-only standby → NOT_READY, admits after clear) captured RED
pre-fix. 29/29 group tests; suite at the 3-failure baseline.
Tests 21-28: repl_active_standby_count contract (5 RED vs inert -1
stub) + 3 gate-level pins (n_peers<=1 always-true, zero-connected
reject, stateless re-accept) that 4.2 must preserve. Declaration in
repl.h; ha.c/ha.h untouched (4.2 boundary). 28 tests / 5 RED; suite
at the 3-failure baseline with unchanged signatures.
Tests 17-20: catch-up ACK exclusion vs pending waiter, membership-change
wake of covered waiter, removal-below-majority fails at own deadline
(no forced early-fail), non-blocking bound. Landed GREEN: task 1.2's
commit_on_membership_change already implements the full 3.2 contract,
so RED was unachievable; reviewer confirmed mutation-killing power and
zero production changes. 20/20 group tests; suite at baseline.
9 new cases (8-16): block-until-majority, deadline timeout, standalone
fast path, zero-ACK regression, n_vcpus-relative cap with floor, ACK
progress at saturation, gate as blocking predicate (NOT_READY is
admission-cap-only per corrected contract). Main-thread-only assertions
after joins; 16 tests / 9 RED failures; baseline unchanged.
Add test_repl_registration_lifecycle covering the complete 3-step standby
lifecycle: register (nstandbys==1, ep pointer verified), duplicate
(idempotent, same slot), deregister (ep==NULL, nstandbys==0 — the
previously-untested slot-zeroing invariant). Tasks 5.1/5.2 were already
covered by test_broadcast_one_standby_sends_entry, test_wal_wire
round-trip, and test_wal_ack_reply_updates_acked_lsn_and_signals.
18 repl unit tests pass under ASAN.
Fix defective assertion in test_committed_lsn_advances_after_majority_ack
(before/after delta instead of >0 which fails for lsn=0 first write).
Add test_single_node_committed_lsn_unchanged documenting -ENODEV degraded
mode for no-standby path. Fix NACK test expected return from -ETIMEDOUT to
0: with 1 registered standby, quorum=1 is met by primary self-count alone.
308 tests pass, 0 fail under ASAN.
Handle incoming WalAckReply in repl_ack_decode_and_dispatch: extract
lsn+success, call repl_on_ack on success to update standby acked_lsn
and signal majority-ack waiter. NACK is WARN-logged with no state
change. Two unit tests verify positive path (acked_lsn updated, waiter
unblocked) and negative path (NACK leaves acked_lsn=0, wait times out).
Standby sends WalAckReply via xce_reply after each successfully
applied WAL entry. ha_apply_wal_catchup_entry signature extended
with endpoint_t* and cluster_t* parameters. walackreplymsg union
arm added to RequestReply capnp schema and xce_reply_t. Error
entries skip ACK. Dispatch gate test confirms OPCode_walCatchupEntry
allowed in CTRL_STANDBY/ELECTING/INIT.
Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>
Election protocol fixes validated against raft.tla invariants:
- ha_init_raft(): one-time raft state init at startup (re-init would lose
durable election progress); n_peers = full cluster size including self
- handle_request_vote(): higher-term step-down moved BEFORE the role gate
(split-brain fix); standby vote-deny now requires a live primary control
channel (primary_ctrl_fd >= 0) AND a fresh heartbeat
- ha_heartbeat_is_fresh(): derive freshness from ha->last_activity (the
field production actually writes); the orphaned last_heartbeat timespec
had no production writer, leaving the vote-deny gate inert (bug-337);
field removed from ha_state_t
- handle_request_vote(): restore same-candidate idempotent re-grant —
deny only a DIFFERENT candidate in the same term, matching raft.c and
Raft §5.2 votedFor ∈ {Nil, candidateId} (bug-338)
- raft_init(): restore voted_for_term alongside a persisted vote; leaving
it 0 allowed a double vote in the same term across a restart (bug-339)
- myapp_run(): leader_known check treats a vote recorded under this node's
own name as a self-vote — production persists the real candidate name,
the "self" placeholder only appears in test mode
- raft_on_vote_request(): leader steps down on higher-term vote request
instead of denying it
Tests: test_proto_H6_restored_vote_blocks_second_vote added; H1 restore
assertion strengthened; test_ha_vote_gate.c driven through last_activity +
primary_ctrl_fd (the real production fields). Full /xce-build all green
(lib + controller + scheduler + Go suites, 0 failures, ASAN clean).
deploy-ha.sh: start.sh now forwards extra args to the controller binary.
- ha_state_t.n_peers now matches raft_config_t.n_peers convention:
total cluster size (including self), consistently across both layers
- ha_start_election_async: ha->n_peers = n_peers (candidates_count)
- Convergence/counting loops: i < n_peers - 1 (skip self for standby arrays)
- Single-node: n_peers=1, threshold=0 (same behavior, clear semantics)
- ha_elect_ctx_t.n_peers unchanged (separate field for vote array sizing)
- Tests: 3-node n_peers=2->3, single-node 0->1, loop bounds updated
E2E test 6.7: 3-node cluster lifecycle verified
- Initial: ctrl-1 PRIMARY via majority convergence, no degraded mode
- Kill primary: RDHUP detected on both standbys, ctrl-2 elected at term=4
- No data loss: config tag preserved across failover
- Full ASAN build green
6.3: Fix single-node bug — ha_compute_safe_committed_lsn now returns
self_lsn instead of 0 for n_peers=0 (prevents WAL truncation on
single-node re-election). Add self_lsn/self_tag to ha_elect_ctx_t,
populated unconditionally in ha_start_election_async. All 3 test
scenarios pass under ASAN.
6.4: Add test_snapshot_recv_128kb_two_chunks (128KB snapshot in
2x64KB chunks, verifies size and applied_lsn); 4 other test cases
already existed from tasks 3.5c/3.5d. All ASAN-clean.
- Change HA_DEFAULT_COMMITTING_TIMEOUT_MS from 10000 to 60000
- committing_timeout_fn: count converged/pending standbys from
standby_converged[], log WARN with counts, then promote (degraded mode)
- Replace hardcoded 10000 in test_ha_evaluate_committing.c with macro
- Three new tests: default=60000, degrade-promote with 1/2 and 0/2 converged
- Strip handle_ctrlhello: remove repl_add_standby, WAL streaming,
snapshot check, push_config_to_standbys, and CtrlHelloReply
- Keep only: set primary_ctrl_fd, call ha_on_heartbeat_received,
arm ha_arm_heartbeat_timeout_vtask, log INFO
- All replication decisions now handled by heartbeat decision loop
- Test: call with NULL repl + config_tag mismatch → no crash, no repl
messages enqueued, primary_ctrl_fd set correctly
- In raft_cb_become_leader, after persist_truncate_wal_above(safe_lsn),
store safe_lsn to ha->last_known_committed_lsn via atomic release
- Test: 3-node voters [100,150,200] → safe_lsn=150; asserts
ha->last_known_committed_lsn == 150 after raft_cb_become_leader_for_test
