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).
Implements sync replication wait: primary blocks until at least one non-catching-up
standby ACKs the target LSN, or times out. Uses pthread_cond_timedwait with
CLOCK_REALTIME deadline. Inner loop rechecks all standbys after each wakeup to
guard against spurious wakeups.
ACK deadlock prevention: repl_on_ack() is called exclusively from the io_worker
read callback (not vtaskmgr), so it only does atomic_store + pthread_cond_signal —
safe to call while vcpu threads block in repl_wait_ack().
4 new TDD tests (all green, 9 total in test_repl_unit):
- test_wait_ack_no_standbys_returns_enodev
- test_wait_ack_already_acked
- test_wait_ack_timeout (verifies >=80ms elapsed)
- test_wait_ack_woken_by_background_ack (pthread thread signals after 30ms)
Add replicator_t structure with per-standby connection slots (standby_conn_t),
lifecycle (repl_init/repl_fini), slot management (repl_add_standby,
repl_remove_standby, repl_expire_disconnect_slots), ACK tracking
(repl_on_ack), WAL trim guard (repl_trim_lsn), and stubs for
repl_broadcast/repl_wait_ack (wired in P2-3/P2-4).
Uses mylock_t (pthread_mutex_t alias) with mylock_lock/mylock_unlock.
snap_interval_s==0 in repl_expire_disconnect_slots forces immediate expiry
to support deterministic unit testing.
5 new Unity tests all pass; 115 pre-existing controller tests unchanged.
