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.
Implement the catch-up state machine as testable pure-logic functions:
- repl_start_catchup(): marks standby in_catch_up=1, stores join_applied_lsn
- repl_complete_catchup(): clears in_catch_up=0, broadcasts ack_cond so any
blocked repl_wait_ack() re-checks the ACK condition immediately
- repl_needs_snapshot(): pure predicate — returns 1 when standby LSN predates
oldest surviving WAL segment (snapshot transfer required), 0 otherwise
Also fixes pre-existing linker error: repl.c was missing from controller_src
(xce_controller production binary), causing undefined references to repl_*
symbols introduced in P2-4.
7 new TDD tests in test_repl_catchup.c — all pass. Existing tests green.
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.
