Two distinct HA livelocks, both verified on a live 3-node ASAN deploy
(kill+restart of primary and standby, plus SIGSTOP wedge injection).
bug-339 — election freshness-floor asymmetry (RDHUP failover path):
After the primary dies the two survivors could never elect a leader — both
only ever became follower while terms climbed in lockstep. The RDHUP candidate
advertised c->persist.committed_lsn, which a standby never advances (only the
primary commit engine writes it), while every voter computed its freshness floor
from max(applied_lsn, last_known_committed_lsn). So each survivor advertised a
stale-low LSN against a high voter floor and the freshness gate denied on both
sides. Fix: compute the candidate LSN via ha_vote_self_freshness so the
advertised value equals the voter floor (ha_on_primary_ctrl_fd_rdhup); also route
the boot-path election (myapp_run) through the same helper for symmetry.
bug-340 — wedged standby endpoint suppressed reconnect (rejoin path):
A killed/restarted peer's outbound endpoint on the primary could wedge (epoll
re-arm ENOENT) yet stay in standby_endpoints, so primary_heartbeat_fn's reconnect
scan treated the peer as still-connected and never re-established a ctrlhello
channel — the restarted node never heard from the primary and re-elected every
heartbeat_timeout (term climbing unbounded). xce_nop_req returns success on
enqueue even when the send can't progress, so the heartbeat layer never noticed.
Fix: primary_heartbeat_fn now evicts a standby that was responsive once
(ts_last_in > 0) but has been silent past heartbeat_timeout — symmetric with the
standby's own liveness poll — and the reconnect scan re-establishes the channel.
Uses existing endpoint_t.ts_last_in (no libnetio change).
Tests (RED->GREEN):
- test_ha_rdhup_integration: candidate advertises freshness floor, not stale committed_lsn
- test_ha_liveness: evicts_silent_standby + keeps_live/keeps_unconfirmed (no false eviction)
Verification task: confirmed config_repl.c handle_ctrlhello calls both
ha_on_heartbeat_received and ha_arm_heartbeat_timeout_vtask (delaymgr poll).
Confirmed ha_on_primary_ctrl_fd_rdhup leads with ha_disarm (Req 5.4).
No pthread_create in heartbeat arm path (Req 1.6). Add thread-count test.
Extend primary_heartbeat_fn to read last_push_time per standby and send NOP
only when elapsed >= heartbeat_interval_s. on_standby_connected writes
last_push_time before ctrlhello send. Remove workaround xce_nop_req at end
of on_standby_connected. Add ha_nop_req_hook XCE_TESTING seam. 3 new tests.
Remove hb_vtask_t, hb_timeout_thread, s_hb_vtask from ha.c. Replace with
liveness_poll_ctx_t + delaymgr liveness_poll_fn: checks cancelled flag and
role==CTRL_STANDBY before acting; re-arms at heartbeat_interval_ms/2.
ha_on_primary_ctrl_fd_rdhup calls ha_disarm_heartbeat_timeout_vtask first
to prevent duplicate failover (Req 5.4). ha_on_heartbeat_received writes
last_activity via clock_gettime. Add test_ha_liveness.c with 7 unit tests.
