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fix(ha): close permanent catch-up wedge from duplicated replication-target formula (bug-1478)

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Two independent call sites duplicated target = max(committed_lsn,
last_written): ha.c's heartbeat/stateReport dispatch (repl_ack_decode_and_
dispatch) and config_repl.c's catchup_derive_target (used by the ACK-driven
catch-up continuation path). Once config-upgrade-snapshot's marker-triggered
checkpoint advances last_written one LSN past an already-committed
committed_lsn (the checkpoint's own consumed, never-replicated LSN slot),
the unconditional max() permanently wedges every standby's catch-up target
at an unreachable value -- the primary re-streams an empty range every
heartbeat forever.

Extracted the shared, pure ha_compute_repl_target_lsn(committed_lsn,
last_written) (ha.h/ha.c), which only falls back to last_written on genuine
committed_lsn==0 bootstrap, and pointed both call sites at it so they can
never disagree again.

Fixing the second call site exposed three pre-existing tests in
test_convergence_verification.c that hardcoded the old buggy formula's
output as their expected target; updated their fixture values (committed_lsn
4->9, matching appended_lsn) to decouple them from the now-fixed edge case,
which already has dedicated pure-function coverage in test_ha_role.c.

GREEN: full controller_unit_test suite = 1040 tests, 0 failures, clean
across multiple runs. Live-verified via run-ha-soak.sh
--config-upgrade-wal-trim (18 jobs, zero job loss, ctrl-1 reconverged 3-of-3
using the preserved floor segment) -- unblocks config-upgrade-snapshot
task 8.9.
This commit is contained in:
Rongsong Shen 2026-07-28 09:53:20 +00:00
parent 71223ec712
commit 102e263cce
9 changed files with 850 additions and 20 deletions
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12
src/controller/config_repl.c
View file

@ -2612,8 +2612,14 @@ static int repl_ep_still_registered(replicator_t *r, repl_ep_t ep)
return found;
}
/* re-derive the replication target exactly as ha.c:2771-2776 / D6:
* target = max(committed_lsn, last_written), last_written = current_lsn - 1. */
/* re-derive the replication target via the SAME pure function
* repl_ack_decode_and_dispatch (ha.c) uses, so this continuation path and
* the heartbeat decision path can never disagree on what a standby must
* catch up to (bug-1478: this function used to duplicate the raw
* max(committed_lsn, last_written) formula inline, independently of the
* ha.c call site the fix landed in — a local-only, never-replicated
* WAL_CHECKPOINT trailing an already-advancing committed_lsn permanently
* wedged catch-up here as well, via the exact same mechanism). */
static uint64_t catchup_derive_target(cluster_t *c)
{
uint64_t committed = atomic_load_explicit(&c->persist.committed_lsn,
@ -2623,7 +2629,7 @@ static uint64_t catchup_derive_target(cluster_t *c)
? c->persist.current_lsn - 1
: 0;
pthread_mutex_unlock(&c->persist.lock);
return last_written > committed ? last_written : committed;
return ha_compute_repl_target_lsn(committed, last_written);
}
/* Invoke the catch-up streaming path for [standby_lsn+1, target]. Mirrors the