Hi, On Tue, May 19, 2026 at 1:00 PM Alexander Lakhin <[email protected]> wrote: > > Hello Alexander and Xuneng, > > 06.04.2026 22:49, Alexander Korotkov wrote: > > Thank you, I've pushed your version of patchset. I made two minor > corrections for patch #2: mention default mode value in the header > comment, and fallback to polling on has_wal_read_bug sparc64+ext4 bug. > > > I discovered a new test failure, that is apparently caused by new > wait_for_catchup() implementation [1]: > [06:20:23.110](1.069s) not ok 8 - check that the slot state changes to > "extended" > [06:20:23.110](0.001s) # Failed test 'check that the slot state changes to > "extended"' > # at > /Users/ec2-user/bf/goldfish/HEAD/pgsql/src/test/recovery/t/019_replslot_limit.pl > line 140. > [06:20:23.111](0.000s) # got: 'unreserved' > # expected: 'extended' > [06:20:23.231](0.120s) not ok 9 - check that the slot state changes to > "unreserved" > [06:20:23.231](0.000s) # Failed test 'check that the slot state changes to > "unreserved"' > # at > /Users/ec2-user/bf/goldfish/HEAD/pgsql/src/test/recovery/t/019_replslot_limit.pl > line 152. > [06:20:23.231](0.000s) # got: 'lost|' > # expected: 'unreserved|t' > > I've managed to reproduce such failures with: > diff --git a/src/backend/replication/walreceiver.c > b/src/backend/replication/walreceiver.c > index 07eac07b9ce..493ce92674e 100644 > --- a/src/backend/replication/walreceiver.c > +++ b/src/backend/replication/walreceiver.c > @@ -1143,2 +1143,3 @@ XLogWalRcvSendReply(bool force, bool requestReply, bool > checkApply) > > +pg_usleep(10000); > /* Get current timestamp. */ > diff --git a/src/backend/replication/walsender.c > b/src/backend/replication/walsender.c > index 04aa770d981..19cda3a6b51 100644 > --- a/src/backend/replication/walsender.c > +++ b/src/backend/replication/walsender.c > @@ -2521,2 +2521,3 @@ ProcessStandbyReplyMessage(void) > > +pg_usleep(100000); > /* the caller already consumed the msgtype byte */ > > Concretely, a loop: > for i in {1..100}; do echo "ITERATION $i"; PROVE_TESTS="t/019*" make -s check > -C src/test/recovery/ || break; done > failed for me on iterations 2, 1, 7: > ITERATION 7 > # +++ tap check in src/test/recovery +++ > t/019_replslot_limit.pl .. 8/? > # Failed test 'check that the slot state changes to "extended"' > # at t/019_replslot_limit.pl line 140. > # got: 'unreserved' > # expected: 'extended' > t/019_replslot_limit.pl .. 26/? # Looks like you failed 1 test of 26. > t/019_replslot_limit.pl .. Dubious, test returned 1 (wstat 256, 0x100) > Failed 1/26 subtests > > With "WAIT FOR LSN" in wait_for_catchup() disabled, 100 iterations > passed. > > Having extra logging added, I could see the key difference. > Failed run: > 2026-05-19 22:01:37.968 EEST client backend[3632148] 019_replslot_limit.pl > LOG: !!!GetWALAvailability| targetLSN: 0/016C0000, targetSeg: 22, > oldestSlotSeg: 23, oldestSegMaxWalSize: 24, oldestSeg: 22 > 2026-05-19 22:01:37.968 EEST client backend[3632148] 019_replslot_limit.pl > STATEMENT: SELECT wal_status FROM pg_replication_slots WHERE slot_name = > 'rep1' > vs > Successful run: > 2026-05-19 22:04:18.102 EEST client backend[3633761] 019_replslot_limit.pl > LOG: !!!GetWALAvailability| targetLSN: 0/01700000, targetSeg: 23, > oldestSlotSeg: 23, oldestSegMaxWalSize: 24, oldestSeg: 23 > 2026-05-19 22:04:18.102 EEST client backend[3633761] 019_replslot_limit.pl > STATEMENT: SELECT wal_status FROM pg_replication_slots WHERE slot_name = > 'rep1' > > That is, with WAIT FOR LSN, primary in this test may advance > slot->data.restart_lsn to the expected position after wait_for_catchup() > returns. > > [1] > https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=goldfish&dt=2026-05-13%2006%3A15%3A03
Thanks for reporting this issue. I think this is related to the semantic change made earlier: wait_for_catchup() now returns once the standby itself has reached the target LSN, rather than waiting until the primary observes that position via pg_stat_replication. As a result, the primary may not yet have processed the standby feedback needed to advance the slot's restart_lsn when wait_for_catchup() returns. Actually, I was aware of this semantic change and previously thought it might be harmless. But this failure appears to disprove that. I'll prepare a patch to fix this shortly. -- Regards, Xuneng Zhou HighGo Software Co., Ltd.
