From 52c53fa9c2e7648565103aea82650964bff2385c Mon Sep 17 00:00:00 2001 From: Zhijie Hou Date: Thu, 9 Apr 2026 20:11:40 +0800 Subject: [PATCH v4] Fix slotsync worker busy loop causing repeated logical decoding logs. Previously, the slotsync worker could enter a busy loop and emit four logical log messages every 200 ms, even when both the primary and standby were idle. This happened because the worker incorrectly treated certain cases as successful slot updates, causing it to use the minimum sleep interval and repeatedly restart slot syncing. This commit fixes this by ensuring the worker does not treat such cases as updates, allowing it to sleep normally and avoid excessive log output. --- src/backend/replication/logical/slotsync.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/src/backend/replication/logical/slotsync.c b/src/backend/replication/logical/slotsync.c index f90653e5232..64db2e9fd8c 100644 --- a/src/backend/replication/logical/slotsync.c +++ b/src/backend/replication/logical/slotsync.c @@ -332,10 +332,15 @@ update_local_synced_slot(RemoteSlot *remote_slot, Oid remote_dbid) slot->data.confirmed_flush = remote_slot->confirmed_lsn; slot->data.catalog_xmin = remote_slot->catalog_xmin; SpinLockRelease(&slot->mutex); + + updated_xmin_or_lsn = true; } else { bool found_consistent_snapshot; + XLogRecPtr old_confirmed_lsn = slot->data.confirmed_flush; + XLogRecPtr old_restart_lsn = slot->data.restart_lsn; + XLogRecPtr old_catalog_xmin = slot->data.catalog_xmin; LogicalSlotAdvanceAndCheckSnapState(remote_slot->confirmed_lsn, &found_consistent_snapshot); @@ -365,9 +370,16 @@ update_local_synced_slot(RemoteSlot *remote_slot, Oid remote_dbid) skip_reason = SS_SKIP_NO_CONSISTENT_SNAPSHOT; } - } - updated_xmin_or_lsn = true; + /* + * It is possible that the slot's xmin or LSNs are not updated, + * when the synced slot has reached consistent snapshot state or + * cannot build one at all. + */ + updated_xmin_or_lsn = (old_confirmed_lsn != slot->data.confirmed_flush || + old_restart_lsn != slot->data.restart_lsn || + old_catalog_xmin != slot->data.catalog_xmin); + } } /* Update slot sync skip stats */ -- 2.31.1