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commit    bbbc0888b356af7687fc917e7835701a75955503
Author:   Fujii Masao <fujii@postgresql.org>
Date:     Fri Mar 06 07:43:40 2026 +0000
First released in: 14.23, 15.18, 16.14, 17.10, 18.4

    Fix publisher shutdown hang caused by logical walsender busy loop.
    
    Previously, when logical replication was running, shutting down
    the publisher could cause the logical walsender to enter a busy loop
    and prevent the publisher from completing shutdown.
    
    During shutdown, the logical walsender waits for all pending WAL
    to be written out. However, some WAL records could remain unflushed,
    causing the walsender to wait indefinitely.
    
    The issue occurred because the walsender used XLogBackgroundFlush() to
    flush pending WAL. This function does not guarantee that all WAL is written.
    For example, WAL generated by a transaction without an assigned
    transaction ID that aborts might not be flushed.
    
    This commit fixes the bug by making the logical walsender call XLogFlush()
    instead, ensuring that all pending WAL is written and preventing
    the busy loop during shutdown.
    
    Backpatch to all supported versions.
    
    Author: Anthonin Bonnefoy <anthonin.bonnefoy@datadoghq.com>
    Reviewed-by: Alexander Lakhin <exclusion@gmail.com>
    Reviewed-by: Fujii Masao <masao.fujii@gmail.com>
    Discussion: https://postgr.es/m/CAO6_Xqo3co3BuUVEVzkaBVw9LidBgeeQ_2hfxeLMQcXwovB3GQ@mail.gmail.com
    Backpatch-through: 14


 src/backend/replication/walsender.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 1c10a7793df..6480ef5a11d 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -1882,8 +1882,8 @@ WalSndWaitForWal(XLogRecPtr loc)
 		 * otherwise we'd possibly end up waiting for WAL that never gets
 		 * written, because walwriter has shut down already.
 		 */
-		if (got_STOPPING)
-			XLogBackgroundFlush();
+		if (got_STOPPING && !RecoveryInProgress())
+			XLogFlush(GetXLogInsertRecPtr());
 
 		/*
 		 * To avoid the scenario where standbys need to catch up to a newer


[parent: 8b198b093fd2]