Horton

Re: Shutdown indefinitely stuck due to unflushed FPI_FOR_HINT record

Fujii Masao <masao.fujii@gmail.com>

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From: Fujii Masao <masao.fujii@gmail.com>
To: Anthonin Bonnefoy <anthonin.bonnefoy@datadoghq.com>
Cc: PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2026-02-26T16:19:46Z
Lists: pgsql-hackers 
> Shutdown may be indefinitely stuck under the following circumstances:

Thanks for reporting this issue and for the patch!

I was able to reproduce the problem on master.


On Tue, Feb 24, 2026 at 6:47 PM Anthonin Bonnefoy
<anthonin.bonnefoy@datadoghq.com> wrote:
> So, it looks like the root issue is more that the async LSN isn't
> updated when a transaction without xid is rollbacked.
> When going through CommitTransaction, such a transaction would still
> go through XLogSetAsyncXactLSN.
>
> I've updated the patch with this new approach: XLogSetAsyncXactLSN is
> now called in RecordTransactionAbort even when a xid wasn't assigned.
> With this, the logical walsender is able to force the flush of the
> last partial page using XLogBackgroundFlush.

I'm a bit concerned that this approach could cause walwriter to attempt
WAL writes more aggressively in some cases, adding overhead during
normal processing. If the goal is only to prevent shutdown from getting stuck,
instead, would it be sufficient for ShutdownXLOG() to call
XLogSetAsyncXactLSN() just before WalSndWaitStopping()?

Regards,

-- 
Fujii Masao

Commits

  1. Fix WAL flush LSN used by logical walsender during shutdown

  2. Use GetXLogInsertEndRecPtr in gistGetFakeLSN

  3. Fix publisher shutdown hang caused by logical walsender busy loop.