Re: Walsender may fail to send wal to the end.

On Fri, Mar 26, 2021 at 10:16:40AM -0700, Andres Freund wrote:
> Hi,
>
> On 2021-03-26 18:20:14 +0900, Kyotaro Horiguchi wrote:
> > This is because XLogSendPhysical detects removal of the wal segment
> > currently reading by shutdown checkpoint. However, there' no fear of
> > overwriting of WAL segments at the time.
> >
> > So I think we can omit the call to CheckXLogRemoved() while
> > MyWalSnd->state is WALSNDSTTE_STOPPING because the state comes after
> > the shutdown checkpoint completes.
> >
> > Of course that doesn't help if walsender was running two segments
> > behind. There still could be a small window for the failure. But it's
> > a great help to save the case of just 1 segment behind.
>
> -1. This seems like a bandaid to make a broken configuration work a tiny
> bit better, without actually being meaningfully better.

Agreed. Still, wouldn't it be better to avoid such configurations and
protect a bit things with a check on the new value?
--
Michael