Re: BUG #17928: Standby fails to decode WAL on termination of primary

At Sun, 16 Jul 2023 17:49:05 -0700, Noah Misch <noah(at)leadboat(dot)com> wrote in
> On Tue, Jul 11, 2023 at 03:54:14PM +0900, Kyotaro Horiguchi wrote:
> > I like the patch for its code clean up, but I'm afraid that it removes
> > the existing record length check when reading continued
> > pages.
>
> The removed check would be repetitive in all cases known to me, but I wouldn't
> mind keeping the check instead.

Ah. I got it. No need to do that again.

> > I believe reading the whole header is the most sensible approach as it
> > can prevent unnecessary memory requests. Another potential solution
> > (or hack) for this specific case is to let XLogWalRcvFlush write a
> > finalizing ((uint32)0) when dying is true. This stabilizes the
> > behavior to "invalid record length.. got 0" when running the TAP test.
...
> That's inexpensive in cycles, and it should make the failures in question
> quite rare. If we do that instead of pre-zeroing, I think we'd still want to
> be ready for invalid lengths, for the case of unclean standby shutdown.

Agreed.

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center