Re: prevent immature WAL streaming

On 2021-Sep-24, Hannu Krosing wrote:

Hi Hannu

> In the first email you write
>
> > As mentioned in the course of thread [1], we're missing a fix for
> streaming replication to avoid sending records that the primary hasn't
> fully flushed yet. This patch is a first attempt at fixing that problem
> by retreating the LSN reported as FlushPtr whenever a segment is
> registered, based on the understanding that if no registration exists
> then the LogwrtResult.Flush pointer can be taken at face value; but if a
> registration exists, then we have to stream only till the start LSN of
> that registered entry.
>
> So did we end up holding back the wal_sender to not send anything that
> is not confirmed as flushed on master

No. We eventually realized that that approach was a dead end, so I
abandoned the whole thing and attacked the problem differently. So your
other questions don't apply. I tried to make the commit message explain
both the problem and the solution in as much detail as possible; please
have a look at that and let me know if something is unclear.

Thanks

--
Álvaro Herrera PostgreSQL Developer — https://www.EnterpriseDB.com/
"El miedo atento y previsor es la madre de la seguridad" (E. Burke)