Re: trying again to get incremental backup

On Thu, Nov 16, 2023 at 12:34 PM Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
> Putting those two thoughts together, I think pg_basebackup with
> --progress could tell you "still waiting for the summary file up to LSN
> %X/%X to appear, and the walsummarizer is currently handling lsn %X/%X"
> or something like that. This would probably require two concurrent
> connections, one to run BASE_BACKUP and another to inquire server state;
> but this should easy enough to integrate together with parallel
> basebackup later.

I had similar thoughts, except I was thinking it would be better to
have the warnings be generated on the server side. That would save the
need for a second libpq connection, which would be good, because I
think adding that would result in a pretty large increase in
complexity and some not-so-great user-visible consequences. In fact,
my latest thought is to just remove the timeout altogether, and emit
warnings like this:

WARNING: still waiting for WAL summarization to reach %X/%X after %d
seconds, currently at %X/%X

We could emit that every 30 seconds or so until either the situation
resolves itself or the user hits ^C. I think that would be good enough
here. If we want, the interval between messages can be a GUC, but I
don't know how much real need there will be to tailor that.

--
Robert Haas
EDB: http://www.enterprisedb.com