Re: Switching XLog source from archive to streaming when primary available

On Fri, Sep 9, 2022 at 10:57 AM Kyotaro Horiguchi
<horikyota(dot)ntt(at)gmail(dot)com> wrote:
>
> At Thu, 8 Sep 2022 10:53:56 -0700, Nathan Bossart <nathandbossart(at)gmail(dot)com> wrote in
> > On Thu, Sep 08, 2022 at 05:16:53PM +0530, Bharath Rupireddy wrote:
> > > I'm attaching the v3 patch with the review comments addressed, please
> > > review it further.
> >
> > My general point is that we should probably offer some basic preventative
> > measure against flipping back and forth between streaming and archive
> > recovery while making zero progress. As I noted, maybe that's as simple as
> > having WaitForWALToBecomeAvailable() attempt to restore a file from archive
> > at least once before the new parameter forces us to switch to streaming
> > replication. There might be other ways to handle this.
>
> +1.

Hm. In that case, I think we can get rid of timeout based switching
mechanism and have this behaviour - the standby can attempt to switch
to streaming mode from archive, say, after fetching 1, 2 or a
configurable number of WAL files. In fact, this is the original idea
proposed by Satya in this thread.

If okay, I can code on that. Thoughts?

--
Bharath Rupireddy
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com