Re: Stale description for pg_basebackup

At Tue, 20 Apr 2021 13:32:35 +0900 (JST), Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> wrote in
> Hello.
>
> It seems to me that there's a stale description in the documentation
> of pg_basebackup.
>
> https://www.postgresql.org/docs/13/app-pgbasebackup.html
>
> > Note that there are some limitations in taking a backup from a standby:
> ...
> > If you are using -X none, there is no guarantee that all WAL files
> > required for the backup are archived at the end of backup.
>
> Actually, pg_basebackup waits for the all required files to be
> archived, which is an established behavior by commit
> 52f8a59dd9(at)PG10(dot) However, the same commit seems to have forgot to
> change the doc for pg_basebackup. (The current description is
> introduced by 9a4d51077c(at)PG10)
>
> The attached is a proposal to rewrite it as the following.
>
> + If you are using -X none, pg_basebackup may wait for a long time for
> + all the required WAL files to be archived. In that case, You may need
> + to call pg_switch_wal() on the primary to complete it sooner.

I forgot to preserve the description about *primary*. It should be as
the following instead.

+ If you are using -X none, there is no guarantee on the primary that
+ all WAL files required for the backup are archived at the end of
+ backup. When the standby is configured as archive_mode=always,
+ pg_basebackup may wait for a long time for all the required WAL files
+ to be archived. In that case, You may need to call pg_switch_wal() on
+ the primary to complete it sooner.

Attached.

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center