RE: Enhance traceability of wal_level changes for backup management

On Friday, March 12, 2021 5:04 PM Peter Eisentraut <peter(dot)eisentraut(at)enterprisedb(dot)com> wrote:
> On 08.03.21 03:45, osumi(dot)takamichi(at)fujitsu(dot)com wrote:
> > OK. The basic idea is to enable backup management tools to recognize
> > wal_level drop between*snapshots*.
> > When you have a snapshot of the cluster at one time and another one at
> > different time, with this new parameter, you can see if anything that
> > causes discontinuity from the drop happens in the middle of the two
> > snapshots without efforts to have a look at the WALs in between.
>
> Is this an actual problem? Changing wal_level requires a restart. Are users
> frequently restarting their servers to change wal_level and then wonder why
> their backups are misbehaving or incomplete? Why? Just like fsync is
> "breaks your database", wal_level might as well be "breaks your backups". Is
> it not documented well enough?
I understand what you mean.
However, this thread partly came from a concern of
another thread to introduce a new wal_level
which would make the wal_level change like above more common.
Therefore, I think it's preferable to discuss better safeguard or
better notification way to users instead of just leaving it without doing anything.

Best Regards,
Takamichi Osumi