Re: Writing WAL files

On Sun, 4 Oct 2020 at 20:52, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:

>
> This is on purpose; archiving WAL files that contain nothing is pure
> wastage of good electrons.

Seriously? Oh, holy ****

> I suggest that in PG12 you can monitor the
> "lag" of a standby server more directly by looking at columns write_lag,
> flush_lag, replay_lag in the pg_stat_replication view.

And are those things updated when there are no changes to the master
database?
If so, can anyone make the case that continually checking and updating them
(how often?) wastes fewer electrons than shipping an empty file every few
minutes?

Or are they only measured when something is updated?

If I upgrade/install/reconfigure/restart something, I want to know that I
haven't broken the sync.

Will looking at the replay_lag (where? master? standby?) tell me that the
sync is still good?
Or will they capture the last sync. operation, and so only tell me what I
need to know if I do some kind of database operation?

And if I have to do some kind of database operation, I may as well stick
wiht the current arrangement,
since that operation would force a WAL file transfer anyway...

(You'll need to
> change your configuration so that it uses streaming replication instead
> of pg_standby and rsync, but that's far more convenient so it's a good
> change anyway.)
>

Maybe, but it's forcing me to spend time understanding stuff that I really
don't want to know about.

Robert.

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