Re: Function to track shmem reinit time

On Tue, Apr 10, 2018 at 8:58 PM Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Tue, Apr 10, 2018 at 9:07 AM, David Steele <david(at)pgmasters(dot)net> wrote:
> > On 3/29/18 9:40 AM, Tomas Vondra wrote:
> >> On 03/28/2018 08:55 PM, David Steele wrote:
> >>> I'm setting this entry to Waiting on Author, but based on the discussion
> >>> I think it should be Returned with Feedback.
> >>
> >> Fine with me.
> >
> > This entry has been marked Returned with Feedback.
>
> I guess I'm in the minority here, but I don't see why it isn't useful
> to have something like this. It's a lot easier for a monitoring
> process to poll for this kind of thing than it is to monitor the logs.
> Not that log monitoring isn't a good idea, but this is pretty
> lightweight.

+1,

I think the issue this patch is addressing is that PostgreSQL now
doesn't have true uptime function. We now recommend using
pg_postmaster_start_time() for uptime calculation, but that isn't it.
When backed crashes, shmen is reinitialized and PostgreSQL is
restarted then uptime should be reset to zero, but
pg_postmaster_start_time() is not about that.

The major argument against this patch I got from the thread is that we
shouldn't introduce new functions exposing information, which could be
already fetched from logs. However, I think following this logic we
should remove pg_postmaster_start_time() too.

------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company