Re: pgstat_send_connstats() introduces unnecessary timestamp and UDP overhead

At Wed, 25 Aug 2021 13:21:52 +0900 (JST), Kyotaro Horiguchi <horikyota.ntt@gmail.com> wrote in 
> At Wed, 25 Aug 2021 12:51:58 +0900, Michael Paquier <michael@paquier.xyz> wrote in 
> > - Throttle the frequency where the connection stat packages are sent,
> > as of [2].
> > 
> > Magnus, this open item is assigned to you as the committer of
> > 960869d.  Could you comment on those issues?
> > 
> > [1]: https://www.postgresql.org/message-id/4095ceb328780d1bdba77ac6d9785fd7577ed047.camel@cybertec.at
> > [2]: https://www.postgresql.org/message-id/20210801205501.nyxzxoelqoo4x2qc@alap3.anarazel.de
> 
> About [2], we need to maintain session active/idel times on additional
> menbers in backend status.  Letting gpgstat_report_activity to
> directly scribble on backend status array would work?

So the attached is roughly that (just a PoC, of course).

- accumulate active and idle time on backend status array.
  (pgstat_report_activity)

- pgstat_get_db_session_time() and friends read pgstat file then sum
  up relevant members in backend status array. (So it scans on the
  array for every number of every database X().

- The function pgstat_send_connstats is called only at the end of a
  connection.  It reads backend status element then send the numbers
  to stats collector.  pgstat_shutdown_hook needs to be moved from
  on_shmem_exit to before_shmem_exit to read MyBEEntry.

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center