Re: exposing wait events for non-backends (was: Tracking wait event for latches)

On Fri, Mar 10, 2017 at 3:11 AM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> On 2017-03-09 16:37:29 -0500, Tom Lane wrote:
>> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> > On Thu, Mar 9, 2017 at 2:30 PM, Peter Eisentraut
>> > <peter(dot)eisentraut(at)2ndquadrant(dot)com> wrote:
>> >> In practice, I think it's common to do a quick select * from
>> >> pg_stat_activity to determine whether a database instance is in use.
>>
>> > I thought of the same kind of thing, and it was discussed upthread.
>> > There seemed to be more votes for keeping it all in one view, but that
>> > could change if more people vote.
>>
>> I've not been paying much attention to this thread, but it seems like
>> something that would help Peter's use-case and have other uses as well
>> is a new column that distinguishes different process types --- user
>> session, background worker, autovacuum worker, etc.
>
> The patches upthread add precisely such a column.
>
The patch exposes auxiliary processes, autovacuum launcher and
bgworker along with other backends in pg_stat_activity. It also adds
an extra column, named proc_type (suggested by Craig
and Robert), to indicate the type of process in pg_stat_activity view.
proc_type includes:

* client backend
* autovacuum launcher
* wal sender
* bgworker
* writer
* checkpointer
* wal writer
* wal receiver

Here is the present output with the relevant columns.
postgres=# SELECT wait_event_type, wait_event, state, proc_type FROM
pg_stat_activity;
wait_event_type | wait_event | state | proc_type
-----------------+---------------------+--------+---------------------
Activity | AutoVacuumMain | idle | autovacuum launcher
Activity | LogicalLauncherMain | idle | bgworker
Activity | WalSenderMain | idle | wal sender
| | active | client backend
Activity | BgWriterMain | idle | writer
Activity | CheckpointerMain | idle | checkpointer
Activity | WalWriterMain | idle | wal writer
(7 rows)

--
Thanks & Regards,
Kuntal Ghosh
EnterpriseDB: http://www.enterprisedb.com