Re: Tracking wait event for latches

On Tue, Sep 20, 2016 at 7:13 PM, Thomas Munro
<thomas(dot)munro(at)enterprisedb(dot)com> wrote:
> This paragraph seems a bit confused. I suggest something more like
> this: "The server process is waiting for one or more sockets, a timer
> or an interprocess latch. The wait happens in a WaitEventSet,
> <productname>PostgreSQL</>'s portable IO multiplexing abstraction."

I'm worried we're exposing an awful lot of internal detail here.
Moreover, it's pretty confusing that we have this general concept of
wait events in pg_stat_activity, and then here the specific type of
wait event we're waiting for is the ... wait event kind. Uh, what?

I have to admit that I like the individual event names quite a bit,
and I think the detail will be useful to users. But I wonder if
there's a better way to describe the class of events that we're
talking about that's not so dependent on internal data structures.
Maybe we could divide these waits into a couple of categories - e.g.
"Socket", "Timeout", "Process" - and then divide these detailed wait
events among those classes.

The "SecureRead" and "SecureWrite" wait events are going to be
confusing, because the connection isn't necessarily secure. I think
those should be called "ClientRead" and "ClientWrite".
Comprehensibility is more important than absolute consistency with the
C function names.

Another thing to think about is that there's no way to actually see
wait event information for a number of the processes which this patch
instruments, because they don't appear in pg_stat_activity.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company