Re: Latches, signals, and waiting

On 15/09/10 16:55, Tom Lane wrote:
> So I'm wondering if we couldn't eliminate the five-second sleep
> requirement here too. It's problematic anyhow, since somebody looking
> for energy efficiency will still feel it's too short, while somebody
> concerned about fast failover will feel it's too long.

Yep.

> Could the
> standby triggering protocol be modified so that it involves sending a
> signal, not just creating a file?

Seems reasonable, at least if we still provide an option for more
frequent polling and no need to send signal.

> (One issue is that it's not clear what that'd translate to on Windows.)

pg_ctl failover ? At the moment, the location of the trigger file is
configurable, but if we accept a constant location like
"$PGDATA/failover" pg_ctl could do the whole thing, create the file and
send signal. pg_ctl on Window already knows how to send the "signal" via
the named pipe signal emulation.

Fujii-san suggested that we might have a user-defined function for
triggering failover as well. That's also handy, but it's not a
replacement because it only works in hot standby mode.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com