[systemd-devel] Support for large applications

[Lennart Poettering]

On Fri, 19.02.16 12:49, Zbigniew Jędrzejewski-Szmek (zbyszek at in.waw.pl) wrote:

> On Fri, Feb 19, 2016 at 01:42:12PM +0100, Michal Sekletar wrote:
> > On Wed, Feb 17, 2016 at 1:35 PM, Avi Kivity <avi at scylladb.com> wrote:
> > 
> > > 3. watchdog during startup
> > >
> > > Sometimes we need to perform expensive operations during startup (log
> > > replay, rebuild from network replica) before we can start serving. Rather
> > > than configure a huge start timeout, I'd prefer to have the service report
> > > progress to systemd so that it knows that startup is still in progress.
> > >
> > 
> > Did you have a look at sd_notify (man 3 sd_notify)? Basically, you can
> > easily patch your service to report status to systemd and tell to
> > systemd exactly when it is ready to serve the clients. Thus you can
> > avoid hacks like huge start timeout you've mentioned.
> 
> I don't think that helps, unless the service "lies" to systemd and
> tells it has finished startup when it really hasn't (systemd would
> ignore watchdog notifications during startup, and would do nothing if
> they stopped coming, so the service has to tell systemd first that it
> has started successfully, for the watchdog to be effective). Doing
> that would fix this issue, but would have that systemd wouldn't know
> that the service is still starting and would for example start
> subsequent jobs.
> 
> I don't think there's a way around the issue short of allowing
> watchdog during startup. Databases which do long recovery are a bit
> special, most programs don't exhibit this kind of behaviour, but maybe
> this case is important enough to add support for it.

Yeah, see my other mail. I am open to optionally require watchog
notifications even during the start and stpo operations.

Lennart

-- 
Lennart Poettering, Red Hat