On Wed, Aug 27, 2014 at 11:18:11AM +0200, Umut Tezduyar Lindskog wrote: > On Wed, Aug 27, 2014 at 3:24 AM, Zbigniew Jędrzejewski-Szmek > <zbys...@in.waw.pl> wrote: > > On Tue, Aug 26, 2014 at 08:49:29PM -0400, Gary Mort wrote: > >> Socket based activation for systemd is a really cool feature for my > >> dev system. > >> > >> Prior to using socket based activation, on my dev system I would > >> have 2 choices: > >> > >> 1) Automatically start mysql, apache, php fastcgi, memcached, > >> mongodb and a dozen other services just in case I happen to be > >> working with them on this particular bootup. > >> > >> 2) Manually start them when needed....usually /after/ trying to test > >> something and discovering the service isn't running. > >> > >> With socket based activation, I can start up dozens of servers on > >> different sockets and they won't bog my system down - they only > >> truely activate if they are actually used. > >> > >> However, there is still a missing item to this feature[or it's not > >> missing and I am simply unaware of it] - there is no way to do the > >> reverse. IE if apache is running on my server there is no way to > >> configure things so if there are no active socket connections for 30 > >> minutes, have it automatically shutdown and pass the socket control > >> back. > > This has to be implemented in the service itself. After the service > > has been started systemd does not monitor the socket and simply > > does not know when the service can be safely stopped. In addition > > to the socket passed by systemd the service might have opened > > additional channels of communication itself, or might be doing > > some processing that systemd knows nothing about..., so only the > > service knows when it has idle and how long it has been idle. > > The service can close the socket and shut down. This is race free, > > because if a connection comes on the socket in the meantime, it will > > be queued by the kernel, and then when the service has shut down, > > systemd will start it again. > > > > Various systemd services like systemd-hostnamed do this kind of thing > > already. > > I really think this can be achieved with notify socket and the > advantage would be having a system wide stop on idle value. You mean that the daemons would notify systemd about activity and it would keep track when to stop them? I guess possible, but I think it would be still racy, unless the notification protol was synchronous or it was possible for the service to "deny" the stop request sent by systemd. All in all, I don't think the complexity is worth it, since it is very simple for an event-loop based the service to do on its own.
Zbyszek > Note: I always mixup StopWhenUnneeded=. The name makes me believe that.... > > Umut _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
