On Fri, Dec 08, 2023 at 04:58:52PM +0100, Juergen Gross wrote: > On 08.12.23 16:46, Andrew Cooper wrote: > > On 21/11/2023 11:40 am, Juergen Gross wrote: > > > The "-N" (do not daemonize) command line option is of questionable use: > > > its sole purpose seems to be to aid debugging of xenstored by making it > > > easier to start xenstored under gdb, or to see any debug messages > > > easily. > > > > > > Debug messages can as well be sent to syslog(), while gdb can be > > > attached to the daemon easily. The only not covered case is an error > > > while initializing xenstored, but this could be handled e.g. by saving > > > a core dump, which can be analyzed later. > > > > > > The call of talloc_enable_leak_report_full() done only with "-N" > > > specified is no longer needed, as the same can be achieved via > > > "xenstore-control memreport". > > > > > > Signed-off-by: Juergen Gross <jgr...@suse.com> > > > > Systemd wants daemons to not fork, because systemd can start them up in > > a better-prescribed environment than deamonise() can make. > > > > It was a lazy port to system which has caused us not to be using -N in > > the first place. > > > > So no - I think this option specifically wants to stay, and the systemd > > integration improved. > > The problem with this approach is that we have some functionality in the > launch-xenstore script relying on [o]xenstored coming back after having > forked off the daemon: we are setting the oom-score, which can be done
It's perfectly reasonable to bane the use of "-N" when using `./launch-xenstore` to start xenstored. It doesn't mean that the option needs to be removed from xenstored. > only when knowing the process id. > > So we need a solution for this problem before we can really encourage > users to use the -N option. > > Please note that setting the oom-score from within xenstored was rejected > back when I posted a patch in this regard, especially as it is specific to > Linux. Additionally this would mean we need to add this functionality to > xenstored AND oxenstored. There's still a world where -N can be used, and oom-score can be set, I'm pretty sure that can be done with an hand-crafted "systemd.service" file. One probably need to have something like "OOMPolicy=" or "OOMScoreAdjust=" in their service file, and start the `xenstored` daemon of their choice directly, even with -N as systemd can detect when the daemon is ready because we use sd_notify() (at least in cxenstored). So, I think we should keep -N. Cheers, -- Anthony PERARD
