Bug#955483: Alphanumeric ordering of depending sockets breaks restart

[Guido Günther]

Hi,
On Thu, Apr 02, 2020 at 12:45:00PM +0200, Christian Ehrhardt wrote:
> On Thu, Apr 2, 2020 at 10:54 AM Michael Biebl <biebl at debian.org> wrote:
> >
> > I don't think this is going to work.
> >
> > You'll need to restart both the service and socket in the correct order,
> 
> @Michael:
> I have tried "systemctl restart service socket socket" before and it works.
> But I was wondering if it might work just by accident, due to the service being
> not yet fully up when the sockets restart. And I was unsure if this
> could be racy.
> Are you saying this is "the right order" and this way around systemd
> will take care
> that service and sockets won't collide in a bad way?
> 
> > i.e.
> >
> > systemctl restart libvirtd.service libvirtd.socket
> >
> 
> In that case - as initially suggested when I filed against debhelper -
> at least the
> ordering of dh_installsystemd would need to ensure that it does not order
> everything alphabetically but instead start with the service followed by all th
> rest it picks up.
> 
> Today:
> $ grep Also /lib/systemd/system/libvirtd.service
> Also=virtlockd.socket
> Also=virtlogd.socket
> Also=libvirtd.socket
> Also=libvirtd-ro.socket
> 
> And due to that
> 
>    dh_installsystemd -p libvirt-daemon-system --restart-after-upgrade
> libvirtd.service
> 
> Gets generated into postinst as:
> 
> deb-systemd-invoke $_dh_action 'libvirtd-ro.socket' 'libvirtd.service'
> 'libvirtd.socket' 'virtlockd.socket' 'virtlogd.socket'
> 
> Triggering exactly that issue that we discuss here.
> 
> If it would generate the following it would work (I tried)
> deb-systemd-invoke $_dh_action 'libvirtd.service' 'libvirtd-ro.socket'
> 'libvirtd.socket' 'virtlockd.socket' 'virtlogd.socket'
> 
> @Michael:
> - would you agree that due to the issues in discussion
> dh_installsystem should change the order to always start with the
> service?
> 

See 955542 , we can't get the order right with the current Also= parsing
it seems. I'm also not sure if it's correct that Also= units are being
restarted as well.
Cheers,
 -- Guido