[Xen-devel] making xenstore domain easy configurable

[Juergen Gross <jgross@xxxxxxxx>]

I'm just writing some patches to make it easy to switch between
xenstore daemon and xenstore domain. My plan is to achieve this
by a global configuration file containing configuration options
for the host (e.g. /etc/xen/xen.conf).

With the current systemd support this is not easy. There are
systemd socket definitions to let systemd create the sockets for
xenstored. As the sockets are not to be created in case xenstore
is running in a xenstore domain things are becoming complicated.

Today we have the following xenstore related systemd items:

- xenstored_ro.socket and xenstored.socket
- xenstored.service depending on the sockets
- other services depending on xenstored.service

A xenstore domain would need:

- xenstore-domain.service
- other services depending on xenstore-domain.service

Being able to switch between both schemes just via a config file
seems to be not easy, at least I don't know of any way to do the
socket creation only in case they are required without breaking
the dependency chain.

So I'd suggest to remove xenstored_ro.socket and xenstored.socket
and let xenstored create the sockets (as it is doing without
systemd). I'm not aware of any disadvantage, as xenstored isn't
restartable and thus can't take advantage of the permanent sockets
offered by systemd.

This would mean I could rip out the systemd specific stuff from
xenstored and oxenstored. I could create a single xenstore.service
script evaluating the config file and starting the correct xenstore
(xenstored or xenstore domain). The other services would then depend
on xenstore.service. This would remove the need to specify the
type of xenstore daemon/domain (ocaml based or C based) in the systemd
file, too.

Is there a better way to achieve what I want? Any other opinions?


Juergen

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