[systemd-devel] [IDEA] systemd as basis for HA clusters

[Lennart Poettering]

On Thu, 25.07.13 21:21, Tomasz Torcz (tomek at pipebreaker.pl) wrote:

> On Thu, Jul 25, 2013 at 06:51:21PM +0200, Lennart Poettering wrote:
> > On Fri, 19.07.13 21:05, Pablo Nehab Hess (pablo at hess.net.br) wrote:
> > 
> > > Hi all,
> > > 
> > > I was wondering how much systemd could add to current high
> > > availability cluster setups.
> > > 
> > > Today systemd is used on HA clusters as just an init replacement.
> > > However, there are systemd features that might come in handy and
> > > improve the overall performance and even reliability of such clusters:
> > > 
> > > * watchdog functionality as in
> > > <http://0pointer.de/blog/projects/watchdog.html> is the most evident
> > > feature;
> > > * tcp-based dbus communication could be used to exchange information
> > > between cluster members;
> > > 
> > > Also, I believe systemd functionality could be extended so it would
> > > take into consideration other nodes' systemd instances in order to
> > > make sure each service is always alive somewhere -- call it "floating
> > > units" if you will. :-)
> > > 
> > > Does this idea even make sense? Is it too "one systemd to rule them all"?
> > 
> > Well, I don't really know what exactly HA clusters would need. However,
> > note that we actually do try to draw the line somewhere where systemd
> > ends... I have the suspicion the HA cluster stuff something which could
> > make great use of systemd's comprehensive bus interfaces, but I am not
> > convinced such a project should sit in systemd itself.
> 
>   The RH Cluster suite cares about running services, and restarting services
> when they fail.  Just like systemd.  Main difference is that you can select
> on which host to run this service.  

Well we have "-H" already. What more do you need?

> It could be implemented in some daemon
> synchronising state between remote systemd's.
>   Every time I use ”clustat” I feel like I'm should be looking at
> ”systemctl status” listing.  When I enable services using ”clusvcadm -e foo”
> I feel like it should be ”systemctl enable foo”.  There's a quite big
> overlap between cluster suite and systemctl.

So these tools will walk the cluster and get the status of the
respective service on all machines?

Lennart

-- 
Lennart Poettering - Red Hat, Inc.