Re: Adding support for manually configured fence_kdump

----- Original Message -----
> From: "Vivek Goyal" 
> To: "Martin Perina" 
> Cc: [e-mail]
> Sent: Thursday, March 13, 2014 9:37:33 PM
> Subject: Re: Adding support for manually configured fence_kdump
>
> On Thu, Mar 13, 2014 at 02:47:08AM -0400, Martin Perina wrote:
> > Hi,
> >
> > we want to integrate support for fence_kdump into oVirt project. Marek Grac
> > pointed me
> > to kexec-tools-2.0.4-23 which contains automatic configuration of
> > fence_kdump from Pacemaker config.
>
> Can you please explain how oVirt cluster is different from regular cluster.
> And why pacemaker is not usable.

oVirt cluster usually contain a lot of nodes (hosts in oVirt terminology),
which can dynamically added/removed to/from cluster. Each host is not
aware of other hosts in cluster, they are all managed by machine on which
oVirt engine is running. Each host is running VDSM which is common gateway
between engine and libvirtd, which manages virtual machines executed on host.
Each host is independent when running its own virtual machines, but engine
manages how and when are virtual machines started/stopped/migrated among
hosts. Each engine can manage multiple clusters.

More info can be found at http://www.ovirt.org/Architecture

So cluster in oVirt term is very different from cluster in Pacemaker term,
and we don't intend to install Pacemaker on oVirt hosts.
> > Unfortunately for us, this support is tightly bound to Pacemaker, so I
> > created attached patch,
>
> Why pacemaker is not usable with Ovirt.
>
> [..]
> > Behavior with this patch
> > when running 'kdumpctl restart' kdump detect if fence_kdump_send
> >
> > binary is installed
> >     and if so, it tries to:
> >   a) It tries to detect is cluster is configured ('pcs' command is
> >   available). If so, it creates
> >      needed config files as described above in steps 1a) and 1b)
> >   b) If cluster is not configured, it tries to detect if
> >   /etc/sysconfig/fence_kdump and
> >      /etc/sysconfig/fence_kdump_nodes exist. If so, fence_kdump is
> >      marked as successfully
> >      configured and kdump continues with steps 1c) and 1d)
>
> Who will generate /etc/sysconfig/fence_kudmp and how?

We plan to extend VDSM to be able to:

- detect if hosts has enabled/configured kdump support, 
  - to save fence_kdump configuration and hosts to which notification will
    be sent
  - to call kdumpctl restart after fence_kdump configuration change

And support for fence_kdump will be included into existing oVirt fencing
mechanism.
> Thanks
> Vivek