[Linux-ha-dev] new stonith external plugin

[Serge Dubrouski]

On 1/29/07, Andrew Beekhof <beekhof at gmail.com> wrote:
> On 1/29/07, Serge Dubrouski <sergeyfd at gmail.com> wrote:
> > On 1/29/07, Lars Marowsky-Bree <lmb at suse.de> wrote:
> > > On 2007-01-29T10:10:44, Andrew Beekhof <beekhof at gmail.com> wrote:
> > >
> > > > >Attached is an update version. It supports on and off commands now.
> > > > >User still have to configure hostlist in a form "node:xen0_host
> > > > >node:xen0_host ...".
> > > > thats going to be a pain when the VMs are also resources (and therefor
> > > > moving around).
> > > >
> > > > or aren't we dealing with this case here?  i loose track sometimes :-)
> > >
> > > That's not being dealt with, AFAIK. In that case, the command wouldn't
> > > be a xm shutdown/start, but a "crm_resource ..." invocation; potentially
> > > one trying to stop a specific clone. I'm not sure _you_ want to deal
> > > with that yet. ;-)
> > >
> > > However, I think it could be simplified.
> > >
> > > First, in many cases, all the virtual guests are going to be on a single
> > > physical node. (ie, test "clusters".) Then only supplying one node to
> > > ssh to should be sufficient.
> >
> > Let's nod discuss trivial cases.
> >
> > >
> > > Second, by providing a simple list of all physical nodes, the system
> > > should be able to automatically figure out which node it needs to ssh to
> > > to shot the guest. It could try to autopopulate the hostlist from
> > > /etc/xen/vm/* or some other directory, as well.
> >
> > Ok, Let's say user provided us with 3 Xen0 Nodes and ALL 3 of them
> > have config file for node1 in /etc/xen/vm. Then where should I start
> > node1 when "on" command is called?
>
>
> wouldn't you just use the same node name that you used for "off"?
>
> or are "on" and "off" distinct operations sent to you from the stonithd?
>
> by that i mean that stonithd will never just tell you to turn a node
> on, only to stop or reset it in some way.  so if you were able to do
> the "off", then you know you can also do the "on".
>

That means that I'll have to keep a track of previous calls which I
actually don't want to do. The problem is that I couldn't find any
documentation on STONITH specifications and just used ssh plugin as an
example. I don't know in what order commands can be sent to me and
what should I do if I receive "on" without previous "off". Actually
"on" is the most complex thing if I didn't have to implement it I
could go with a simple list of all possible Xen0s (like Lars said) and
easily implement "off" and "reset".
Another problem is that I don't want to do any complex tasks on
"status" command. Status is called very often (every 5s or so) and
putting complex logic (especially calling ssh to check Xen nodes) on
that function would be too expensive.