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Re: [Cluster-devel] unfencing (cman startup)

On Thu, 2009-02-26 at 08:33 -0600, David Teigland wrote:
> On Thu, Feb 26, 2009 at 07:51:57AM +0100, Fabio M. Di Nitto wrote:
> > On Mon, 2009-02-23 at 13:09 -0600, David Teigland wrote:
> > > On Mon, Feb 23, 2009 at 07:52:55PM +0100, Fabio M. Di Nitto wrote:
> > > > > A node unfences *itself* when it boots up.  As such, power-unfencing doesn't
> > > > > make sense; unfencing is only meant to reverse storage fencing.
> > > > 
> > > > What can stop a user to run fence_node -U from another node to do remote
> > > > (un)fencing?
> > > 
> > > It would work.  Users can do anything they like, that's beside the point.
> > 
> > I was thinking about 2 little points..
> > 
> > Given the time at which fence_node -U will fire, you probably want to
> > add a cman_init + cman_is_active + cman_finish loop in fence_node to
> > make sure cman is ready to reply to our ccs queries, otherwise we might
> > have a race condition at boot time (it might be already there.. didn't
> > really check the code). All our daemons do that to give cman time to
> > bootstrap.
> Yes, good point.  I wonder if we'd be better off having cman_tool join
> effectively do an is_active wait before exiting?  Then we could probably
> avoid doing it many other places.  (It's also annoying when corosync crashes
> after is_active completes, but before I've read what I need from cman/ccs.)

hmm.. it might be reasonable to ask cman_tool to do that, but if you
look for example how cmannotifyd works (i know not all daemons can do
that), it can cope with cman going away and coming back (no matter
what's the reason).

> > The second thing would be to set a minimal protection mechanism by
> > allowing fence_node -U to be fired only for the node that it is invoking
> > it. So if we run on node A, fence_node -U can only execute unfencing
> > operations for node A. For testing purposes then we could add a manual
> > override such as "--i-understand-this-operation-can-destroy-the-world".
> I plan to use "fence_node -U" (no name) to unfence self.  I'm inclined to
> just allow any node name after that, but not advertise it.

a bit too late.. we are on a public mailing list ;)


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