On Wed, 2009-05-20 at 08:08 +0100, Chrissie Caulfield wrote:
> > - if a quorum device exists and it is being reregistered with the same
> > name, just change the votes and recalculate quorum
>
> cman doesn't allow the votes to be changed without deregistering and
> reregistering the quorum device.
>
> I have checked the code and I can't see any reason why doing it this way
> would fail, if register succeeds then it allocates a new node structure
> for the qdisk and populates it from the parameters given.
>
> Is it possible that qdisk might not unregister the qdisk when it is
> stopped under some circumstances ?
It's possible, but unlikely -- it only ever doesn't unregister if it:
(a) hits I/O errors
(b) is killed with -SIGKILL
(c) cman went away (in which case it doesn't matter :) )
I suspect:
if (quorum_device->state == NODESTATE_MEMBER)
return -EBUSY;
... is causing the unregister operation to fail. Maybe I need to call
cman_poll_quorum_device(xxx, 0). It seems a bit odd.
Basically, the use case is online upgrade of # of nodes in the cluster.
3 nodes + 2-vote quorum device ==> 4 nodes + 3-vote quorum device
In my mind, it'd work like:
* Ensure all current members are up and healthy
* each old member sees: votes = 3 + 2
* Update cluster.conf w/ new member.
* Copy cluster.conf to new member
* each old member sees: votes = 4 + 2
* Have new member start cluster stack
* each old member sees: votes = 4 + 2
* the new member sees: votes = 4 + 3
* Stop qdiskd on the old nodes
* each old member sees: votes = 4
* the new member sees: votes = 4 + 3
* Restart qdiskd on the old nodes
* everyone is consistent w/ 4 + 3
I don't think calling poll(0) will make a difference in the above case,
but I had gotten used to the fact that if you kill qdiskd you had a few
seconds to restart it before CMAN noticed...
So, I can fix it I think with poll(0), but if an admin kills qdiskd with
SIGKILL (or any other fatal signal), restarting qdiskd will prevent
correct vote registration (though as I have found out, polling still
works great).
-- Lon
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