[Pacemaker] no-quorum-policy = demote?

[Christian Ciach]

2014-05-27 7:34 GMT+02:00 Andrew Beekhof <andrew at beekhof.net>:

>
> On 27 May 2014, at 3:12 pm, Gao,Yan <ygao at suse.com> wrote:
>
> > On 05/27/14 08:07, Andrew Beekhof wrote:
> >>
> >> On 26 May 2014, at 10:47 pm, Christian Ciach <dereineda at gmail.com>
> wrote:
> >>
> >>> I am sorry to get back to this topic, but I'm genuinely curious:
> >>>
> >>> Why is "demote" an option for the ticket "loss-policy" for
> multi-site-clusters but not for the normal "no-quorum-policy" of local
> clusters? This seems like a missing feature to me.
> >>
> >> Or one feature too many.
> >> Perhaps Yan can explain why he wanted demote as an option for the
> loss-policy.
> > Loss-policy="demote" is a kind of natural default if the "Master" mode
> > of a resource requires a ticket like:
> > <rsc_ticket rsc="ms1" rsc-role="Master" ticket="ticketA"/>
> >
> > The idea is for running stateful resource instances across clusters. And
> > loss-policy="demote" provides the possibility if there's the need to
> > still run the resource in slave mode for any reason when losing the
> > ticket, rather than stopping it or fencing the node hosting it.
>
> I guess the same logic applies to the single cluster use-case too and we
> should allow no-quorum-policy=demote.
>
>
Thank you for mentioning this. This was my thought as well.

At the moment we "simulate" this behaviour by using a primitive resource
where "started" means "master" and "stopped" means "slave". This way we can
use "no-quorum-policy=stop" to actually switch the resource to slave on
quorum loss. This seems hacky, so I would appreciate if this could be done
in a proper way some time in the future.


> One question though... do we still stop non-master/slave resources for
> loss-policy=demote?
>
> >
> > Regards,
> >  Yan
> >
> >>
> >>>
> >>> Best regards
> >>> Christian
> >>>
> >>>
> >>> 2014-04-07 9:54 GMT+02:00 Christian Ciach <dereineda at gmail.com>:
> >>> Hello,
> >>>
> >>> I am using Corosync 2.0 with Pacemaker 1.1 on Ubuntu Server 14.04
> (daily builds until final release).
> >>>
> >>> My problem is as follows: I have a 2-node (plus a quorum-node) cluster
> to manage a multistate-resource. One node should be the master and the
> other one the slave. It is absolutely not allowed to have two masters at
> the same time. To prevent a split-brain situation, I am also using a third
> node as a quorum-only node (set to standby). There is no redundant
> connection because the nodes are connected over the internet.
> >>>
> >>> If one of the two nodes managing the resource becomes disconnected, it
> loses quorum. In this case, I want this resource to become a slave, but the
> resource should never be stopped completely! This leaves me with a problem:
> "no-quorum-policy=stop" will stop the resource, while
> "no-quorum-policy=ignore" will keep this resource in a master-state. I
> already tried to demote the resource manually inside the monitor-action of
> the OCF-agent, but pacemaker will promote the resource immediately again.
> >>>
> >>> I am aware that I am trying the manage a multi-site-cluster and there
> is something like the booth-daemon, which sounds like the solution to my
> problem. But unfortunately I need the location-constraints of pacemaker
> based on the score of the OCF-agent. As far as I know location-constraints
> are not possible when using booth, because the 2-node-cluster is
> essentially split into two 1-node-clusters. Is this correct?
> >>>
> >>> To conclude: Is it possible to demote a resource on quorum loss
> instead of stopping it? Is booth an option if I need to manage the location
> of the master based on the score returned by the OCF-agent?
> >>>
> >>>
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> >
> > --
> > Gao,Yan <ygao at suse.com>
> > Software Engineer
> > China Server Team, SUSE.
> >
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> >
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>
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