[ClusterLabs] Antw: Re: VirtualDomain started in two hosts

[Oscar Segarra]

Hi,

* It is also possible to configure a monitor to ensure that the resource
is not running on nodes where it's not supposed to be (a monitor with
role="Stopped"). You don't have one of these (which is fine, and common).

Can you provide more information/documentation about role="Stopped"

And, please, can you explain how VirtualDomain resource agents manages the
scenario I've presented?

*What happens If I stop pacemaker and corosync services in all nodes and I
start them again... ¿will I have all guests running twice?*

Thanks a lot

2017-01-17 16:38 GMT+01:00 Ken Gaillot <kgaillot at redhat.com>:

> On 01/17/2017 08:52 AM, Ulrich Windl wrote:
> >>>> Oscar Segarra <oscar.segarra at gmail.com> schrieb am 17.01.2017 um
> 10:15 in
> > Nachricht
> > <CAJq8taG8VhX5J1xQpqMRQ-9omFNXKHQs54mBzz491_6df9akzA at mail.gmail.com>:
> >> Hi,
> >>
> >> Yes, I will try to explain myself better.
> >>
> >> *Initially*
> >> On node1 (vdicnode01-priv)
> >>> virsh list
> >> ==============
> >> vdicdb01     started
> >>
> >> On node2 (vdicnode02-priv)
> >>> virsh list
> >> ==============
> >> vdicdb02     started
> >>
> >> --> Now, I execute the migrate command (outside the cluster <-- not
> using
> >> pcs resource move)
> >> virsh migrate --live vdicdb01 qemu:/// qemu+ssh://vdicnode02-priv
> >> tcp://vdicnode02-priv
> >
> > One of the rules of successful clustering is: If resurces are managed by
> the cluster, they are managed by the cluster only! ;-)
> >
> > I guess one node is trying to restart the VM once it vanished, and the
> other node might try to shut down the VM while it's being migrated.
> > Or any other undesired combination...
>
>
> As Ulrich says here, you can't use virsh to manage VMs once they are
> managed by the cluster. Instead, configure your cluster to support live
> migration:
>
> http://clusterlabs.org/doc/en-US/Pacemaker/1.1-pcs/html-
> single/Pacemaker_Explained/index.html#s-migrating-resources
>
> and then use pcs resource move (which is just location constraints under
> the hood) to move VMs.
>
> What's happening in your example is:
>
> * Your VM cluster resource has a monitor operation ensuring that is
> running properly on the desired node.
>
> * It is also possible to configure a monitor to ensure that the resource
> is not running on nodes where it's not supposed to be (a monitor with
> role="Stopped"). You don't have one of these (which is fine, and common).
>
> * When you move the VM, the cluster detects that it is not running on
> the node you told it to keep it running on. Because there is no
> "Stopped" monitor, the cluster doesn't immediately realize that a new
> rogue instance is running on another node. So, the cluster thinks the VM
> crashed on the original node, and recovers it by starting it again.
>
> If your goal is to take a VM out of cluster management without stopping
> it, you can "unmanage" the resource.
>
>
> >> *Finally*
> >> On node1 (vdicnode01-priv)
> >>> virsh list
> >> ==============
> >> *vdicdb01     started*
> >>
> >> On node2 (vdicnode02-priv)
> >>> virsh list
> >> ==============
> >> vdicdb02     started
> >> vdicdb01     started
> >>
> >> If I query cluster pcs status, cluster thinks resource vm-vdicdb01 is
> only
> >> started on node vdicnode01-priv.
> >>
> >> Thanks a lot.
> >>
> >>
> >>
> >> 2017-01-17 10:03 GMT+01:00 emmanuel segura <emi2fast at gmail.com>:
> >>
> >>> sorry,
> >>>
> >>> But do you mean, when you say, you migrated the vm outside of the
> >>> cluster? one server out side of you cluster?
> >>>
> >>> 2017-01-17 9:27 GMT+01:00 Oscar Segarra <oscar.segarra at gmail.com>:
> >>>> Hi,
> >>>>
> >>>> I have configured a two node cluster whewe run 4 kvm guests on.
> >>>>
> >>>> The hosts are:
> >>>> vdicnode01
> >>>> vdicnode02
> >>>>
> >>>> And I have created a dedicated network card for cluster management. I
> >>> have
> >>>> created required entries in /etc/hosts:
> >>>> vdicnode01-priv
> >>>> vdicnode02-priv
> >>>>
> >>>> The four guests have collocation rules in order to make them
> distribute
> >>>> proportionally between my two nodes.
> >>>>
> >>>> The problem I have is that if I migrate a guest outside the cluster, I
> >>> mean
> >>>> using the virsh migrate - - live...  Cluster,  instead of moving back
> the
> >>>> guest to its original node (following collocation sets),  Cluster
> starts
> >>>> again the guest and suddenly I have the same guest running on both
> nodes
> >>>> causing xfs corruption in guest.
> >>>>
> >>>> Is there any configuration applicable to avoid this unwanted behavior?
> >>>>
> >>>> Thanks a lot
>
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