[Pacemaker] Corosync over DHCP IP

[Andrew Beekhof]

On Wed, Feb 13, 2013 at 3:00 PM, Dennis Jacobfeuerborn
<dennisml at conversis.de> wrote:
> On 02/13/2013 01:43 AM, Andrew Beekhof wrote:
>> On Wed, Feb 13, 2013 at 12:52 AM, Dennis Jacobfeuerborn
>> <dennisml at conversis.de> wrote:
>>> On 02/12/2013 03:15 AM, Andrew Beekhof wrote:
>>>> On Tue, Feb 12, 2013 at 1:01 PM, Dennis Jacobfeuerborn
>>>> <dennisml at conversis.de> wrote:
>>>>> On 02/12/2013 02:38 AM, Andrew Beekhof wrote:
>>>>>> On Tue, Feb 12, 2013 at 3:09 AM, Dennis Jacobfeuerborn
>>>>>> <dennisml at conversis.de> wrote:
>>>>>>> On 02/11/2013 11:30 AM, Andrew Beekhof wrote:
>>>>>>>> On Mon, Feb 11, 2013 at 9:24 PM, Viacheslav Biriukov
>>>>>>>> <v.v.biriukov at gmail.com> wrote:
>>>>>>>>> It is VM in the OpenStack. So we can't use static IP.
>>>>>>>>> Right now investigating why interface become down.
>>>>>>>>
>>>>>>>> Even if you solve that, dynamic IP addresses are fundamentally
>>>>>>>> incompatible with cluster software.
>>>>>>>> You're effectively trying to create a cluster out of nodes which
>>>>>>>> change their name every time they boot.
>>>>>>>
>>>>>>> DHCP doesn't necessarily mean a dynamic IP.
>>>>>>
>>>>>> In most (if not all) openstack deployments, it does.
>>>>>> Even better, the static IPs you can assign belong to the physical
>>>>>> hosts and don't show up inside the guests - so corosync can't bind to
>>>>>> them.
>>>>>
>>>>> You are probably talking about the floating IPs. The primary IPs (usually
>>>>> in the 10.0.0.0/8 range) of the interfaces however should work fine for
>>>>> this. There's no magic involved.
>>>>
>>>> If they don't show up in 'ip addr', which they don't in openstack
>>>> guests, then corosync can't use them.
>>>> There is no way to say "Your address is w.x.y.z but you'll get
>>>> messages on a.b.c.d".
>>>
>>> They show up like like any other interface in 'ip addr'.
>>
>> Well something has changed in the last two months then.
>> Because they definitely didn't used to and having spoken to the
>> openstack devs this was by design as floating IPs belong to the host,
>> not the guest.
>
> The floating IP is irrelevant. The primary IP is the one you have to use.

The standard strategy for openstack appears to involve the primary IP
changing on every boot.
This makes the floating IP relevant because the primary IP is unusable
for clustering.

>
>> What version of openstack are your guests running on?
>
> Folsom, but this should be the same in Essex and Diablo as well.
> Also none of this is really OpenStack specific. Having your systems only
> run private IPs and making them available to the outside world using NAT is
> a common setup since long before virtualization even existed.

No kidding.