[Engine-devel] [node-devel] Support for stateless nodes

[Doron Fediuck]

On 22/02/12 18:08, Mike Burns wrote:
> On Wed, 2012-02-22 at 17:59 +0200, Doron Fediuck wrote:
>> On 22/02/12 17:33, Doron Fediuck wrote:
>>> On 22/02/12 16:57, Mike Burns wrote:
>>>> There has been a lot of interest in being able to run stateless Nodes
>>>> with ovirt-engine.  ovirt-node has designed a way [1] to achieve this on
>>>> the node side, but we need input from the engine and vdsm teams to see
>>>> if we're missing some requirement or if there needs to be changes on the
>>>> engine/vdsm side to achieve this.
>>>>
>>>> As it currently stands, every time you reboot an ovirt-node that is
>>>> stateless, it would require manually removing the host in engine, then
>>>> re-registering/approving it again in engine.  
>>>>
>>>> Any thoughts, concerns, input on how to solve this?
>>>>
>>>> Thanks
>>>>
>>>> Mike
>>>>
>>>> [1] http://ovirt.org/wiki/Node_Stateless
>>>>
>>>
>>> Some points need to be considered;
>>>
>>> - Installation issues
>>>
>>> * Just stating the obvious, which is users need
>>> to remove-add the host on every reboot. This will
>>> not make this feature a lovable one from user's point of view.
>>>
>>> * During initial boot, vdsm-reg configures the networking
>>> and creates a management network bridge. This is a very
>>> delicate process which may fail due to networking issues
>>> such as resolution, routing, etc. So re-doing this on
>>> every boot increases the chances of loosing a node due
>>> to network problems.
>>>
>>> * CA pollution; generating a certificate on each reboot
>>> for each node will create a huge number of certificates
>>> in the engine side, which eventually may damage the CA.
>>> (Unsure if there's a limitation to certificates number,
>>> but having hundreds of junk cert's can't be good).
>>>
>>> * Today there's a supported flow that for nodes with
>>> password, the user is allowed to use the "add host"
>>> scenario. For stateless, it means re-configuring a password
>>> on every boot...
>>>
>>> - Other issues
>>>
>>> * Local storage; so far we were able to define a local
>>> storage in ovirt node. Stateless will block this ability.
>>>
>>> * Node upgrade; currently it's possible to upgrade a node
>>> from the engine. In stateless it will error, since no where
>>> to d/l the iso file to.
>>>
>>> * Collecting information; core dumps and logging may not
>>> be available due to lack of space? Or will it cause kernel
>>> panic if all space is consumed?
>>>
>>
>> One more question / thing to consider;
>> Currently when you manually install a node,
>> you need to configure the management-server's address.
>> Will I need to re-do it on every boot of a stateless node?
> 
> As answered in the other response, there are kernel command line
> parameters to set the management_server.  Since this will likely be in a
> pxe environment, setting the pxe profile to include
> management_server=<engine_url> should be fine.  
> 
I agree it's a valid solution as long as you assume this is relevant
for PXE only use case.

> Another solution could be to setup a specific DNS SRV record that points
> to the ovirt-engine and have node automatically query that for the
> location.
This was discussed in the past and for some reason not implemented.
 
> 
> Mike
> 
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