[node-devel] Support for stateless nodes

[Mike Burns]

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.  

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.

Mike