[vdsm] Review Request: Add an option to create a watchdog device.

[Ryan Harper]

* Doron Fediuck <dfediuck at redhat.com> [2012-11-22 03:56]:
> 
> ----- Original Message ----- 
> 
> > From: "Sheldon" <shaohef at linux.vnet.ibm.com>
> > To: "Doron Fediuck" <dfediuck at redhat.com>
> > Cc: arch at ovirt.org, "Zheng Sheng ZS Zhou" <zhshzhou at cn.ibm.com>,
> > "Itamar Heim" <iheim at redhat.com>, agl at linux.vnet.ibm.com, "Shu Ming"
> > <shuming at linux.vnet.ibm.com>, "Mark Wu" <wudxw at linux.vnet.ibm.com>,
> > ryanh at us.ibm.com, snmishra at us.ibm.com, danken at redhat.com
> > Sent: Thursday, November 22, 2012 11:00:18 AM
> > Subject: Re: [vdsm] Review Request: Add an option to create a
> > watchdog device.
> 
> > On 11/21/2012 04:00 PM, Doron Fediuck wrote:
> 
> > > > Currently, we do not have any plans to implement the engine side
> > > > of
> > > > the feature.
> > > 
> > 
> > > > But I will add a watchdog feature page to describe how engine
> > > > enable
> > > > this feature. It's definitely great if any engine guy would like
> > > > to
> > > > take the engine part. I will be glad to provide help if needed.
> > > 
> > 
> > > Hi Sheldon,
> > 
> > > Any news on the engine side?
> > 
> > > Currently the vdsm side is merged, while the engine side still
> > > missing.
> > 
> > > The wiki page also lacks the engine side. Can you please handle it?
> > 
> 
> > Hi Doron,
> 
> > I have updated the wiki page.
> > http://wiki.ovirt.org/wiki/Add_an_option_to_create_a_watchdog_device
> > And for vdsm side, I should also add a new patch to report the
> > watchdog event.
> 
> > I can add a flat to vm's status, so engine can poll vm's status to
> > check the event then notify the user, and let the user to take some
> > actions, such as restart or dump guest for analysis.
> > Perhaps event report channel is more better, but I have not find any
> > in vdsm. But it is a big work to add an event register mechanism for
> > vdsm.
> 
> > what's your suggestion?
> 
> > --
> > Sheldon Feng(?????????) <shaohef at linux.vnet.ibm.com> IBM Linux Technology
> > Center
> 
> Hi Sheldon,
> AFAIK, watchdog fires automatically, so no real need for user interaction
> when an event happens. So I'd expect the user to set the relevant action
> before starting the VM. Once the watchdog is triggered, it will do whatever
> action he has set, and notify the user.
> 
> So I'd expect the user to have a list of actions for the watchdog device
> in the engine UI, with a default of none. The user should be able to choose
> which action to set when starting or editing the VM (for next run).

I'd like to suggest we pick something other than none by default since
we've gone through the trouble of configuring and enabling a watchdog.
I think it's worth the discussion of what a better default behavior
should be given access to a watchdog.

I'd suggest that a simple reboot mode would be most useful.

> 
> In the host level, vdsm should get the notification from libvirt, and as
> you suggested report it in the vm stats when polled by the engine. So
> the user can see the notification on a watchdog action taken, and he can still
> stop / restart the VM if he wishes to.
> 
> Does that make sense?

-- 
Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
ryanh at us.ibm.com