[Engine-devel] new engine watchdog version

[Omer Frenkel]

----- Original Message -----
> From: "Laszlo Hornyak" <lhornyak at redhat.com>
> To: "Omer Frenkel" <ofrenkel at redhat.com>
> Cc: "engine-devel" <engine-devel at ovirt.org>
> Sent: Monday, March 11, 2013 6:46:06 PM
> Subject: Re: [Engine-devel] new engine watchdog version
> 
> 
> 
> ----- Original Message -----
> > From: "Omer Frenkel" <ofrenkel at redhat.com>
> > To: "Laszlo Hornyak" <lhornyak at redhat.com>
> > Cc: "engine-devel" <engine-devel at ovirt.org>
> > Sent: Monday, March 11, 2013 1:25:39 PM
> > Subject: Re: [Engine-devel] new engine watchdog version
> > 
> > 
> > 
> > ----- Original Message -----
> > > From: "Laszlo Hornyak" <lhornyak at redhat.com>
> > > To: "Omer Frenkel" <ofrenkel at redhat.com>
> > > Cc: "engine-devel" <engine-devel at ovirt.org>
> > > Sent: Monday, March 11, 2013 12:15:39 PM
> > > Subject: Re: [Engine-devel] new engine watchdog version
> > > 
> > > 
> > > 
> > > ----- Original Message -----
> > > > From: "Omer Frenkel" <ofrenkel at redhat.com>
> > > > To: "Laszlo Hornyak" <lhornyak at redhat.com>
> > > > Cc: "engine-devel" <engine-devel at ovirt.org>
> > > > Sent: Monday, March 11, 2013 11:12:48 AM
> > > > Subject: Re: [Engine-devel] new engine watchdog version
> > > > 
> > > > 
> > > > 
> > > > ----- Original Message -----
> > > > > From: "Laszlo Hornyak" <lhornyak at redhat.com>
> > > > > To: "Omer Frenkel" <ofrenkel at redhat.com>
> > > > > Cc: "engine-devel" <engine-devel at ovirt.org>
> > > > > Sent: Monday, March 11, 2013 9:59:53 AM
> > > > > Subject: Re: [Engine-devel] new engine watchdog version
> > > > > 
> > > > > 
> > > > > 
> > > > > ----- Original Message -----
> > > > > > From: "Omer Frenkel" <ofrenkel at redhat.com>
> > > > > > To: "Laszlo Hornyak" <lhornyak at redhat.com>
> > > > > > Cc: "engine-devel" <engine-devel at ovirt.org>
> > > > > > Sent: Sunday, March 10, 2013 8:36:46 AM
> > > > > > Subject: Re: [Engine-devel] new engine watchdog version
> > > > > > 
> > > > > > 
> > > > > > 
> > > > > > ----- Original Message -----
> > > > > > > From: "Laszlo Hornyak" <lhornyak at redhat.com>
> > > > > > > To: "engine-devel" <engine-devel at ovirt.org>
> > > > > > > Sent: Friday, March 8, 2013 7:18:59 PM
> > > > > > > Subject: [Engine-devel] new engine watchdog version
> > > > > > > 
> > > > > > > Hi,
> > > > > > > 
> > > > > > > I uploaded a new version of the watchdog patch. This
> > > > > > > patch
> > > > > > > is
> > > > > > > still
> > > > > > > a
> > > > > > > work in progress, it adds audit log alerts to the
> > > > > > > functionality.
> > > > > > > http://gerrit.ovirt.org/12419/
> > > > > > > 
> > > > > > > Feature page:
> > > > > > > http://www.ovirt.org/Features/Watchdog_engine_support
> > > > > > > 
> > > > > > > Laszlo
> > > > > > > _______________________________________________
> > > > > > > Engine-devel mailing list
> > > > > > > Engine-devel at ovirt.org
> > > > > > > http://lists.ovirt.org/mailman/listinfo/engine-devel
> > > > > > > 
> > > > > > 
> > > > > > Hi,
> > > > > > i looked at the patch and there is something i don't
> > > > > > understand,
> > > > > > i see you are treating the watchdog as a vm device, which
> > > > > > is
> > > > > > great,
> > > > > > so why do we need to save the device details in vm_static
> > > > > > table
> > > > > > in
> > > > > > addition to the vm_devices?
> > > > > > i think its even not used at all (only setting the device
> > > > > > in
> > > > > > command
> > > > > > which could be parameters, no need to persist)
> > > > > > 
> > > > > 
> > > > > Hi Omer,
> > > > > 
> > > > > Thanks, I hoped someone will come up with that question :)
> > > > > The
> > > > > answer
> > > > > is that I followed the established design patterns in the
> > > > > backend.
> > > > > See smartcard and memory balloon, probably others. The
> > > > > motivation
> > > > > for this pattern could be that in case of these devices, you
> > > > > must
> > > > > have the settings in the VM data, not separately in the
> > > > > devices.
> > > > > Also when vdsbroker builds the devices list, it just asks the
> > > > > device
> > > > > list. The redundancy is already there, we can make it
> > > > > differently
> > > > > in
> > > > > this case but that will present the readers with a puzzle:
> > > > > why
> > > > > this
> > > > > pattern in feature X, why that pattern in feature Y...
> > > > > So I would recommend to leave it like this for now and
> > > > > schedule
> > > > > a
> > > > > cleanup on device handling. Devices deserve a cleanup.
> > > > > 
> > > > > Thx,
> > > > > Laszlo
> > > > > 
> > > > 
> > > > i agree there is a mess that requires clean-up,
> > > > but i don't think its a good thing to keep piling up the mess,
> > > > i don't like it that smartcard is there, but some other devices
> > > > are
> > > > ok (balloon and payload)
> > > > so we already have 2 'patterns', lets go with the right one..
> > > > and answering also @Doron's question - yes the device data
> > > > should
> > > > be
> > > > kept with the device
> > > > 
> > > 
> > > Ok, I may have missed the other pattern, could you explain which
> > > one
> > > do you mean?
> > > Balloon does not very different from smartcard, it is there in
> > > VM.
> > > 
> > 
> > the difference is that balloon is not in vm_static table at all
> > (the
> > only place in the db for it is in vm_devices)
> > and smartcard has 'is_smartcard_enabled' field in vm_static in
> > addition to vm_devices (which is not needed..)
> 
> Ok, so what you want is that
> - the engine should query the devices each time the VM record is set
> (from DAO's or Action)
> XOR
> - the client code (rest-api and frontend) should query the devices to
> figure out if the watchdog is there
> 

i prefer this approach, as we do with other sub-collections of vms (disks,networks..)
but if we don't expose devices from the engine, so we need some other way of doing it
(client specific query for "is XXX device enabled?" or engine set it in the VM record as you suggested.

> > 
> > the way i think we (currently) need to work with devices is:
> > add a parameter for it in the parameters, and use it in add/update
> > (/run-once?) (as done for balloon)
> 
> run once for watchdog? why?
> 

for watchdog probably not, i meant in general with devices

> > i don't know what is the use of the field balloonEnabled in VM, i
> > don't see any use of it..
> 
> It is a write-only property.
> 
> > 
> > going forward we need to think if we want to expose devices to
> > frontend,
> > so then we can drop the encapsulation and just use list of devices
> > in
> > VmBase or something like that
> > 
> 
>