On 8/9/13 3:05 PM, Nikolay Starodubtsev wrote:
Hello, Patrick!
We have several reasons to think that for the virtual resources this
possibility is interesting. If we speak about physical resources, user
may use them in the different ways, that's why it is impossible to
include base actions with them to the reservation service. But
speaking about virtual reservations, let's imagine user wants to
reserve virtual machine. He knows everything about it - its
parameters, flavor and time to be leased for. Really, in this case
user wants to have already working (or at least starting to work)
reserved virtual machine and it would be great to include this
opportunity to the reservation service.
We are thinking about base actions for the virtual reservations that
will be supported by Climate, like boot/delete for instance,
create/delete for volume and create/delete for the stacks. The same
will be with volumes, IPs, etc. As for more complicated behaviour, it
may be implemented in Heat. This will make reservations simpler to use
for the end users.
Don't you think so?
Well yes and and no. It really depends upon what you put behind those
lease actions. The view I am trying to sustain is separation of duties
to keep the service simple, ubiquitous and non prescriptive of a certain
kind of usage pattern. In other words, keep Climate for reservation of
capacity (physical or virtual), Heat for orchestration, and so forth.
... Consider for example the case of reservation as a non technical act
but rather as a business enabler for wholesales activities. Don't need,
and probably don't want to start or stop any resource there. I do not
deny that there are cases where it is desirable but then how
reservations are used and composed together at the end of the day mainly
depends on exogenous factors which couldn't be anticipated because they
are driven by the business.
And so, rather than coupling reservations with wired resource
instantiation actions, I would rather couple them with notifications
that everybody can subscribe to (as opposed to the Resource Manager
only) which would let users decide what to do with the life-cycle
events. The what to do may very well be what you advocate i.e. start a
full stack of reserved and interwoven resources, or at the other end of
the spectrum, do nothing at all. This approach IMO would keep things
more open.
P.S. Also we remember about the problem you mentioned some letters ago
- how to guarantee that user will have already working and prepared
host / VM / stack / etc. by the time lease actually starts, no just
"lease begins and preparing process begins too". We are working on it now.
Yes. I think I was explicitly referring to hosts instantiation also
because there is no support of that in Nova API. Climate should support
some kind of "reservation kick-in heads-up" notification whereby the
provider and/or some automated provisioning tools could do the heavy
lifting work of bringing physical hosts online before a hosts
reservation lease starts. I think it doesn't have to be rocket-science
either. It's probably sufficient to make Climate fire up a notification
that say "Lease starting in x seconds", x being an offset value against
T0 that could be defined by the operator based on heuristics. A
dedicated (e.g. IPMI) module of the Resource Manager for hosts
reservation would subscribe as listener to those events.
On Thu, Aug 8, 2013 at 8:18 PM, Patrick Petit <patrick.pe...@bull.net
<mailto:patrick.pe...@bull.net>> wrote:
Hi Nikolay,
Relying on Heat for orchestration is obviously the right thing to
do. But there is still something in your design approach that I am
having difficulties to comprehend since the beginning. Why do you
keep thinking that orchestration and reservation should be treated
together? That's adding unnecessary complexity IMHO. I just don't
get it. Wouldn't it be much simpler and sufficient to say that
there are pools of reserved resources you create through the
reservation service. Those pools could be of different types i.e.
host, instance, volume, network,.., whatever if that's really
needed. Those pools are identified by a unique id that you pass
along when the resource is created. That's it. You know, the AWS
reservation service doesn't even care about referencing a
reservation when an instance is created. The association between
the two just happens behind the scene. That would work in all
scenarios, manual, automatic, whatever... So, why do you care so
much about this in a first place?
Thanks,
Patrick
On 8/7/13 3:35 PM, Nikolay Starodubtsev wrote:
Patrick, responding to your comments:
1) Dina mentioned "start automatically" and "start manually" only
as examples of how these politics may look like. It doesn't seem
to be a correct approach to put orchestration functionality (that
belongs to Heat) in Climate. That's why now we can implement the
basics like starting Heat stack, and for more complex actions we
may later utilize something like Convection (Task-as-a-Service)
project.
2) If we agree that Heat is the main consumer of
Reservation-as-a-Service, we can agree that lease may be created
according to one of the following scenarions (but not multiple):
- a Heat stack (with requirements to stack's contents) as a
resource to be reserved
- some amount of physical hosts (random ones or filtered based on
certain characteristics).
- some amount of individual VMs OR Volumes OR IPs
3) Heat might be the main consumer of virtual reservations. If
not, Heat will require development efforts in order to support:
- reservation of a stack
- waking up a reserved stack
- performing all the usual orchestration work
We will support reservation of individual instance/volume/ IP
etc, but the use case with "giving user already working group of
connected VMs, volumes, networks" seems to be the most
interesting one.
As for Heat autoscaling, reservation of the maximum instances set
in the Heat template (not the minimum value) has to be
implemented in Heat. Some open questions remain though - like
updating of Heat stack when user changes the template to support
higher max number of running instances
4) As a user, I would of course want to have it already working,
running any configured hosts/stacks/etc by the time lease starts.
But in reality we can't predict how much time the preparation
process should take for every single use case. So if you have an
idea how this should be implemented, it would be great you share
your opinion.
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