Open Stack

Hi Steven,

Thanks for your explanation on Heat.

> -----Original Message-----
> From: Steven Hardy [mailto:shardy at redhat.com]
> Sent: Friday, January 16, 2015 5:12 PM
> To: Duan, Li-Gong (Gary at HPServers-Core-OE-PSC)
> Cc: openstack at lists.openstack.org
> Subject: Re: [Openstack] [Heat] Heat supports OpenStack operation
> 
> On Fri, Jan 16, 2015 at 08:34:47AM +0000, Duan, Li-Gong (Gary at HPServers-
> Core-OE-PSC) wrote:
> >    Does Heat support executing an OpenStack operation, such as migrating
> an
> >    Nova instance, powering off a Nova instance?
> 
> We call state changes which don't affect the definition of the stack an
> "action", and we only support suspend and resume at present (e.g heat
> action-suspend <stack name>)

It does make sense in that Heat centers around stack and does a great job 
In stack operation.
 
> It may be possible to add support for more actions (until now nobody has
> asked for them), but note it only really makes sense to drive such actions via
> heat when dependencies/ordering are important.

> For example, when suspending then resuming a stack containing a
> WebServer instance and a DatabaseServer instance, you want
> DatabaseServer to be resumed before WebServer (same order as on stack
> create)
> 
> So, it might make sense to have an action which can power-off a whole stack,
> turning off each nova node in the right order (you could write a little script
> which does the same thing quite easily though..).

It is an easy job to write a script to implement such actions as turning off each 
Nova node. But I would like to figure out a more elegant way to do it, for
example, automatically turning off each Nova node at a specified condition.
This can be implemented by using Ceilometer::Alarm to implement triggering
this operation, but it seems that there is no appropriate place/component to 
implement the action (say, turning off each nova node). That's the reason why
I want to see whether Heat can supports such operations. 

> It probably doesn't make much sense for heat to support things like
> migrating an instance, since it's an operation which isn't scoped to the stack
> and it's dependencies, it's likely an operator wants to migrate a workload off
> a specific compute node, which is something Heat has no visibility of at all.
> 
> >    I know currently Heat does a good job on launching cloud cluster or
> >    application, such as deploying a Nova instance with specified network
> >    configuration, but not sure how to control(not launch or delete) a Nova
> >    instance or cinder volume.
> 
> Right now, the easiest answer is write a little script which uses information
> from heat (e.g to get the UUID's for the resources you want to
> control) then e.g calls nova.

As mentioned above, the basic idea is to trigger a specified set of operations
once a specified condition is reached. In this case, monitoring the condition 
and trigger action can be implemented with Ceilometer::Alarm, but I want to
see whether it is possible to implement the set of operations in Heat template.

Considering that Heat is dealing with sets of resources(stack), I am wondering 
whether it can deal with sets of operations, too.

> >    If Heat does not support these OpenStack operation, what is the best
> Heat
> >    way if we want to execute some operations, such as powering off a Nova
> >    instance, in Heat template?
> 
> As mentioned above, these lifecycle operations affect the stack state, but
> not it's definition, so it probably doesn't make sense to expose actions like
> powering off an instance in the heat template.

Now I understand that it doesn't make much sense to implement operation set 
in heat template and I need to figure other way to implement the set of 
operations.

Regards,
Gary