Open Stack

On 4/10/12 5:36 PM, Justin Santa Barbara wrote:
>
>     The immediate use case I have in mind is to support this:
>     http://wiki.openstack.org/PackageConfigForNova .  That design
>     requires periodic checkins between an instance agent and a nova
>     driver.  It certainly /could/ be implemented using ssh, but I
>     originally wrote the design imagining there was a ready-made,
>     standard communication service, and I still think it would be
>     convenient.
>
>
> My concern with that proposal is that it starts simple enough, but 
> then when you want to know e.g. "was the package installed 
> successfully? is the service healthy?" then you need more and more 
> complexity i.e. you end up with PlatformLayer, RedDwarf, Heat, Puppet, 
> Chef or Juju.  So putting a small piece of the required functionality 
> into nova doesn't address your actual use case, which is "I want 
> configured machines, not just the stock images".  It's probably easier 
> to put that logic into your management system of choice, so nova 
> shouldn't do it.  Am I off base here? 

You're not necessarily off base.  WMF has some peculiar needs in this 
regard because in addition to managing instances with puppet we also 
want to use our cloud as a puppet development platform.  I've scheduled 
a discussion about this:

http://summit.openstack.org/sessions/view/33

It would neither shock nor upset me if at the end of that session we 
conclude that I need to just write a private extension for our internal 
use.  Even if that happens, I'll still need a way for Nova to chat with 
instances, though.

Come to think of it, the other session that I have planned 
(http://summit.openstack.org/sessions/view/3) is going to trail off at 
the end with me saying something like "Now that the volumes are created, 
we need to notify existing instances to mount them... somehow."  So 
that's another use case for having a guest agent with runtime nova 
communication.

I continue to suspect that such a service would be widely useful, and 
better than leaving every feature to arrange its own communications.  
The metadata service is almost what I want, I 'just' need it to be 
read/write at runtime.

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