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On 4/10/12 5:36 PM, Justin Santa Barbara wrote:
<blockquote
cite="mid:CAFoXKmoM6sGdMVtxBBKRpAgsD4ye029Msub17qpai=+bC+oRxw@mail.gmail.com"
type="cite">
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<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">The
immediate use case I have in mind is to support this: <a
moz-do-not-send="true"
href="http://wiki.openstack.org/PackageConfigForNova"
target="_blank">http://wiki.openstack.org/PackageConfigForNova</a>
. 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.<br>
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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? </blockquote>
<br>
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:<br>
<br>
<a class="moz-txt-link-freetext" href="http://summit.openstack.org/sessions/view/33">http://summit.openstack.org/sessions/view/33</a><br>
<br>
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.<br>
<br>
Come to think of it, the other session that I have planned
(<a class="moz-txt-link-freetext" href="http://summit.openstack.org/sessions/view/3">http://summit.openstack.org/sessions/view/3</a>) 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.<br>
<br>
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.<br>
<br>
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