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Subject: Re: Length of instance names in Deltacloud
From: David Lutterkort <lutter@redhat.com>
To: Chris Lalancette <clalance@redhat.com>
Cc: deltacloud-dev@incubator.apache.org, imain@redhat.com,
        Richard Su
 <rwsu@redhat.com>, David Lutterkort <dlutter@redhat.com>
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Organization: Red Hat Inc
Date: Thu, 02 Jun 2011 10:27:18 +0200
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X-Scanned-By: MIMEDefang 2.68 on 10.5.11.23

On Wed, 2011-06-01 at 12:18 -0400, Chris Lalancette wrote:
> 4)  Export the name length restriction through some sort of deltacloud feature.
> Then the client can look at the restriction, and generate a name conforming
> to the restriction.
> 
> Pros: Requires very little change in deltacloud itself.  Pushes the problem out
> to the client
> Cons: Pushes the problem out to the client ;).  Sort of breaks the cloud
> abstraction by having to have the client be smarter

>From the API side, I see this as the only practical option - anything
else would add some sort of application logic to the API. It would also
require some name remapping scheme: Deltacloud says the instance is
called 'frobnez' when the cloud provider calls it 'i-123476'. That means
there's yet another piece of data that admins need to hang on to, with
devastating consequences if they don't.

In practical terms, we already have a feature 'user_name' for instances
that indicates that the clouds supports user-supplied names. We could
just enhance the XML to include the maximum size, e.g.

        <api driver="..." version="...">
                <link href="http://localhost:3001/api/instances" rel="instances">
                    <feature name="user_name">
                        <param name="name">
                                  <constraint name="max_length"
                                value="20"/>
                                  <constraint name="pattern"
                                value="[a-zA-Z0-9]+"/>
                                </param>
                    </feature>
                </link>
        </api>

(The pattern stuff as an example of something we don't need right now,
but might want to add at some point)

David