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From "" <>
Subject Re: Length of instance names in Deltacloud
Date Thu, 02 Jun 2011 07:46:46 GMT
Hi Chris:

On 01/06/11 19:18, Chris Lalancette wrote:
> All,
>       We are having a bit of an issue with using condor with deltacloud[1].
> Essentially the issue boils down to the fact that maximum length of an instance
> name is a detail leaking through the deltacloud abstraction.  If I'm using
> gogrid as the backend cloud, then I, as a deltacloud client, currently need
> to know that the maximum length of an instance name is 20 characters.  This
> makes it so that the client application needs to have code like:
> if (gogrid)
>      name = 20characters
> elif (rhevm)
>      name = 50characters
> etc, which breaks the abstraction layer.  Ian Main, Richard Su, and myself have
> been trying to come up with some ideas of how to fix this situation, but we
> have run into a bit of a wall.  The solutions that we have toyed around with
> are:

I like 4) - we already have 'features' which are driver specific params 
- for example the ec2 driver exposes different features for the 
instances collection that the rackspace driver. Adding an attribute to a 
specific feature in order to express a constraint such as 
'string_length' sounds like a good way to go.

> 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

well, yes, but no smarter than we already require the client to be. I 
mean, the client can't make any assumptions about the API - it must 
request the toplevel 'entry point' (e.g. /api/) and then process the 
information to determine what it can do with this particular invocation 
of deltacloud (e.g. does this driver support blob storage? - this is 
only exposed for ec2, rackspace and azure).


> Does anyone have any additional arguments for or against any of these options?
> Or have another idea of how we can stop the name length from leaking through
> the abstraction?

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