nova team mailing list archive

[Michael Gundlach <michael.gundlach@xxxxxxxxxxxxx>]

Hi Ewan,

On Sat, Oct 2, 2010 at 10:46 AM, Ewan Mellor <ewan.mellor@xxxxxxxxxxxxx>wrote:

> On Sat, Oct 02, 2010 at 03:29:57PM +0100, Ewan Mellor wrote:
>
> > In the documentation for the nova.virt layer (in nova.virt.fake) I wrote:
> >
> >     An instance has an ID, which is the identifier chosen by Nova to
> represent
> >     the instance further up the stack.  This is unfortunately also called
> a
> >     'name' elsewhere.  As far as this layer is concerned, 'instance ID'
> and
> >     'instance name' are synonyms.
> >
> >     Note that the instance ID or name is not human-readable or
> >     customer-controlled -- it's an internal ID chosen by Nova.  At the
> >     nova.virt layer, instances do not have human-readable names at all --
> such
> >     things are only known higher up the stack.
> >
> > Is this true any longer?  Looking at nova.db.sqlalchemy.Instance I see
> > fields named id, ec2_id, display_name, and display_description.  What are
> > the semantics of these fields?  How far are these concepts supposed to
> > propagate down the stack?
>

id is the primary key in sqlalchemy -- not stable if we move b/w databases
or shard, so not a candidate for uniquely identifying the instance for all
time.

ec2_id USED TO be the string that the EC2 API used to identify the instance
to the user.

ec2_id is being renamed (in a branch that hasn't hit trunk yet) to
'internal_id' and becoming a long int.  That is the canonical identifier for
an instance, unique for all time and unchanging throughout the life of the
instance.

The EC2 and Rackspace API modules convert 'internal_id' to and from an
API-specific form suitable for showing to users -- in the EC2 case, it's
converted to

  "i-%s" % base_36_representation_of(internal_id)

I've seen some code referring to 'ec2_id' as 'instance_id' (in method params
and such), which is just confusing; I'll be renaming those to internal_id
for consistency before Austin.

I don't know what display_name and display_description are about.

Michael


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