Open Stack

So it's been pointed out that http://169.254.169.254/openstack is completed
OpenStack invented. I don't quite understand how that's not violating the
contract you said we have with end users about EC2 compatibility under the
restriction of 'no new stuff'.

If we added an IPv6 endpoint that the metadata service listens on, it would
just be another place that non cloud-init clients don't know how to talk
to. It's not going to break our compatibility with any clients that connect
to the IPv4 address.
On Sep 5, 2015 3:22 PM, "Sean M. Collins" <sean at coreitpro.com> wrote:

> On Fri, Sep 04, 2015 at 04:20:23PM EDT, Kevin Benton wrote:
> > Right, it depends on your perspective of who 'owns' the API. Is it
> > cloud-init or EC2?
> >
> > At this point I would argue that cloud-init is in control because it
> would
> > be a large undertaking to switch all of the AMI's on Amazon to something
> > else. However, I know Sean disagrees with me on this point so I'll let
> him
> > reply here.
>
>
> Here's my take:
>
> Cloud-Init is a *client* of the Metadata API. The OpenStack Metadata API
> in both the Neutron and Nova projects should all the details of the
> Metadata API that is documented at:
>
>
> http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-metadata.html
>
> This means that this is a compatibility layer that OpenStack has
> implemented so that users can use appliances, applications, and
> operating system images in both Amazon EC2 and an OpenStack environment.
>
> Yes, we can make changes to cloud-init. However, there is no guarantee
> that all users of the Metadata API are exclusively using cloud-init as
> their client. It is highly unlikely that people are rolling their own
> Metadata API clients, but it's a contract we've made with users. This
> includes transport level details like the IP address that the service
> listens on.
>
> The Metadata API is an established API that Amazon introduced years ago,
> and we shouldn't be "improving" APIs that we don't control. If Amazon
> were to introduce IPv6 support the Metadata API tomorrow, we would
> naturally implement it exactly the way they implemented it in EC2. We'd
> honor the contract that Amazon made with its users, in our Metadata API,
> since it is a compatibility layer.
>
> However, since they haven't defined transport level details of the
> Metadata API, regarding IPv6 - we can't take it upon ourselves to pick a
> solution. It is not our API.
>
> The nice thing about config-drive is that we've created a new mechanism
> for bootstrapping instances - by replacing the transport level details
> of the API. Rather than being a link-local address that instances access
> over HTTP, it's a device that guests can mount and read. The actual
> contents of the drive may have a similar schema as the Metadata API, but
> I think at this point we've made enough of a differentiation between the
> EC2 Metadata API and config-drive that I believe the contents of the
> actual drive that the instance mounts can be changed without breaking
> user expectations - since config-drive was developed by the OpenStack
> community. The point being that we call it "config-drive" in
> conversation and our docs. Users understand that config-drive is a
> different feature.
>
> I've had this same conversation about the Security Group API that we
> have. We've named it the same thing as the Amazon API, but then went and
> made all the fields different, inexplicably. Thankfully, it's just the
> names of the fields, rather than being huge conceptual changes.
>
> http://lists.openstack.org/pipermail/openstack-dev/2015-June/068319.html
>
> Basically, I believe that OpenStack should create APIs that are
> community driven and owned, and that we should only emulate
> non-community APIs where appropriate, and explicitly state that we only
> are emulating them. Putting improvements in APIs that came from
> somewhere else, instead of creating new OpenStack branded APIs is a lost
> opportunity to differentiate OpenStack from other projects, as well as
> Amazon AWS.
>
> Thanks for reading, and have a great holiday.
>
> --
> Sean M. Collins
>
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