Open Stack

On 16/06/13 05:06, Ryan Lane wrote:
>
> If you use OpenStack you have no choice but to use Keystone. This isn't
> really the case with Designate, and I think it would be difficult for it
> to be a required service. Maybe Keystone could have a driver that
> interacts with Designate for global registry, if Designate is being used?

Yea, I see Designate as something which is entirely optional to an 
OpenStack cloud.

And, as a general purpose DNS service, hosting of the service catalog 
would require no changes on Designate's side.

>
> It really makes sense for this to be a standalone service that other
> services interact with. It's very possible that some infrastructures may
> choose to use Designate to manage their DNS without using any other
> OpenStack service.
>

I absolutely agree, Designate has no hard dependencies on OpenStack 
services and frankly - I see no reason to introduce one. Isolated 
services with a clear and simple goal are always better IMHO than 
interdependent services with everything, even the kitchen sink, included!

I actually think this shows through in Designate's architecture. 
Designate is made up of 4 small and discrete services:

designate-api - A thin API service that provides the HTTP endpoint. This 
deserializes and validates the structure of incoming API calls, and 
forwards them to central.

designate-central - The core of the service. All DB interactions, 
authorization etc happen here.

designate-agent - An optional service that coordinates remote DNS 
servers. Say you decide to use BIND9, you'll need a way to write out the 
zonefiles on each DNS service as changes are made. With PowerDNS, or any 
other DB backed DNS service, this service can be skipped.

designate-sink - Another optional service that hooks into the 
nova/quantum notifications and performs actions based on plugins. For 
example, you could write a plugin to create DNS records for instances as 
they boot. If Designate is incubated, I can see this service being 
deprecated and the relevant hooks being placed straight into 
Nova/Quantum rather than relying on the notification feed.

So - What I'm getting at is, it's possible to use Designate is many 
different ways. Maybe you don't want to host DNS for $customer, but do 
want to maintain forward/reverse DNS for instances.. You can do that by 
running just central and sink[1]. Or maybe you only want to host 
$customers DNS, you just need the central and api services.

Some people see this as complexity, but I see it as series of well 
defined and composable components that can hopefully be used in ways we 
never planned for!

Thanks,
Kiall

[1]: Okay.. So some initial config would require the API.. but it 
wouldn't need to be exposed to customers, or even kept running after the 
initial config.