[WIP] Deis-Skydns / Dns Service Discovery

[PierreKircher]

basic unit + deisctl integration to be started as part of platform install

ill squash the commits later on

• create the skydns service as global unit
• add it to install plattform
• have the registry register it self inside skdyns
• change the fleet scheduler to work with the dns based registry
• change the fleet scheduler to publish the app as local dns
• change nginx templates use dns for the reverse proxy

jenkins please !

[deis-bot]

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[mboersma]

Jenkins, add to whitelist.

[bacongobbler]

Since it's not integrated with Deis (yet), should we keep this out of deisctl install/start platform until we start using it? We could still keep it in refresh-units, but just wondering if we should hold off on the platform install.

EDIT: or maybe not?

[gabrtv]

@bacongobbler i think the idea is that we install/start it in this PR (get the infrastructure in place) and then start incorporating it in Deis components in subsequent PRs. Otherwise I'm not sure what the purpose of this PR is.

[PierreKircher]

its 1 pr out of many .. dns allows to get a rid of alot confd work since skydns does internal RR
example the DB or the registry is the best example ..

if you need to connect to the registry you need to lookup inside etcd and get that out .. that requires the container to know etcd / confd .. in terms of a self updating dns .. its as simple as builder.deis.local
n1.router.deis.local n2.router.deis.local .. and so on if you ping router.deis.local its RR between all A Records

so i see a huge value in terms of factoring confd out + internal service discovery on a per app based communication without using the outside net (bandwith / latency) .. since it could be use to connect microservices internaly via dns + env vars ( and keep that env var static )

so key aspects are :

• simplicity via battle proven techologie ( DNS is here since quite some time now )
• the knowledge isolation of containers

im open for all critics / ideas .. so let me know if something is unclear

[PierreKircher]

it need to be started up first if we want to use it for ceph ( as it depends on hostnames ) .. we could use simple dns for that as well ..
so dns system / storage plane / rest ..

and we factor confd out on the fly where it fits.

• reverse proxy in nginx is as simple as passing in the local dns not all the instances anymore

[mattapperson]

This relates to #2715

[johanneswuerbach]

Yeah, this would also allow round-robin dns when running multiple registries or soon to come gateways and bring deis closer to be fully HA.