federation

README

federation

Name

federation - enables federated queries to be resolved via the kubernetes plugin.

Description

Enabling this plugin allows Federated queries to be resolved via the kubernetes plugin.

Enabling federation without also having kubernetes is a noop.

Syntax

federation [ZONES...] {
    NAME DOMAIN
    upstream [ADDRESS...]
}

• Each NAME and DOMAIN defines federation membership. One entry for each. A duplicate NAME will silently overwrite any previous value.
• upstream [ADDRESS...] defines the upstream resolvers used for resolving the CNAME target produced by this plugin. If no ADDRESS is given, CoreDNS will resolve External Services against itself. ADDRESS can be an IP, an IP:port, or a path to a file structured like resolv.conf.

Examples

Here we handle all service requests in the prod and stage federations.

. {
    kubernetes cluster.local
    federation cluster.local {
        prod prod.feddomain.com
        staging staging.feddomain.com
        upstream
    }
}

Or slightly shorter:

cluster.local {
    kubernetes
    federation {
        prod prod.feddomain.com
        staging staging.feddomain.com
        upstream
    }
}

Documentation

Overview

Package federation implements kubernetes federation. It checks if the qname matches a possible federation. If this is the case and the captured answer is an NXDOMAIN, federation is performed. If this is not the case the original answer is returned.

The federation label is always the 2nd to last once the zone is chopped of. For instance "nginx.mynamespace.myfederation.svc.example.com" has "myfederation" as the federation label. For federation to work we do a normal k8s lookup *without* that label, if that comes back with NXDOMAIN or NODATA(??) we create a federation record and return that.

Federation is only useful in conjunction with the kubernetes plugin, without it is a noop.

Index

• type Federation
  • func New() *Federation
  • func (f *Federation) Name() string
  • func (f *Federation) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error)
• type Func

Types

type Federation

type Federation struct {
	Upstream *upstream.Upstream

	Next        plugin.Handler
	Federations Func
	// contains filtered or unexported fields
}

Federation contains the name to zone mapping used for federation in kubernetes.

func New

func New() *Federation

New returns a new federation.

func (*Federation) Name

func (f *Federation) Name() string

Name implements the plugin.Handle interface.

func (*Federation) ServeDNS

func (f *Federation) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error)

ServeDNS implements the plugin.Handle interface.

type Func

type Func func(state request.Request, fname, fzone string) (msg.Service, error)

Func needs to be implemented by any plugin that implements federation. Right now this is only the kubernetes plugin.