fwdpolicy

Name

fwdpolicy - is an alternate version of CoreDNS's forward plugin that adds the ability to define new forwarding policies via plugins.

Description

The fwdpolicy plugin is a copy of the forward plugin from https://github.com/coredns/coredns with an additional feature that enables you to add new policies via external plugins.

Syntax

Syntax is identical to the forward plugin from coredns/coredns. See README-forward.md, which is a copy of the forward plugin README from coredns/coredns.

Forwarding Policy Plugins

Below is a list of forwarding policy plugins that work with this plugin. If you develop a forwarding policy plugin and think it can be useful to others, please submit a PR to add it to this list.

conditional - enables expression based forwarding policies

External Plugin

This is an external plugin. To use it, you must build CoreDNS with this plugin and any forwarding policy plugins added to CoreDNS's plugin.cfg. The fwdpolicy plugin can either replace or be positioned adjacent the built in forward plugin. The relative position of any forwarding policy plugin does not matter, i.e. they can be placed anywhere in the list unless otherwise noted by the forwarding policy plugin's documentation.

Writing a Forwarding Policy Plugin

Any plugin that implements the Policy interface can be used as a forwarding policy plugin.

package fwdpolicy
type Policy interface {
	List(context.Context, []*Proxy, *request.Request) []*Proxy
	String() string
}

List should return an ordered list of Proxy (upstream servers) based on the desired policy behavior. fwdpolicy, exactly as forward plugin will attempt to forward to the returned proxy servers in order received, stopping when successful or total time elapsed exceeds timeout.

String should return the string value used when selecting the policy in the Corefile.

Examples

Forward to upstream servers 10.0.0.10, 10.0.0.11, and 10.0.0.12 using the forwarding policy defined in the mypolicy plugin.

. {
  mypolicy
  fwdpolicy . 10.0.0.10 10.0.0.11 10.0.0.12 {
    policy mypolicy
  }
}

Notes

Originally proposed for CoreDNS's built in forward plugin https://github.com/coredns/coredns/pull/4446.