Compile Time Enabling or Disabling Plugins

Enable or Disable plugins when compiling CoreDNS.

CoreDNS’ plugins (or external plugins) can be enabled or disabled on the fly by specifying (or not specifying) it in the Corefile. But you can also compile CoreDNS with only the plugin you need and leave the rest completely out.

There are two ways to achieve that. It could be done via compile-time configuration file with CoreDNS code base update. It also could be achieved without modifying CoreDNS code.

Build with compile-time configuration file

The with compile-time configuration file, plugin.cfg is all you need to update. It looks like this:

...
whoami:whoami
erratic:erratic
startup:github.com/mholt/caddy/startupshutdown
...

The ordering of the plugins is specified by how the are ordered in this file. Each line consists of a name and a repository. Just add or remove your plugin in this file.

Then do a go get <plugin-repo-path> if you need to get the external plugin’s source code. And then just compile CoreDNS with go generate and a go build. You can then check if CoreDNS has the new plugin with coredns -plugins.

Build with external golang source code

Alternatively, you could assembly plugins from different places through an external golang program. It looks like this:

package main

import (
        _ "github.com/coredns/example"

        "github.com/coredns/coredns/coremain"
        "github.com/coredns/coredns/core/dnsserver"
)

var directives = []string{
        "example",
        ...
        ...
        "whoami",
        "startup",
        "shutdown",
}

func init() {
        dnsserver.Directives = directives
}

func main() {
        coremain.Run()
}

In the above sample code, the external plugin example has been imported with:

        _ "github.com/coredns/example"

The directives should also be updated through:

        dnsserver.Directives = directives

The ordering of the plugins is specified by how the arey ordered in the slice directives.

Then you can just compile CoreDNS with go build to have the binary generated with the plugins you selected.

Miek Gieben
Published: and tagged Documentation using 284 words.