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 plugins 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
example:github.com/coredns/example
...
The ordering of the plugins is specified by how they 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 assemble 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.