use plugin registry and prepare for conversion (#1003)

* use plugin registry and prepare for conersion

* Register plugins explicitly to a registry

* check interface impl instead of struc var

* setup plugins at top level

* treat plugin type combinations

* pass registry as arg of V1alpha1ToInternal

* move registry yet another level up

* check interface type separately

cmd/descheduler/app/server.go

@@ -20,6 +20,7 @@ package app
 import (
 	"context"
 	"io"
+	"os"
 	"os/signal"
 	"syscall"
 
@@ -112,3 +113,8 @@ func NewDeschedulerCommand(out io.Writer) *cobra.Command {
 func Run(ctx context.Context, rs *options.DeschedulerServer) error {
 	return descheduler.Run(ctx, rs)
 }
+
+func SetupLogs() {
+	klog.SetOutput(os.Stdout)
+	klog.InitFlags(nil)
+}

cmd/descheduler/descheduler.go

@@ -20,13 +20,13 @@ import (
 	"os"
 
 	"k8s.io/component-base/cli"
-	"k8s.io/klog/v2"
 	"sigs.k8s.io/descheduler/cmd/descheduler/app"
+	"sigs.k8s.io/descheduler/pkg/descheduler"
 )
 
 func init() {
-	klog.SetOutput(os.Stdout)
-	klog.InitFlags(nil)
+	app.SetupLogs()
+	descheduler.SetupPlugins()
 }
 
 func main() {