fix: reduce the places where users have to register for using custom plugins (#332)

Author: sanposhiho

simulator/docs/custom-plugin.md

@@ -19,7 +19,7 @@ by passing a default KubeSchedulerConfiguration file via the environment variabl
 
 ### Example
 
-We will explain the case where you want to add [nodenumber](../sample/nodenumber/plugin.go) plugin as example.
+We will explain the case where you want to add [nodenumber](./sample/nodenumber/plugin.go) plugin as example.
 
 The nodenumber plugin is an example plugin that favors nodes that have the number suffix which is the same as the number suffix of the pod name.
 And we can configure it via `NodeNumberArgs`.

simulator/scheduler/config/plugin.go

@@ -7,13 +7,9 @@ import (
 	"k8s.io/kubernetes/pkg/scheduler/framework/runtime"
 )
 
-var (
-	outOfTreeRegistries = runtime.Registry{
-		// TODO(user): add your plugins registries here.
-	}
-
-	registeredOutOfTreeMultiPointName = []string{}
-)
+var outOfTreeRegistries = runtime.Registry{
+	// TODO(user): add your plugins registries here.
+}
 
 // RegisteredMultiPointPluginNames returns all registered multipoint plugin names.
 // in-tree plugins and your original plugins listed in outOfTreeRegistries above.
@@ -43,6 +39,10 @@ func InTreeMultiPointPluginSet() (configv1.PluginSet, error) {
 }
 
 func OutOfTreeMultiPointPluginNames() []string {
+	registeredOutOfTreeMultiPointName := make([]string, 0, len(outOfTreeRegistries))
+	for k := range outOfTreeRegistries {
+		registeredOutOfTreeMultiPointName = append(registeredOutOfTreeMultiPointName, k)
+	}
 	return registeredOutOfTreeMultiPointName
 }
 
@@ -57,6 +57,5 @@ func OutOfTreeRegistries() runtime.Registry {
 func SetOutOfTreeRegistries(r runtime.Registry) {
 	for k, v := range r {
 		outOfTreeRegistries[k] = v
-		registeredOutOfTreeMultiPointName = append(registeredOutOfTreeMultiPointName, k)
 	}
 }