Custom plugin config should take precedence over default plugin config

Signed-off-by: Dave Chen <dave.chen@arm.com>

pkg/scheduler/apis/config/v1beta2/default_plugins.go

@@ -147,19 +147,34 @@ func mergePlugins(defaultPlugins, customPlugins *v1beta2.Plugins) *v1beta2.Plugi
 	return defaultPlugins
 }
 
+type pluginIndex struct {
+	index  int
+	plugin v1beta2.Plugin
+}
+
 func mergePluginSet(defaultPluginSet, customPluginSet v1beta2.PluginSet) v1beta2.PluginSet {
 	disabledPlugins := sets.NewString()
+	enabledCustomPlugins := make(map[string]pluginIndex)
 	for _, disabledPlugin := range customPluginSet.Disabled {
 		disabledPlugins.Insert(disabledPlugin.Name)
 	}
-
+	for index, enabledPlugin := range customPluginSet.Enabled {
+		enabledCustomPlugins[enabledPlugin.Name] = pluginIndex{index, enabledPlugin}
+	}
 	var enabledPlugins []v1beta2.Plugin
 	if !disabledPlugins.Has("*") {
 		for _, defaultEnabledPlugin := range defaultPluginSet.Enabled {
 			if disabledPlugins.Has(defaultEnabledPlugin.Name) {
 				continue
 			}
-
+			// The default plugin is explicitly re-configured, update the default plugin accordingly.
+			if customPlugin, ok := enabledCustomPlugins[defaultEnabledPlugin.Name]; ok {
+				klog.InfoS("Defaut plugin is explicitly re-configured and is overriding.", "plugin", defaultEnabledPlugin.Name)
+				// update the default plugin in place to preserve order
+				defaultEnabledPlugin = customPlugin.plugin
+				// kick the plugin from the enabled list of custom plugins
+				customPluginSet.Enabled = append(customPluginSet.Enabled[:customPlugin.index], customPluginSet.Enabled[customPlugin.index+1:]...)
+			}
 			enabledPlugins = append(enabledPlugins, defaultEnabledPlugin)
 		}
 	}

pkg/scheduler/apis/config/v1beta2/default_plugins_test.go

@@ -359,6 +359,58 @@ func TestMergePlugins(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "CustomPluginOverrideDefaultPlugin",
+			customPlugins: &v1beta2.Plugins{
+				Filter: v1beta2.PluginSet{
+					Enabled: []v1beta2.Plugin{
+						{Name: "Plugin1", Weight: pointer.Int32Ptr(2)},
+					},
+				},
+			},
+			defaultPlugins: &v1beta2.Plugins{
+				Filter: v1beta2.PluginSet{
+					Enabled: []v1beta2.Plugin{
+						{Name: "Plugin1"},
+					},
+				},
+			},
+			expectedPlugins: &v1beta2.Plugins{
+				Filter: v1beta2.PluginSet{
+					Enabled: []v1beta2.Plugin{
+						{Name: "Plugin1", Weight: pointer.Int32Ptr(2)},
+					},
+				},
+			},
+		},
+		{
+			name: "OrderPreserveAfterOverride",
+			customPlugins: &v1beta2.Plugins{
+				Filter: v1beta2.PluginSet{
+					Enabled: []v1beta2.Plugin{
+						{Name: "Plugin2", Weight: pointer.Int32Ptr(2)},
+					},
+				},
+			},
+			defaultPlugins: &v1beta2.Plugins{
+				Filter: v1beta2.PluginSet{
+					Enabled: []v1beta2.Plugin{
+						{Name: "Plugin1"},
+						{Name: "Plugin2"},
+						{Name: "Plugin3"},
+					},
+				},
+			},
+			expectedPlugins: &v1beta2.Plugins{
+				Filter: v1beta2.PluginSet{
+					Enabled: []v1beta2.Plugin{
+						{Name: "Plugin1"},
+						{Name: "Plugin2", Weight: pointer.Int32Ptr(2)},
+						{Name: "Plugin3"},
+					},
+				},
+			},
+		},
 	}
 
 	for _, test := range tests {

staging/src/k8s.io/kube-scheduler/config/v1beta2/types.go

@@ -197,6 +197,8 @@ type Plugins struct {
 // If an array is empty, missing, or nil, default plugins at that extension point will be used.
 type PluginSet struct {
 	// Enabled specifies plugins that should be enabled in addition to default plugins.
+	// If the default plugin is also configured in the scheduler config file, the weight of plugin will
+	// be overridden accordingly.
 	// These are called after default plugins and in the same order specified here.
 	// +listType=atomic
 	Enabled []Plugin `json:"enabled,omitempty"`