Implement basic admission control framework

pkg/admission/chain.go

@@ -0,0 +1,45 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package admission
+
+import ()
+
+// chainAdmissionHandler is an instance of admission.Interface that performs admission control using a chain of admission handlers
+type chainAdmissionHandler []Interface
+
+// New returns an admission.Interface that will enforce admission control decisions
+func newInterface(pluginNames []string, configFilePath string) Interface {
+	plugins := []Interface{}
+	for _, pluginName := range pluginNames {
+		plugin := InitPlugin(pluginName, configFilePath)
+		if plugin != nil {
+			plugins = append(plugins, plugin)
+		}
+	}
+	return chainAdmissionHandler(plugins)
+}
+
+// Admit performs an admission control check using a chain of handlers, and returns immediately on first error
+func (admissionHandler chainAdmissionHandler) Admit(a Attributes) (err error) {
+	for _, handler := range admissionHandler {
+		err := handler.Admit(a)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}