plugins.go

/*
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 (
	"io"
	"os"
	"sync"

	"github.com/GoogleCloudPlatform/kubernetes/pkg/client"
	"github.com/golang/glog"
)

// Factory is a function that returns a Interface for admission decisions.
// The config parameter provides an io.Reader handler to the factory in
// order to load specific configurations. If no configuration is provided
// the parameter is nil.
type Factory func(client client.Interface, config io.Reader) (Interface, error)

// All registered admission options.
var pluginsMutex sync.Mutex
var plugins = make(map[string]Factory)

// GetPlugins enumerates the
func GetPlugins() []string {
	pluginsMutex.Lock()
	defer pluginsMutex.Unlock()
	keys := []string{}
	for k := range plugins {
		keys = append(keys, k)
	}
	return keys
}

// RegisterPlugin registers a plugin Factory by name.  This
// is expected to happen during app startup.
func RegisterPlugin(name string, plugin Factory) {
	pluginsMutex.Lock()
	defer pluginsMutex.Unlock()
	_, found := plugins[name]
	if found {
		glog.Fatalf("Admission plugin %q was registered twice", name)
	}
	glog.V(1).Infof("Registered admission plugin %q", name)
	plugins[name] = plugin
}

// GetInterface creates an instance of the named plugin, or nil if
// the name is not known.  The error return is only used if the named provider
// was known but failed to initialize. The config parameter specifies the
// io.Reader handler of the configuration file for the cloud provider, or nil
// for no configuration.
func GetPlugin(name string, client client.Interface, config io.Reader) (Interface, error) {
	pluginsMutex.Lock()
	defer pluginsMutex.Unlock()
	f, found := plugins[name]
	if !found {
		return nil, nil
	}
	return f(client, config)
}

// InitPlugin creates an instance of the named interface
func InitPlugin(name string, client client.Interface, configFilePath string) Interface {
	var config *os.File

	if name == "" {
		glog.Info("No admission plugin specified.")
		return nil
	}

	if configFilePath != "" {
		var err error

		config, err = os.Open(configFilePath)
		if err != nil {
			glog.Fatalf("Couldn't open admission plugin configuration %s: %#v",
				configFilePath, err)
		}

		defer config.Close()
	}

	plugin, err := GetPlugin(name, client, config)
	if err != nil {
		glog.Fatalf("Couldn't init admission plugin %q: %v", name, err)
	}
	if plugin == nil {
		glog.Fatalf("Unknown admission plugin: %s", name)
	}

	return plugin
}