custom-kube-scheduler/kubernetes-v1.15.4/pkg/scheduler/framework/v1alpha1/registry.go

/*
Copyright 2019 The Kubernetes Authors.

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 v1alpha1

import (
	"fmt"

	"k8s.io/apimachinery/pkg/runtime"
)

// PluginFactory is a function that builds a plugin.
type PluginFactory = func(configuration *runtime.Unknown, f FrameworkHandle) (Plugin, error)

// Registry is a collection of all available plugins. The framework uses a
// registry to enable and initialize configured plugins.
// All plugins must be in the registry before initializing the framework.
type Registry map[string]PluginFactory

// Register adds a new plugin to the registry. If a plugin with the same name
// exists, it returns an error.
func (r Registry) Register(name string, factory PluginFactory) error {
	if _, ok := r[name]; ok {
		return fmt.Errorf("a plugin named %v already exists", name)
	}
	r[name] = factory
	return nil
}

// Unregister removes an existing plugin from the registry. If no plugin with
// the provided name exists, it returns an error.
func (r Registry) Unregister(name string) error {
	if _, ok := r[name]; !ok {
		return fmt.Errorf("no plugin named %v exists", name)
	}
	delete(r, name)
	return nil
}

// NewRegistry builds a default registry with all the default plugins.
// This is the registry that Kubernetes default scheduler uses. A scheduler that
// runs custom plugins, can pass a different Registry and when initializing the
// scheduler.
func NewRegistry() Registry {
	return Registry{
		// FactoryMap:
		// New plugins are registered here.
		// example:
		// {
		//  stateful_plugin.Name: stateful.NewStatefulMultipointExample,
		//  fooplugin.Name: fooplugin.New,
		// }
	}
}