metrics-server/vendor/k8s.io/apiserver/pkg/registry/generic/registry/storage_factory.go

/*
Copyright 2015 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 registry

import (
	"sync"

	"github.com/golang/glog"

	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apiserver/pkg/registry/generic"
	"k8s.io/apiserver/pkg/storage"
	etcdstorage "k8s.io/apiserver/pkg/storage/etcd"
	"k8s.io/apiserver/pkg/storage/storagebackend"
	"k8s.io/apiserver/pkg/storage/storagebackend/factory"
)

// Creates a cacher based given storageConfig.
func StorageWithCacher(capacity int) generic.StorageDecorator {
	return func(
		storageConfig *storagebackend.Config,
		objectType runtime.Object,
		resourcePrefix string,
		keyFunc func(obj runtime.Object) (string, error),
		newListFunc func() runtime.Object,
		getAttrsFunc storage.AttrFunc,
		triggerFunc storage.TriggerPublisherFunc) (storage.Interface, factory.DestroyFunc) {

		s, d := generic.NewRawStorage(storageConfig)
		if capacity == 0 {
			glog.V(5).Infof("Storage caching is disabled for %T", objectType)
			return s, d
		}
		glog.V(5).Infof("Storage caching is enabled for %T with capacity %v", objectType, capacity)

		// TODO: we would change this later to make storage always have cacher and hide low level KV layer inside.
		// Currently it has two layers of same storage interface -- cacher and low level kv.
		cacherConfig := storage.CacherConfig{
			CacheCapacity:        capacity,
			Storage:              s,
			Versioner:            etcdstorage.APIObjectVersioner{},
			Type:                 objectType,
			ResourcePrefix:       resourcePrefix,
			KeyFunc:              keyFunc,
			NewListFunc:          newListFunc,
			GetAttrsFunc:         getAttrsFunc,
			TriggerPublisherFunc: triggerFunc,
			Codec:                storageConfig.Codec,
		}
		cacher := storage.NewCacherFromConfig(cacherConfig)
		destroyFunc := func() {
			cacher.Stop()
			d()
		}

		// TODO : Remove RegisterStorageCleanup below when PR
		// https://github.com/kubernetes/kubernetes/pull/50690
		// merges as that shuts down storage properly
		RegisterStorageCleanup(destroyFunc)

		return cacher, destroyFunc
	}
}

// TODO : Remove all the code below when PR
// https://github.com/kubernetes/kubernetes/pull/50690
// merges as that shuts down storage properly
// HACK ALERT : Track the destroy methods to call them
// from the test harness. TrackStorageCleanup will be called
// only from the test harness, so Register/Cleanup will be
// no-op at runtime.

var cleanupLock sync.Mutex
var cleanup []func() = nil

func TrackStorageCleanup() {
	cleanupLock.Lock()
	defer cleanupLock.Unlock()

	if cleanup != nil {
		panic("Conflicting storage tracking")
	}
	cleanup = make([]func(), 0)
}

func RegisterStorageCleanup(fn func()) {
	cleanupLock.Lock()
	defer cleanupLock.Unlock()

	if cleanup == nil {
		return
	}
	cleanup = append(cleanup, fn)
}

func CleanupStorage() {
	cleanupLock.Lock()
	old := cleanup
	cleanup = nil
	cleanupLock.Unlock()

	for _, d := range old {
		d()
	}
}