ceph-csi/pkg/cephfs/controllercache.go

/*
Copyright 2018 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 cephfs

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"os"
	"path"
	"strings"
	"sync"

	"github.com/golang/glog"
)

const (
	controllerCacheRoot = PluginFolder + "/controller/plugin-cache"
)

type controllerCacheEntry struct {
	VolOptions volumeOptions
	VolumeID   volumeID
}

type controllerCacheMap map[volumeID]*controllerCacheEntry

var (
	ctrCache    = make(controllerCacheMap)
	ctrCacheMtx sync.Mutex
)

// Load all .json files from controllerCacheRoot into ctrCache
// Called from driver.go's Run()
func loadControllerCache() error {
	cacheDir, err := ioutil.ReadDir(controllerCacheRoot)
	if err != nil {
		return fmt.Errorf("cannot read controller cache from %s: %v", controllerCacheRoot, err)
	}

	ctrCacheMtx.Lock()
	defer ctrCacheMtx.Unlock()

	for _, fi := range cacheDir {
		if !strings.HasSuffix(fi.Name(), ".json") || !fi.Mode().IsRegular() {
			continue
		}

		f, err := os.Open(path.Join(controllerCacheRoot, fi.Name()))
		if err != nil {
			glog.Errorf("cephfs: cloudn't read '%s' from controller cache: %v", fi.Name(), err)
			continue
		}

		d := json.NewDecoder(f)
		ent := &controllerCacheEntry{}

		if err = d.Decode(ent); err != nil {
			glog.Errorf("cephfs: failed to parse '%s': %v", fi.Name(), err)
		} else {
			ctrCache[ent.VolumeID] = ent
		}

		f.Close()
	}

	return nil
}

func getControllerCacheEntryPath(volId volumeID) string {
	return path.Join(controllerCacheRoot, string(volId)+".json")
}

func (m controllerCacheMap) insert(ent *controllerCacheEntry) error {
	filePath := getControllerCacheEntryPath(ent.VolumeID)

	ctrCacheMtx.Lock()
	defer ctrCacheMtx.Unlock()

	f, err := os.Create(filePath)
	if err != nil {
		return fmt.Errorf("couldn't create cache entry file '%s': %v", filePath, err)
	}
	defer f.Close()

	enc := json.NewEncoder(f)
	if err = enc.Encode(ent); err != nil {
		return fmt.Errorf("failed to encode cache entry for volume %s: %v", ent.VolumeID, err)
	}

	m[ent.VolumeID] = ent

	return nil
}

func (m controllerCacheMap) pop(volId volumeID) (*controllerCacheEntry, error) {
	ctrCacheMtx.Lock()
	defer ctrCacheMtx.Unlock()

	ent, ok := m[volId]
	if !ok {
		return nil, fmt.Errorf("cache entry for volume %s does not exist", volId)
	}

	filePath := getControllerCacheEntryPath(volId)

	if err := os.Remove(filePath); err != nil {
		return nil, fmt.Errorf("failed to remove cache entry file '%s': %v", filePath, err)
	}

	delete(m, volId)

	return ent, nil
}