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fscache.go
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fscache.go
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package fscache
import (
"errors"
"io/ioutil"
"log"
"path/filepath"
"strings"
"sync"
"github.com/fsnotify/fsnotify"
)
type Watcher struct {
dir string
fswatcher *fsnotify.Watcher
Cache *sync.Map
}
// NewWatch creates a directory watcher and
// updates the cache when any file changes in that dir
func NewWatch(dir string) (*Watcher, error) {
if len(dir) < 1 {
return nil, errors.New("directory is empty")
}
fw, err := fsnotify.NewWatcher()
if err != nil {
return nil, err
}
w := &Watcher{
dir: dir,
fswatcher: fw,
Cache: new(sync.Map),
}
log.Printf("fscache start watcher for %s", w.dir)
err = w.fswatcher.Add(w.dir)
if err != nil {
return nil, err
}
// initial read
err = w.updateCache()
if err != nil {
return nil, err
}
return w, nil
}
// Watch watches for when kubelet updates the volume mount content
func (w *Watcher) Watch() {
go func() {
for {
select {
// it can take up to a 2 minutes for kubelet to recreate the ..data symlink
case event := <-w.fswatcher.Events:
if event.Op&fsnotify.Create == fsnotify.Create {
if filepath.Base(event.Name) == "..data" {
err := w.updateCache()
if err != nil {
log.Printf("fscache update error %v", err)
} else {
log.Printf("fscache reload %s", w.dir)
}
}
}
case err := <-w.fswatcher.Errors:
log.Printf("fswatcher %s error %v", w.dir, err)
}
}
}()
}
// updateCache reads files content and loads them into the cache
func (w *Watcher) updateCache() error {
fileMap := make(map[string]string)
files, err := ioutil.ReadDir(w.dir)
if err != nil {
return err
}
// read files ignoring symlinks and sub directories
for _, file := range files {
name := filepath.Base(file.Name())
if !file.IsDir() && !strings.Contains(name, "..") {
b, err := ioutil.ReadFile(filepath.Join(w.dir, file.Name()))
if err != nil {
return err
}
fileMap[name] = string(b)
}
}
// remove deleted files from cache
w.Cache.Range(func(key interface{}, value interface{}) bool {
_, ok := fileMap[key.(string)]
if !ok {
w.Cache.Delete(key)
}
return true
})
// sync cache
for k, v := range fileMap {
w.Cache.Store(k, v)
}
return nil
}