Remove empty (invalid) entries from the cache

utils/cache/file_haunter.go

@@ -0,0 +1,121 @@
+package cache
+
+import (
+	"sort"
+	"time"
+
+	"github.com/djherbis/fscache"
+	"github.com/navidrome/navidrome/log"
+)
+
+type haunterKV struct {
+	key   string
+	value fscache.Entry
+	info  fscache.FileInfo
+}
+
+// NewFileHaunter returns a simple haunter which runs every "period"
+// and scrubs older files when the total file size is over maxSize or
+// total item count is over maxItems.  It also removes empty (invalid) files.
+// If maxItems or maxSize are 0, they won't be checked
+//
+// Based on fscache.NewLRUHaunter
+func NewFileHaunter(maxItems int, maxSize int64, period time.Duration) fscache.LRUHaunter {
+	return &fileHaunter{
+		period:   period,
+		maxItems: maxItems,
+		maxSize:  maxSize,
+	}
+}
+
+type fileHaunter struct {
+	period   time.Duration
+	maxItems int
+	maxSize  int64
+}
+
+func (j *fileHaunter) Next() time.Duration {
+	return j.period
+}
+
+func (j *fileHaunter) Scrub(c fscache.CacheAccessor) (keysToReap []string) {
+	var count int
+	var size int64
+	var okFiles []haunterKV
+
+	c.EnumerateEntries(func(key string, e fscache.Entry) bool {
+		if e.InUse() {
+			return true
+		}
+
+		fileInfo, err := c.Stat(e.Name())
+		if err != nil {
+			return true
+		}
+
+		if fileInfo.Size() == 0 {
+			log.Trace("Removing invalid empty file", "file", e.Name())
+			keysToReap = append(keysToReap, key)
+		}
+
+		count++
+		size = size + fileInfo.Size()
+		okFiles = append(okFiles, haunterKV{
+			key:   key,
+			value: e,
+			info:  fileInfo,
+		})
+
+		return true
+	})
+
+	sort.Slice(okFiles, func(i, j int) bool {
+		iLastRead := okFiles[i].info.AccessTime()
+		jLastRead := okFiles[j].info.AccessTime()
+
+		return iLastRead.Before(jLastRead)
+	})
+
+	collectKeysToReapFn := func() bool {
+		var key *string
+		var err error
+		key, count, size, err = j.removeFirst(&okFiles, count, size)
+		if err != nil {
+			return false
+		}
+		if key != nil {
+			keysToReap = append(keysToReap, *key)
+		}
+
+		return true
+	}
+
+	if j.maxItems > 0 {
+		for count > j.maxItems {
+			if !collectKeysToReapFn() {
+				break
+			}
+		}
+	}
+
+	if j.maxSize > 0 {
+		for size > j.maxSize {
+			if !collectKeysToReapFn() {
+				break
+			}
+		}
+	}
+
+	return keysToReap
+}
+
+func (j *fileHaunter) removeFirst(items *[]haunterKV, count int, size int64) (*string, int, int64, error) {
+	var f haunterKV
+
+	f, *items = (*items)[0], (*items)[1:]
+
+	count--
+	size = size - f.info.Size()
+
+	return &f.key, count, size, nil
+}