[#421] Try using badger for the write-cache

Signed-off-by: Alejandro Lopez <a.lopez@yadro.com>

pkg/local_object_storage/writecache/writecachebadger/state.go

@@ -0,0 +1,57 @@
+package writecachebadger
+
+import (
+	"fmt"
+	"math"
+	"sync/atomic"
+
+	"github.com/dgraph-io/badger/v4"
+)
+
+func (c *cache) estimateCacheSize() uint64 {
+	onDiskSize, _ := c.db.EstimateSize(nil)
+	c.metrics.SetEstimateSize(onDiskSize, 0)
+	return onDiskSize
+}
+
+func (c *cache) incSizeDB(sz uint64) uint64 {
+	return sz + c.maxObjectSize
+}
+
+type counters struct {
+	cDB atomic.Uint64
+}
+
+func (x *counters) IncDB() {
+	x.cDB.Add(1)
+}
+
+func (x *counters) DecDB() {
+	x.cDB.Add(math.MaxUint64)
+}
+
+func (x *counters) DB() uint64 {
+	return x.cDB.Load()
+}
+
+func (c *cache) initCounters() error {
+	var inDB uint64
+	err := c.db.View(func(tx *badger.Txn) error {
+		opts := badger.DefaultIteratorOptions
+		opts.PrefetchValues = false
+		it := tx.NewIterator(opts)
+		defer it.Close()
+		for it.Rewind(); it.Valid(); it.Next() {
+			inDB++
+		}
+		return nil
+	})
+	if err != nil {
+		return fmt.Errorf("could not read write-cache DB counter: %w", err)
+	}
+
+	c.objCounters.cDB.Store(inDB)
+	c.metrics.SetActualCounters(inDB, 0)
+
+	return nil
+}