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

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

pkg/local_object_storage/writecache/writecachebbolt/state.go

@@ -0,0 +1,77 @@
+package writecachebbolt
+
+import (
+	"fmt"
+	"math"
+	"sync/atomic"
+
+	"go.etcd.io/bbolt"
+)
+
+func (c *cache) estimateCacheSize() uint64 {
+	db := c.objCounters.DB() * c.smallObjectSize
+	fstree := c.objCounters.FS() * c.maxObjectSize
+	c.metrics.SetEstimateSize(db, fstree)
+	return db + fstree
+}
+
+func (c *cache) incSizeDB(sz uint64) uint64 {
+	return sz + c.smallObjectSize
+}
+
+func (c *cache) incSizeFS(sz uint64) uint64 {
+	return sz + c.maxObjectSize
+}
+
+type counters struct {
+	cDB, cFS 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 (x *counters) IncFS() {
+	x.cFS.Add(1)
+}
+
+func (x *counters) DecFS() {
+	x.cFS.Add(math.MaxUint64)
+}
+
+func (x *counters) FS() uint64 {
+	return x.cFS.Load()
+}
+
+func (c *cache) initCounters() error {
+	var inDB uint64
+	err := c.db.View(func(tx *bbolt.Tx) error {
+		b := tx.Bucket(defaultBucket)
+		if b != nil {
+			inDB = uint64(b.Stats().KeyN)
+		}
+		return nil
+	})
+	if err != nil {
+		return fmt.Errorf("could not read write-cache DB counter: %w", err)
+	}
+
+	inFS, err := c.fsTree.NumberOfObjects()
+	if err != nil {
+		return fmt.Errorf("could not read write-cache FS counter: %w", err)
+	}
+
+	c.objCounters.cDB.Store(inDB)
+	c.objCounters.cFS.Store(inFS)
+	c.metrics.SetActualCounters(inDB, inFS)
+
+	return nil
+}