[#585] writecache: Count items periodically

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

internal/logs/logs.go

@@ -513,4 +513,5 @@ const (
 	FrostFSNodeCantUnmarshalObjectFromDB                                    = "can't unmarshal an object from the DB"   // Error in ../node/cmd/frostfs-node/morph.go
 	RuntimeSoftMemoryLimitUpdated                                           = "soft runtime memory limit value updated"
 	RuntimeSoftMemoryDefinedWithGOMEMLIMIT                                  = "soft runtime memory defined with GOMEMLIMIT environment variable, config value skipped"
+	FailedToCountWritecacheItems                                            = "failed to count writecache items"
 )

pkg/local_object_storage/writecache/writecachebbolt/cachebbolt.go

@@ -107,13 +107,14 @@ func (c *cache) Open(readOnly bool) error {
 	// thus we need to create a channel here.
 	c.closeCh = make(chan struct{})
 
-	return metaerr.Wrap(c.initCounters())
+	return metaerr.Wrap(c.setCounters())
 }
 
 // Init runs necessary services.
 func (c *cache) Init() error {
 	c.metrics.SetMode(c.mode)
 	c.runFlushLoop()
+	c.runDBCounterLoop()
 	return nil
 }
 

pkg/local_object_storage/writecache/writecachebbolt/delete.go

@@ -63,7 +63,6 @@ func (c *cache) Delete(ctx context.Context, addr oid.Address) error {
 			storagelog.OpField("db DELETE"),
 		)
 		deleted = true
-		c.objCounters.DecDB()
 		return nil
 	}
 
@@ -75,7 +74,6 @@ func (c *cache) Delete(ctx context.Context, addr oid.Address) error {
 			storagelog.StorageTypeField(wcStorageType),
 			storagelog.OpField("fstree DELETE"),
 		)
-		c.objCounters.DecFS()
 		deleted = true
 	}
 

pkg/local_object_storage/writecache/writecachebbolt/put.go

@@ -95,7 +95,6 @@ func (c *cache) putSmall(obj objectInfo) error {
 			storagelog.StorageTypeField(wcStorageType),
 			storagelog.OpField("db PUT"),
 		)
-		c.objCounters.IncDB()
 	}
 	return err
 }
@@ -117,7 +116,6 @@ func (c *cache) putBig(ctx context.Context, addr string, prm common.PutPrm) erro
 		c.compressFlags[addr] = struct{}{}
 		c.mtx.Unlock()
 	}
-	c.objCounters.IncFS()
 	storagelog.Write(c.log,
 		storagelog.AddressField(addr),
 		storagelog.StorageTypeField(wcStorageType),

pkg/local_object_storage/writecache/writecachebbolt/state.go

@@ -2,10 +2,13 @@ package writecachebbolt
 
 import (
 	"fmt"
-	"math"
 	"sync/atomic"
+	"time"
 
+	"git.frostfs.info/TrueCloudLab/frostfs-node/internal/logs"
 	"go.etcd.io/bbolt"
+	"go.uber.org/zap"
+	"golang.org/x/sync/errgroup"
 )
 
 func (c *cache) estimateCacheSize() uint64 {
@@ -27,32 +30,21 @@ 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 {
+func (c *cache) setCounters() error {
 	var inDB uint64
+	var inFS uint64
+
+	var eg errgroup.Group
+
+	eg.Go(func() error {
 		err := c.db.View(func(tx *bbolt.Tx) error {
 			b := tx.Bucket(defaultBucket)
 			if b != nil {
@@ -63,18 +55,43 @@ func (c *cache) initCounters() error {
 		if err != nil {
 			return fmt.Errorf("could not read write-cache DB counter: %w", err)
 		}
+		c.objCounters.cDB.Store(inDB)
+		return nil
+	})
 
-	inFS, err := c.fsTree.NumberOfObjects()
+	eg.Go(func() error {
+		var err error
+		inFS, err = c.fsTree.NumberOfObjects()
 		if err != nil {
 			return fmt.Errorf("could not read write-cache FS counter: %w", err)
 		}
 		if inFS > 0 {
 			inFS-- //small.bolt DB file
 		}
-
-	c.objCounters.cDB.Store(inDB)
 		c.objCounters.cFS.Store(inFS)
+		return nil
+	})
+	if err := eg.Wait(); err != nil {
+		return err
+	}
 	c.metrics.SetActualCounters(inDB, inFS)
-
 	return nil
 }
+
+func (c *cache) runDBCounterLoop() {
+	go func() {
+		t := time.NewTicker(time.Second * 30)
+		defer t.Stop()
+		for {
+			select {
+			case <-t.C:
+				err := c.setCounters()
+				if err != nil {
+					c.log.Warn(logs.FailedToCountWritecacheItems, zap.Error(err))
+				}
+			case <-c.closeCh:
+				return
+			}
+		}
+	}()
+}

pkg/local_object_storage/writecache/writecachebbolt/storage.go

@@ -69,7 +69,6 @@ func (c *cache) deleteFromDB(key string) {
 	})
 
 	if err == nil {
-		c.objCounters.DecDB()
 		c.metrics.Evict(writecache.StorageTypeDB)
 		storagelog.Write(c.log,
 			storagelog.AddressField(key),
@@ -111,7 +110,6 @@ func (c *cache) deleteFromDisk(ctx context.Context, keys []string) []string {
 				storagelog.OpField("fstree DELETE"),
 			)
 			c.metrics.Evict(writecache.StorageTypeFSTree)
-			c.objCounters.DecFS()
 			c.estimateCacheSize()
 		}
 	}