From bda084f3310f2ec421a7e3b42aba39b6a206c215 Mon Sep 17 00:00:00 2001
From: Evgenii Stratonikov <evgeniy@morphbits.ru>
Date: Thu, 1 Sep 2022 08:56:21 +0300
Subject: [PATCH] [#1745] writecache: Simplify object counters

Remove unused option and additional pointers to db/fstree.

Signed-off-by: Evgenii Stratonikov <evgeniy@morphbits.ru>
---
 .../writecache/options.go                     | 11 +----
 pkg/local_object_storage/writecache/state.go  | 44 +++----------------
 .../writecache/writecache.go                  | 12 +----
 3 files changed, 8 insertions(+), 59 deletions(-)

diff --git a/pkg/local_object_storage/writecache/options.go b/pkg/local_object_storage/writecache/options.go
index 64e1feba..55020d49 100644
--- a/pkg/local_object_storage/writecache/options.go
+++ b/pkg/local_object_storage/writecache/options.go
@@ -31,8 +31,8 @@ type options struct {
 	// maxCacheSize is the maximum total size of all objects saved in cache (DB + FS).
 	// 1 GiB by default.
 	maxCacheSize uint64
-	// objCounters is an ObjectCounters instance needed for cache size estimation.
-	objCounters ObjectCounters
+	// objCounters contains atomic counters for the number of objects stored in cache.
+	objCounters counters
 	// maxBatchSize is the maximum batch size for the small object database.
 	maxBatchSize int
 	// maxBatchDelay is the maximum batch wait time for the small object database.
@@ -100,13 +100,6 @@ func WithFlushWorkersCount(c int) Option {
 	}
 }
 
-// WithObjectCounters sets ObjectCounters instance needed for cache write-cache size estimation.
-func WithObjectCounters(v ObjectCounters) Option {
-	return func(o *options) {
-		o.objCounters = v
-	}
-}
-
 // WithMaxCacheSize sets maximum write-cache size in bytes.
 func WithMaxCacheSize(sz uint64) Option {
 	return func(o *options) {
diff --git a/pkg/local_object_storage/writecache/state.go b/pkg/local_object_storage/writecache/state.go
index 2885c433..1ba5a4bd 100644
--- a/pkg/local_object_storage/writecache/state.go
+++ b/pkg/local_object_storage/writecache/state.go
@@ -3,33 +3,10 @@ package writecache
 import (
 	"fmt"
 
-	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/blobstor/fstree"
 	"go.etcd.io/bbolt"
 	"go.uber.org/atomic"
 )
 
-// ObjectCounters is an interface of the storage of cached object amount.
-type ObjectCounters interface {
-	// Increments number of objects saved in DB.
-	IncDB()
-	// Decrements number of objects saved in DB.
-	DecDB()
-	// Returns number of objects saved in DB.
-	DB() uint64
-
-	// Increments number of objects saved in FSTree.
-	IncFS()
-	// Decrements number of objects saved in FSTree.
-	DecFS()
-	// Returns number of objects saved in FSTree.
-	FS() uint64
-
-	// Reads number of objects saved in write-cache. It is called on write-cache initialization step.
-	Read() error
-	// Flushes the values and closes the storage. It is called on write-cache shutdown.
-	FlushAndClose()
-}
-
 func (c *cache) estimateCacheSize() uint64 {
 	return c.objCounters.DB()*c.smallObjectSize + c.objCounters.FS()*c.maxObjectSize
 }
@@ -44,10 +21,6 @@ func (c *cache) incSizeFS(sz uint64) uint64 {
 
 type counters struct {
 	cDB, cFS atomic.Uint64
-
-	db *bbolt.DB
-
-	fs *fstree.FSTree
 }
 
 func (x *counters) IncDB() {
@@ -74,33 +47,26 @@ func (x *counters) FS() uint64 {
 	return x.cFS.Load()
 }
 
-func (x *counters) Read() error {
+func (c *cache) initCounters() error {
 	var inDB uint64
-
-	err := x.db.View(func(tx *bbolt.Tx) error {
+	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)
 	}
 
-	x.cDB.Store(inDB)
-
-	inFS, err := x.fs.NumberOfObjects()
+	inFS, err := c.fsTree.NumberOfObjects()
 	if err != nil {
 		return fmt.Errorf("could not read write-cache FS counter: %w", err)
 	}
 
-	x.cFS.Store(inFS)
+	c.objCounters.cDB.Store(inDB)
+	c.objCounters.cFS.Store(inFS)
 
 	return nil
 }
-
-func (x *counters) FlushAndClose() {
-	// values aren't stored
-}
diff --git a/pkg/local_object_storage/writecache/writecache.go b/pkg/local_object_storage/writecache/writecache.go
index 7bd7c583..a4b4fe2e 100644
--- a/pkg/local_object_storage/writecache/writecache.go
+++ b/pkg/local_object_storage/writecache/writecache.go
@@ -124,12 +124,7 @@ func (c *cache) Open(readOnly bool) error {
 	// thus we need to create a channel here.
 	c.closeCh = make(chan struct{})
 
-	c.objCounters = &counters{
-		db: c.db,
-		fs: c.fsTree,
-	}
-
-	return c.objCounters.Read()
+	return c.initCounters()
 }
 
 // Init runs necessary services.
@@ -154,11 +149,6 @@ func (c *cache) Close() error {
 		c.closeCh = nil
 	}
 
-	if c.objCounters != nil {
-		c.objCounters.FlushAndClose()
-		c.objCounters = nil
-	}
-
 	var err error
 	if c.db != nil {
 		err = c.db.Close()