From c3a70398018178afac6b8251462f6d7645f6602d Mon Sep 17 00:00:00 2001
From: Dmitrii Stepanov <d.stepanov@yadro.com>
Date: Mon, 27 Feb 2023 16:16:37 +0300
Subject: [PATCH] [TrueCloudLab/hrw#2] node: Optimize shard hash

Compute shard hash only once

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>
---
 pkg/local_object_storage/engine/engine.go     |  4 ++--
 .../engine/engine_test.go                     | 10 +++++++---
 pkg/local_object_storage/engine/shards.go     | 20 +++++++++++--------
 3 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/pkg/local_object_storage/engine/engine.go b/pkg/local_object_storage/engine/engine.go
index f34d5c0bd4..cacb23b8e6 100644
--- a/pkg/local_object_storage/engine/engine.go
+++ b/pkg/local_object_storage/engine/engine.go
@@ -19,7 +19,7 @@ type StorageEngine struct {
 
 	mtx *sync.RWMutex
 
-	shards map[string]shardWrapper
+	shards map[string]hashedShard
 
 	shardPools map[string]util.WorkerPool
 
@@ -223,7 +223,7 @@ func New(opts ...Option) *StorageEngine {
 	return &StorageEngine{
 		cfg:        c,
 		mtx:        new(sync.RWMutex),
-		shards:     make(map[string]shardWrapper),
+		shards:     make(map[string]hashedShard),
 		shardPools: make(map[string]util.WorkerPool),
 		closeCh:    make(chan struct{}),
 		setModeCh:  make(chan setModeRequest),
diff --git a/pkg/local_object_storage/engine/engine_test.go b/pkg/local_object_storage/engine/engine_test.go
index d554d3773f..69514b5320 100644
--- a/pkg/local_object_storage/engine/engine_test.go
+++ b/pkg/local_object_storage/engine/engine_test.go
@@ -21,6 +21,7 @@ import (
 	oidtest "github.com/TrueCloudLab/frostfs-sdk-go/object/id/test"
 	usertest "github.com/TrueCloudLab/frostfs-sdk-go/user/test"
 	"github.com/TrueCloudLab/frostfs-sdk-go/version"
+	"github.com/TrueCloudLab/hrw"
 	"github.com/TrueCloudLab/tzhash/tz"
 	"github.com/panjf2000/ants/v2"
 	"github.com/stretchr/testify/require"
@@ -86,9 +87,12 @@ func testNewEngineWithShards(shards ...*shard.Shard) *StorageEngine {
 			panic(err)
 		}
 
-		engine.shards[s.ID().String()] = shardWrapper{
-			errorCount: atomic.NewUint32(0),
-			Shard:      s,
+		engine.shards[s.ID().String()] = hashedShard{
+			shardWrapper: shardWrapper{
+				errorCount: atomic.NewUint32(0),
+				Shard:      s,
+			},
+			hash: hrw.Hash([]byte(s.ID().String())),
 		}
 		engine.shardPools[s.ID().String()] = pool
 	}
diff --git a/pkg/local_object_storage/engine/shards.go b/pkg/local_object_storage/engine/shards.go
index a6ab92e557..9341be9f9d 100644
--- a/pkg/local_object_storage/engine/shards.go
+++ b/pkg/local_object_storage/engine/shards.go
@@ -16,7 +16,10 @@ import (
 
 var errShardNotFound = logicerr.New("shard not found")
 
-type hashedShard shardWrapper
+type hashedShard struct {
+	shardWrapper
+	hash uint64
+}
 
 type metricsWithID struct {
 	id string
@@ -127,9 +130,12 @@ func (e *StorageEngine) addShard(sh *shard.Shard) error {
 		return fmt.Errorf("shard with id %s was already added", strID)
 	}
 
-	e.shards[strID] = shardWrapper{
-		errorCount: atomic.NewUint32(0),
-		Shard:      sh,
+	e.shards[strID] = hashedShard{
+		shardWrapper: shardWrapper{
+			errorCount: atomic.NewUint32(0),
+			Shard:      sh,
+		},
+		hash: hrw.Hash([]byte(strID)),
 	}
 
 	e.shardPools[strID] = pool
@@ -144,7 +150,7 @@ func (e *StorageEngine) removeShards(ids ...string) {
 		return
 	}
 
-	ss := make([]shardWrapper, 0, len(ids))
+	ss := make([]hashedShard, 0, len(ids))
 
 	e.mtx.Lock()
 	for _, id := range ids {
@@ -276,7 +282,5 @@ func (e *StorageEngine) HandleNewEpoch(epoch uint64) {
 }
 
 func (s hashedShard) Hash() uint64 {
-	return hrw.Hash(
-		[]byte(s.Shard.ID().String()),
-	)
+	return s.hash
 }