Optimize saving player data

Saving all players in a single transaction takes the initial save of 100k players from over 3 minutes to under 20 seconds.

Author: eleniums

data/bolt.go

@@ -71,18 +71,20 @@ func (b *BoltDB) LoadPlayers() ([]Player, error) {
 	return players, nil
 }
 
-func (b *BoltDB) SavePlayer(player Player) error {
+func (b *BoltDB) SavePlayers(players []Player) error {
 	err := b.DB.Update(func(tx *bolt.Tx) error {
 		playersBucket := tx.Bucket([]byte(playersBucketName))
 
-		serialized, err := json.Marshal(player)
-		if err != nil {
-			return err
-		}
+		for _, player := range players {
+			serialized, err := json.Marshal(player)
+			if err != nil {
+				return err
+			}
 
-		err = playersBucket.Put([]byte(player.Name), serialized)
-		if err != nil {
-			return err
+			err = playersBucket.Put([]byte(player.Name), serialized)
+			if err != nil {
+				return err
+			}
 		}
 
 		return nil

game/manager.go

@@ -6,6 +6,8 @@ import (
 	"log/slog"
 	"sync"
 	"time"
+
+	"github.com/eleniums/mining-post/data"
 )
 
 const updateInterval = 10 * time.Second
@@ -79,6 +81,8 @@ func (m *Manager) Stop() error {
 
 // Update happens on a regular time interval. This is the main game loop.
 func (m *Manager) update() {
+	slog.Info("Game update starting...")
+
 	startTime := time.Now()
 
 	// stop the world while updating
@@ -89,6 +93,8 @@ func (m *Manager) update() {
 	m.adjustMarketPrices()
 
 	// run updates for each player
+	playerSaveData := make([]data.Player, len(m.players))
+	playerSaveIndex := 0
 	for _, player := range m.players {
 		player.lock.Lock()
 		defer player.lock.Unlock()
@@ -115,14 +121,18 @@ func (m *Manager) update() {
 		if ranks[player.Rank].eligibleForPromotion(player) {
 			player.Rank++
 			player.Title = ranks[player.Rank].Name
-			slog.Info("player was promoted to a new rank", "username", player.Name, "title", player.Title, "rank", player.Rank)
+			slog.Info("Player was promoted to a new rank", "username", player.Name, "title", player.Title, "rank", player.Rank)
 		}
 
-		// last of all, save player data
-		err := m.db.SavePlayer(player.ToDB())
-		if err != nil {
-			slog.Error("Failed to save player data", "username", player.Name, ErrAttr(err))
-		}
+		// prepare player data to be saved
+		playerSaveData[playerSaveIndex] = player.ToDB()
+		playerSaveIndex++
+	}
+
+	// save all player data
+	err := m.db.SavePlayers(playerSaveData)
+	if err != nil {
+		slog.Error("Failed to save player data", ErrAttr(err))
 	}
 
 	slog.Info("Game update finished", "playerCount", len(m.players), "elapsed", time.Since(startTime))

game/storage.go

@@ -8,5 +8,5 @@ type Storage interface {
 	Open(conn string) error
 	Close() error
 	LoadPlayers() ([]data.Player, error)
-	SavePlayer(player data.Player) error
+	SavePlayers(players []data.Player) error
 }