perf(gateway): 优化负载感知调度

主要改进：
- 优化负载感知调度的准确性和响应速度
- 将 AccountUsageService 的包级缓存改为依赖注入
- 修复 SSE/JSON 转义和 nil 安全问题
- 恢复 Google One 功能兼容性

backend/internal/repository/concurrency_cache.go

@@ -27,14 +27,8 @@ const (
 	accountSlotKeyPrefix = "concurrency:account:"
 	// 格式: concurrency:user:{userID}
 	userSlotKeyPrefix = "concurrency:user:"
-
-	// Wait queue keys (global structures)
-	// - total: integer total queue depth across all users
-	// - updated: sorted set of userID -> lastUpdateUnixSec (for TTL cleanup)
-	// - counts: hash of userID -> current wait count
-	waitQueueTotalKey   = "concurrency:wait:total"
-	waitQueueUpdatedKey = "concurrency:wait:updated"
-	waitQueueCountsKey  = "concurrency:wait:counts"
+	// 等待队列计数器格式: concurrency:wait:{userID}
+	waitQueueKeyPrefix = "concurrency:wait:"
 	// 账号级等待队列计数器格式: wait:account:{accountID}
 	accountWaitKeyPrefix = "wait:account:"
 
@@ -100,55 +94,27 @@ var (
 	`)
 
 	// incrementWaitScript - only sets TTL on first creation to avoid refreshing
-	// KEYS[1] = total key
-	// KEYS[2] = updated zset key
-	// KEYS[3] = counts hash key
-	// ARGV[1] = userID
-	// ARGV[2] = maxWait
-	// ARGV[3] = TTL in seconds
-	// ARGV[4] = cleanup limit
+	// KEYS[1] = wait queue key
+	// ARGV[1] = maxWait
+	// ARGV[2] = TTL in seconds
 	incrementWaitScript = redis.NewScript(`
-		local totalKey = KEYS[1]
-		local updatedKey = KEYS[2]
-		local countsKey = KEYS[3]
-
-		local userID = ARGV[1]
-		local maxWait = tonumber(ARGV[2])
-		local ttl = tonumber(ARGV[3])
-		local cleanupLimit = tonumber(ARGV[4])
-
-		redis.call('SETNX', totalKey, 0)
-
-		local timeResult = redis.call('TIME')
-		local now = tonumber(timeResult[1])
-		local expireBefore = now - ttl
-
-		-- Cleanup expired users (bounded)
-		local expired = redis.call('ZRANGEBYSCORE', updatedKey, '-inf', expireBefore, 'LIMIT', 0, cleanupLimit)
-		for _, uid in ipairs(expired) do
-			local c = tonumber(redis.call('HGET', countsKey, uid) or '0')
-			if c > 0 then
-				redis.call('DECRBY', totalKey, c)
-			end
-			redis.call('HDEL', countsKey, uid)
-			redis.call('ZREM', updatedKey, uid)
+		local current = redis.call('GET', KEYS[1])
+		if current == false then
+			current = 0
+		else
+			current = tonumber(current)
 		end
 
-		local current = tonumber(redis.call('HGET', countsKey, userID) or '0')
-		if current >= maxWait then
+		if current >= tonumber(ARGV[1]) then
 			return 0
 		end
 
-		local newVal = current + 1
-		redis.call('HSET', countsKey, userID, newVal)
-		redis.call('ZADD', updatedKey, now, userID)
-		redis.call('INCR', totalKey)
+		local newVal = redis.call('INCR', KEYS[1])
 
-		-- Keep global structures from living forever in totally idle deployments.
-		local ttlKeep = ttl * 2
-		redis.call('EXPIRE', totalKey, ttlKeep)
-		redis.call('EXPIRE', updatedKey, ttlKeep)
-		redis.call('EXPIRE', countsKey, ttlKeep)
+		-- Only set TTL on first creation to avoid refreshing zombie data
+		if newVal == 1 then
+			redis.call('EXPIRE', KEYS[1], ARGV[2])
+		end
 
 			return 1
 		`)
@@ -178,111 +144,6 @@ var (
 
 	// decrementWaitScript - same as before
 	decrementWaitScript = redis.NewScript(`
-		local totalKey = KEYS[1]
-		local updatedKey = KEYS[2]
-		local countsKey = KEYS[3]
-
-		local userID = ARGV[1]
-		local ttl = tonumber(ARGV[2])
-		local cleanupLimit = tonumber(ARGV[3])
-
-		redis.call('SETNX', totalKey, 0)
-
-		local timeResult = redis.call('TIME')
-		local now = tonumber(timeResult[1])
-		local expireBefore = now - ttl
-
-		-- Cleanup expired users (bounded)
-		local expired = redis.call('ZRANGEBYSCORE', updatedKey, '-inf', expireBefore, 'LIMIT', 0, cleanupLimit)
-		for _, uid in ipairs(expired) do
-			local c = tonumber(redis.call('HGET', countsKey, uid) or '0')
-			if c > 0 then
-				redis.call('DECRBY', totalKey, c)
-			end
-			redis.call('HDEL', countsKey, uid)
-			redis.call('ZREM', updatedKey, uid)
-		end
-
-		local current = tonumber(redis.call('HGET', countsKey, userID) or '0')
-		if current <= 0 then
-			return 1
-		end
-
-		local newVal = current - 1
-		if newVal <= 0 then
-			redis.call('HDEL', countsKey, userID)
-			redis.call('ZREM', updatedKey, userID)
-		else
-			redis.call('HSET', countsKey, userID, newVal)
-			redis.call('ZADD', updatedKey, now, userID)
-		end
-		redis.call('DECR', totalKey)
-
-		local ttlKeep = ttl * 2
-		redis.call('EXPIRE', totalKey, ttlKeep)
-		redis.call('EXPIRE', updatedKey, ttlKeep)
-		redis.call('EXPIRE', countsKey, ttlKeep)
-
-		return 1
-	`)
-
-	// getTotalWaitScript returns the global wait depth with TTL cleanup.
-	// KEYS[1] = total key
-	// KEYS[2] = updated zset key
-	// KEYS[3] = counts hash key
-	// ARGV[1] = TTL in seconds
-	// ARGV[2] = cleanup limit
-	getTotalWaitScript = redis.NewScript(`
-		local totalKey = KEYS[1]
-		local updatedKey = KEYS[2]
-		local countsKey = KEYS[3]
-
-		local ttl = tonumber(ARGV[1])
-		local cleanupLimit = tonumber(ARGV[2])
-
-		redis.call('SETNX', totalKey, 0)
-
-		local timeResult = redis.call('TIME')
-		local now = tonumber(timeResult[1])
-		local expireBefore = now - ttl
-
-		-- Cleanup expired users (bounded)
-		local expired = redis.call('ZRANGEBYSCORE', updatedKey, '-inf', expireBefore, 'LIMIT', 0, cleanupLimit)
-		for _, uid in ipairs(expired) do
-			local c = tonumber(redis.call('HGET', countsKey, uid) or '0')
-			if c > 0 then
-				redis.call('DECRBY', totalKey, c)
-			end
-			redis.call('HDEL', countsKey, uid)
-			redis.call('ZREM', updatedKey, uid)
-		end
-
-		-- If totalKey got lost but counts exist (e.g. Redis restart), recompute once.
-		local total = redis.call('GET', totalKey)
-		if total == false then
-			total = 0
-			local vals = redis.call('HVALS', countsKey)
-			for _, v in ipairs(vals) do
-				total = total + tonumber(v)
-			end
-			redis.call('SET', totalKey, total)
-		end
-
-		local ttlKeep = ttl * 2
-		redis.call('EXPIRE', totalKey, ttlKeep)
-		redis.call('EXPIRE', updatedKey, ttlKeep)
-		redis.call('EXPIRE', countsKey, ttlKeep)
-
-		local result = tonumber(redis.call('GET', totalKey) or '0')
-		if result < 0 then
-			result = 0
-			redis.call('SET', totalKey, 0)
-		end
-		return result
-	`)
-
-	// decrementAccountWaitScript - account-level wait queue decrement
-	decrementAccountWaitScript = redis.NewScript(`
 			local current = redis.call('GET', KEYS[1])
 			if current ~= false and tonumber(current) > 0 then
 				redis.call('DECR', KEYS[1])
@@ -383,9 +244,7 @@ func userSlotKey(userID int64) string {
 }
 
 func waitQueueKey(userID int64) string {
-	// Historical: per-user string keys were used.
-	// Now we use global structures keyed by userID string.
-	return strconv.FormatInt(userID, 10)
+	return fmt.Sprintf("%s%d", waitQueueKeyPrefix, userID)
 }
 
 func accountWaitKey(accountID int64) string {
@@ -449,16 +308,8 @@ func (c *concurrencyCache) GetUserConcurrency(ctx context.Context, userID int64)
 // Wait queue operations
 
 func (c *concurrencyCache) IncrementWaitCount(ctx context.Context, userID int64, maxWait int) (bool, error) {
-	userKey := waitQueueKey(userID)
-	result, err := incrementWaitScript.Run(
-		ctx,
-		c.rdb,
-		[]string{waitQueueTotalKey, waitQueueUpdatedKey, waitQueueCountsKey},
-		userKey,
-		maxWait,
-		c.waitQueueTTLSeconds,
-		200, // cleanup limit per call
-	).Int()
+	key := waitQueueKey(userID)
+	result, err := incrementWaitScript.Run(ctx, c.rdb, []string{key}, maxWait, c.waitQueueTTLSeconds).Int()
 	if err != nil {
 		return false, err
 	}
@@ -466,35 +317,11 @@ func (c *concurrencyCache) IncrementWaitCount(ctx context.Context, userID int64,
 }
 
 func (c *concurrencyCache) DecrementWaitCount(ctx context.Context, userID int64) error {
-	userKey := waitQueueKey(userID)
-	_, err := decrementWaitScript.Run(
-		ctx,
-		c.rdb,
-		[]string{waitQueueTotalKey, waitQueueUpdatedKey, waitQueueCountsKey},
-		userKey,
-		c.waitQueueTTLSeconds,
-		200, // cleanup limit per call
-	).Result()
+	key := waitQueueKey(userID)
+	_, err := decrementWaitScript.Run(ctx, c.rdb, []string{key}).Result()
 	return err
 }
 
-func (c *concurrencyCache) GetTotalWaitCount(ctx context.Context) (int, error) {
-	if c.rdb == nil {
-		return 0, nil
-	}
-	total, err := getTotalWaitScript.Run(
-		ctx,
-		c.rdb,
-		[]string{waitQueueTotalKey, waitQueueUpdatedKey, waitQueueCountsKey},
-		c.waitQueueTTLSeconds,
-		500, // cleanup limit per query (rare)
-	).Int64()
-	if err != nil {
-		return 0, err
-	}
-	return int(total), nil
-}
-
 // Account wait queue operations
 
 func (c *concurrencyCache) IncrementAccountWaitCount(ctx context.Context, accountID int64, maxWait int) (bool, error) {
@@ -508,7 +335,7 @@ func (c *concurrencyCache) IncrementAccountWaitCount(ctx context.Context, accoun
 
 func (c *concurrencyCache) DecrementAccountWaitCount(ctx context.Context, accountID int64) error {
 	key := accountWaitKey(accountID)
-	_, err := decrementAccountWaitScript.Run(ctx, c.rdb, []string{key}).Result()
+	_, err := decrementWaitScript.Run(ctx, c.rdb, []string{key}).Result()
 	return err
 }