1+ // src/redis-lock.ts
2+ /**
3+ * Redis Lock Manager
4+ *
5+ * 實現分散式 lock，用於解決高並發寫入時的 lock contention 問題
6+ */
7+
8+ import Redis from 'ioredis' ;
9+
10+ // 生成唯一 token
11+ function generateToken ( ) : string {
12+ return `${ Date . now ( ) } ${ Math . random ( ) . toString ( 36 ) . substring ( 2 , 10 ) } ;
13+ }
14+
15+ export interface LockConfig {
16+ redisUrl ?: string ;
17+ ttl ?: number ; // lock 過期時間（毫秒）
18+ maxWait ?: number ; // 最大等待時間（毫秒）
19+ retryDelay ?: number ; // 重試延遲（毫秒）
20+ }
21+
22+ export class RedisLockManager {
23+ private redis : Redis ;
24+ private defaultTTL = 60000 ; // 60 秒
25+ private maxWait = 60000 ; // 最多等 60 秒
26+ private retryDelay = 100 ; // 初始重試延遲
27+
28+ constructor ( config ?: LockConfig ) {
29+ const redisUrl = config ?. redisUrl || process . env . REDIS_URL || 'redis://localhost:6379' ;
30+ this . redis = new Redis ( redisUrl . replace ( 'redis://' , '' ) , {
31+ lazyConnect : true ,
32+ retryStrategy : ( times ) => {
33+ if ( times > 3 ) return null ; // 放棄重連
34+ return Math . min ( times * 200 , 2000 ) ;
35+ } ,
36+ } ) ;
37+
38+ if ( config ?. ttl ) this . defaultTTL = config . ttl ;
39+ if ( config ?. maxWait ) this . maxWait = config . maxWait ;
40+ }
41+
42+ async connect ( ) : Promise < void > {
43+ try {
44+ await this . redis . connect ( ) ;
45+ } catch ( err ) {
46+ // 如果連不上，尝试不連接（lazy connect）
47+ console . warn ( `[RedisLock] Could not connect to Redis: ${ err } ) ;
48+ }
49+ }
50+
51+ async acquire ( key : string , ttl ?: number ) : Promise < ( ) => Promise < void > > {
52+ const lockKey = `memory-lock:${ key } ;
53+ const token = generateToken ( ) ;
54+ const startTime = Date . now ( ) ;
55+ const lockTTL = ttl || this . defaultTTL ;
56+
57+ // 嘗試連接
58+ let redisAvailable = false ;
59+ try {
60+ await this . redis . ping ( ) ;
61+ redisAvailable = true ;
62+ } catch {
63+ // Redis 不可用，優雅降級 - 回傳 no-op lock
64+ console . warn ( '[RedisLock] Redis unavailable, using no-op lock (allow concurrent)' ) ;
65+ return async ( ) => { } ; // No-op release
66+ }
67+
68+ if ( ! redisAvailable ) {
69+ return async ( ) => { } ;
70+ }
71+
72+ let attempts = 0 ;
73+ while ( true ) {
74+ attempts ++ ;
75+
76+ try {
77+ // 使用 SET NX + token (原子操作)
78+ const result = await this . redis . set ( lockKey , token , 'PX' , lockTTL , 'NX' ) ;
79+
80+ if ( result === 'OK' ) {
81+ // 成功取得 lock
82+ console . log ( `[RedisLock] Acquired lock ${ key } ${ attempts } ) ;
83+
84+ // 回傳帶 token 的 release function
85+ return async ( ) => {
86+ // 用 Lua script 確保只刪除自己的 lock
87+ const script = `
88+ if redis.call("get", KEYS[1]) == ARGV[1] then
89+ return redis.call("del", KEYS[1])
90+ else
91+ return 0
92+ end
93+ ` ;
94+ try {
95+ await this . redis . eval ( script , 1 , lockKey , token ) ;
96+ console . log ( `[RedisLock] Released lock ${ key } ) ;
97+ } catch ( err ) {
98+ console . warn ( `[RedisLock] Failed to release lock: ${ err } ) ;
99+ }
100+ } ;
101+ }
102+ } catch ( err ) {
103+ // 記錄 Redis 錯誤，避免 silent swallow
104+ console . warn ( `[RedisLock] Redis error during acquire (attempt ${ attempts } ${ err } ) ;
105+ }
106+
107+ // 檢查是否超時
108+ if ( Date . now ( ) - startTime > this . maxWait ) {
109+ throw new Error ( `Lock acquisition timeout: ${ key } ${ attempts } ) ;
110+ }
111+
112+ // 指數退避等待
113+ const delay = Math . min ( this . retryDelay * Math . pow ( 1.5 , Math . min ( attempts , 10 ) ) , 2000 ) ;
114+ await this . sleep ( delay + Math . random ( ) * 100 ) ;
115+ }
116+ }
117+
118+ async isHealthy ( ) : Promise < boolean > {
119+ try {
120+ await this . redis . ping ( ) ;
121+ return true ;
122+ } catch {
123+ return false ;
124+ }
125+ }
126+
127+ async disconnect ( ) : Promise < void > {
128+ await this . redis . quit ( ) ;
129+ }
130+
131+ private sleep ( ms : number ) : Promise < void > {
132+ return new Promise ( resolve => setTimeout ( resolve , ms ) ) ;
133+ }
134+ }
135+
136+ /**
137+ * 建立 RedisLockManager 工廠
138+ */
139+ export async function createRedisLockManager ( config ?: LockConfig ) : Promise < RedisLockManager | null > {
140+ const manager = new RedisLockManager ( config ) ;
141+
142+ try {
143+ await manager . connect ( ) ;
144+ const isHealthy = await manager . isHealthy ( ) ;
145+ if ( isHealthy ) {
146+ console . log ( '[RedisLock] Redis lock manager initialized' ) ;
147+ return manager ;
148+ } else {
149+ console . warn ( '[RedisLock] Redis not healthy, will use file lock fallback' ) ;
150+ await manager . disconnect ( ) ;
151+ return null ;
152+ }
153+ } catch ( err ) {
154+ console . warn ( `[RedisLock] Failed to initialize: ${ err } ) ;
155+ return null ;
156+ }
157+ }
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