学习高可靠Redis分布式锁实现思路

一、分布式锁的必要性

在单体应用时代，我们使用ReentrantLock或synchronized就能解决线程安全问题。但当系统拆分为分布式架构后（目前大多数公司应该不会只是单体应用了），跨进程的共享资源竞争就成了必须要解决的问题。

分布式锁由此应运而生，但是必须解决三大核心问题：

1. 竞态条件：多人操作共享资源，顺序不可控
2. 锁失效：锁自动过期但业务未执行完，其他客户端抢占资源 / 加锁成功但未设置过期时间，服务宕机导致死锁
3. 锁误删：客户端A释放了客户端B持有的锁。

二、核心实现解析（附源码）

2.1 原子性加锁

local lockKey = KEYS[1]              -- 锁的键名，如"order_lock_123" local lockSecret = ARGV[1]           -- 锁的唯一标识（建议UUID） local expireTime = tonumber(ARGV[2]) -- 过期时间（单位：秒）  -- 参数有效性校验 if not expireTime or expireTime <= 0 then     return "0" -- 参数非法直接返回失败 end  -- 原子操作：SET lockKey lockSecret NX EX expireTime local result = redis.call("set", lockKey, lockSecret, "NX", "EX", expireTime) return result and "1" or "0" -- 成功返回"1"，失败返回"0" 

设计思路：

• value使用客户端唯一标识（推荐SnowflakeID）
• 参数校验：防止传入非法过期时间
• 原子性：单命令完成"判断+设置+过期"操作

2.2 看门狗续期机制

local lockKey = KEYS[1]              -- 锁的键名 local lockSecret = ARGV[1]           -- 锁标识 local expireTime = tonumber(ARGV[2]) -- 新的过期时间  -- 参数校验 if not expireTime or expireTime <= 0 then     return "0" end  -- 获取当前锁的值 local storedSecret = redis.call("get", lockKey)  -- 续期逻辑 if storedSecret == lockSecret then     -- 值匹配则延长过期时间     local result = redis.call("expire", lockKey, expireTime)     return result == 1 and "1" or "0" -- 续期成功返回"1" else     -- 锁不存在或值不匹配     return "0" end 

// 定时续约线程 watchdogExecutor.scheduleAtFixedRate(() -> {     locks.entrySet().removeIf(entry -> entry.getValue().isCancelled());     for (Entry<String, Lock> entry : locks.entrySet()) {         if (!entry.getValue().isCancelled()) {             String result = redisTemplate.execute(RENEWAL_SCRIPT,                  Collections.singletonList(key),                  lock.value, "30");             if ("0".equals(result)) lock.cancel();         }     } }, 0, 10, TimeUnit.SECONDS); 

设计思路：

• 续期间隔=过期时间/3（如30s过期则10s续期）
• 异步线程池需单独配置
• 双重校验锁状态（内存标记+Redis实际值）

2.3 安全释放锁

local lockKey = KEYS[1]       -- 锁的键名 local lockSecret = ARGV[1]    -- 要释放的锁标识  -- 获取当前锁的值 local storedSecret = redis.call("get", lockKey)  -- 校验锁归属 if storedSecret == lockSecret then     -- 值匹配则删除Key     return redis.call("del", lockKey) == 1 and "1" or "0" else     -- 值不匹配     return "0"  end 

设计思路：

• 校验value避免误删其他线程的锁

三、源码

package org.example.tao.util;  import com.alibaba.fastjson2.JSON; import org.springframework.data.redis.core.RedisTemplate; import org.springframework.data.redis.core.script.RedisScript;  import javax.annotation.PreDestroy; import java.util.Collections; import java.util.Map; import java.util.Objects; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.Executors; import java.util.concurrent.ScheduledExecutorService; import java.util.concurrent.TimeUnit;  public class RedisUtils {      static class Lock {         private final String value;         private volatile boolean isCancelled = false;          public Lock(String value) {             this.value = value;         }          public boolean isCancelled() {             return isCancelled;         }          public void cancel() {             isCancelled = true;         }     }      private static final String LOCK_LUA = "local lockKey = KEYS[1]n" + "local lockSecret = ARGV[1]n" + "local expireTime = tonumber(ARGV[2])  -- 动态过期时间n" + "if not expireTime or expireTime <= 0 thenn" + "    return "0"n" + "endn" + "local result = redis.call("set", lockKey, lockSecret, "NX", "EX", expireTime)n" + "return result and "1" or "0"";     private static final String RELEASE_LOCK_LUA = "local lockKey = KEYS[1]n" + "local lockSecret = ARGV[1]n" + "local storedSecret = redis.call("get", lockKey)n" + "if storedSecret == lockSecret thenn" + "    return redis.call("del", lockKey) == 1 and "1" or "0"n" + "elsen" + "    return "0"n" + "end";     private static final String RENEWAL_LUA = "local lockKey = KEYS[1]n" + "local lockSecret = ARGV[1]n" + "local expireTime = tonumber(ARGV[2])n" + "if not expireTime or expireTime <= 0 thenn" + "    return "0"n" + "endn" + "local storedSecret = redis.call("get", lockKey)n" + "if storedSecret == lockSecret thenn" + "    local result = redis.call("expire", lockKey, expireTime)n" + "    return result == 1 and "1" or "0"n" + "elsen" + "    return "0"n" + "end";      private final String defaultExpireTime = "30";     private final RedisTemplate<String, String> redisTemplate;     private final Map<String, Lock> locks = new ConcurrentHashMap<>();     private final ScheduledExecutorService watchdogExecutor = Executors.newScheduledThreadPool(1);      public RedisUtils(RedisTemplate<String, String> redisTemplate) {         this.redisTemplate = redisTemplate;         watchdogExecutor.scheduleAtFixedRate(() -> {             try {                 System.out.println("watchdogExecutor 执行中... locks => " + JSON.toJSONString(locks));                 locks.entrySet().removeIf(entry -> entry.getValue().isCancelled());                 for (Map.Entry<String, Lock> entry : locks.entrySet()) {                     String key = entry.getKey();                     Lock lock = entry.getValue();                     if (!lock.isCancelled()) {                         RedisScript<String> redisScript = RedisScript.of(RENEWAL_LUA, String.class);                         String result = redisTemplate.execute(redisScript, Collections.singletonList(key), lock.value, defaultExpireTime);                         if (Objects.equals(result, "0")) {                             lock.cancel(); // 移除已经释放的锁                         }                     }                 }             } catch (Exception e) {                 System.err.println("看门狗任务执行失败: " + e.getMessage());             }         }, 0, 10, TimeUnit.SECONDS);     }      public boolean acquireLock(String key, String value) {         RedisScript<String> redisScript = RedisScript.of(LOCK_LUA, String.class);         String result = redisTemplate.execute(redisScript, Collections.singletonList(key), value, defaultExpireTime);         if (Objects.equals(result, "1")) {             locks.put(key, new Lock(value));             return true;         }         return false;     }      public boolean acquireLockWithRetry(String key, String value, int maxRetries, long retryIntervalMillis) {         int retryCount = 0;         while (retryCount < maxRetries) {             boolean result = this.acquireLock(key, value);             if (result) {                 locks.put(key, new Lock(value));                 return true;             }             retryCount++;             try {                 Thread.sleep(retryIntervalMillis);             } catch (InterruptedException e) {                 Thread.currentThread().interrupt();                 return false;             }         }         return false;     }      public boolean releaseLock(String key, String value) {         RedisScript<String> redisScript = RedisScript.of(RELEASE_LOCK_LUA, String.class);         String result = redisTemplate.execute(redisScript, Collections.singletonList(key), value);         if (Objects.equals(result, "1")) {             Lock lock = locks.get(key);             if (lock != null) {                 lock.cancel();             }             return true;         }         return false;     }      @PreDestroy     public void shutdown() {         watchdogExecutor.shutdown();         try {             if (!watchdogExecutor.awaitTermination(60, TimeUnit.SECONDS)) {                 watchdogExecutor.shutdownNow();             }         } catch (InterruptedException e) {             watchdogExecutor.shutdownNow();         }     } }  

四、如何使用

4.1 配置类

@Configuration public class AppConfig {      @Resource     private RedisTemplate<String, String> redisTemplate;      @Bean     public RedisUtils init() {         return new RedisUtils(redisTemplate);     }  } 

4.2 使用

@RestController @RequestMapping("/users") public class UserController {     @Resource     private RedisTemplate<String, String> redisTemplate;       @PostMapping("/test2")     public Boolean test2(@RequestBody Map<String, String> map) {         boolean res;         if (Objects.equals(map.get("lockFlag"), "true")) {             res = redisUtils.acquireLock(map.get("key"), map.get("value"));         } else {             res = redisUtils.releaseLock(map.get("key"), map.get("value"));         }         return res;     }  } 

后记

还是免责声明，仅供学习参考