學(xué)習(xí)高可靠Redis分布式鎖實(shí)現(xiàn)思路

一、分布式鎖的必要性

在單體應(yīng)用時(shí)代，我們使用ReentrantLock或synchronized就能解決線程安全問題。但當(dāng)系統(tǒng)拆分為分布式架構(gòu)后（目前大多數(shù)公司應(yīng)該不會(huì)只是單體應(yīng)用了），跨進(jìn)程的共享資源競(jìng)爭(zhēng)就成了必須要解決的問題。

分布式鎖由此應(yīng)運(yùn)而生，但是必須解決三大核心問題：

競(jìng)態(tài)條件：多人操作共享資源，順序不可控
鎖失效：鎖自動(dòng)過期但業(yè)務(wù)未執(zhí)行完，其他客戶端搶占資源 / 加鎖成功但未設(shè)置過期時(shí)間，服務(wù)宕機(jī)導(dǎo)致死鎖
鎖誤刪：客戶端A釋放了客戶端B持有的鎖。

二、核心實(shí)現(xiàn)解析（附源碼）

2.1 原子性加鎖

local lockKey = KEYS[1]              -- 鎖的鍵名，如"order_lock_123"
local lockSecret = ARGV[1]           -- 鎖的唯一標(biāo)識(shí)（建議UUID）
local expireTime = tonumber(ARGV[2]) -- 過期時(shí)間（單位：秒）

-- 參數(shù)有效性校驗(yàn)
if not expireTime or expireTime <= 0 then
    return "0" -- 參數(shù)非法直接返回失敗
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"，失敗返回"0"

設(shè)計(jì)思路：

lockSecret 使用客戶端唯一標(biāo)識(shí)（推薦SnowflakeID）
參數(shù)校驗(yàn)：防止傳入非法過期時(shí)間
原子性：?jiǎn)蚊钔瓿?判斷+設(shè)置+過期"操作

2.2 看門狗續(xù)期機(jī)制

local lockKey = KEYS[1]              -- 鎖的鍵名
local lockSecret = ARGV[1]           -- 鎖標(biāo)識(shí)
local expireTime = tonumber(ARGV[2]) -- 新的過期時(shí)間

-- 參數(shù)校驗(yàn)
if not expireTime or expireTime <= 0 then
    return "0"
end

-- 獲取當(dāng)前鎖的值
local storedSecret = redis.call("get", lockKey)

-- 續(xù)期邏輯
if storedSecret == lockSecret then
    -- 值匹配則延長(zhǎng)過期時(shí)間
    local result = redis.call("expire", lockKey, expireTime)
    return result == 1 and "1" or "0" -- 續(xù)期成功返回"1"
else
    -- 鎖不存在或值不匹配
    return "0"
end

// 定時(shí)續(xù)約線程
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);

設(shè)計(jì)思路：

續(xù)期間隔=過期時(shí)間/3（如30s過期則10s續(xù)期）
異步線程池需單獨(dú)配置
雙重校驗(yàn)鎖狀態(tài)（內(nèi)存標(biāo)記+Redis實(shí)際值）

2.3 安全釋放鎖

local lockKey = KEYS[1]       -- 鎖的鍵名
local lockSecret = ARGV[1]    -- 要釋放的鎖標(biāo)識(shí)

-- 獲取當(dāng)前鎖的值
local storedSecret = redis.call("get", lockKey)

-- 校驗(yàn)鎖歸屬
if storedSecret == lockSecret then
    -- 值匹配則刪除Key
    return redis.call("del", lockKey) == 1 and "1" or "0"
else
    -- 值不匹配
    return "0" 
end

設(shè)計(jì)思路：

校驗(yàn)value避免誤刪其他線程的鎖

三、源碼

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])  -- 動(dòng)態(tài)過期時(shí)間\n" + "if not expireTime or expireTime <= 0 then\n" + "    return \"0\"\n" + "end\n" + "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 then\n" + "    return redis.call(\"del\", lockKey) == 1 and \"1\" or \"0\"\n" + "else\n" + "    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 then\n" + "    return \"0\"\n" + "end\n" + "local storedSecret = redis.call(\"get\", lockKey)\n" + "if storedSecret == lockSecret then\n" + "    local result = redis.call(\"expire\", lockKey, expireTime)\n" + "    return result == 1 and \"1\" or \"0\"\n" + "else\n" + "    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 執(zhí)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(); // 移除已經(jīng)釋放的鎖
                        }
                    }
                }
            } catch (Exception e) {
                System.err.println("看門狗任務(wù)執(zhí)行失敗: " + 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 配置類

@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 RedisUtils redisUtils;


    @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;
    }

}

后記

還是免責(zé)聲明，僅供學(xué)習(xí)參考

posted @ 2025-03-13 21:55 帥氣的濤啊閱讀(485) 評(píng)論(1) 收藏舉報(bào)

刷新頁面返回頂部

次日清晨醒著眼睛

我寫的代碼和詩一樣

學(xué)習(xí)高可靠Redis分布式鎖實(shí)現(xiàn)思路

一、分布式鎖的必要性

二、核心實(shí)現(xiàn)解析（附源碼）

2.1 原子性加鎖

2.2 看門狗續(xù)期機(jī)制

2.3 安全釋放鎖

三、源碼

四、如何使用

4.1 配置類

4.2 使用

后記

公告

次日清晨醒著眼睛

我寫的代碼和詩一樣

學(xué)習(xí)高可靠Redis分布式鎖實(shí)現(xiàn)思路

一、分布式鎖的必要性

二、核心實(shí)現(xiàn)解析（附源碼）

2.1 原子性加鎖

2.2 看門狗續(xù)期機(jī)制

2.3 安全釋放鎖

三、源碼

四、如何使用

4.1 配置類

4.2 使用

后記

公告

一、分布式鎖的必要性

二、核心實(shí)現(xiàn)解析（附源碼）

三、源碼

四、如何使用