Redis+IDEA實(shí)現(xiàn)單機(jī)鎖和分布式鎖的過程

更新時(shí)間：2023年07月14日 09:54:30 作者：kkoneone11

這篇文章主要介紹了Redis+IDEA實(shí)現(xiàn)單機(jī)鎖和分布式鎖的過程,本文通過示例代碼給大家介紹的非常詳細(xì)，對(duì)大家的學(xué)習(xí)或工作具有一定的參考借鑒價(jià)值，需要的朋友可以參考下

單機(jī)下：

只適用于單機(jī)環(huán)境下（單個(gè)JVM），多個(gè)客戶端訪問同一個(gè)服務(wù)器

1.synchronized

package com.cloud.SR.controller;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import javax.annotation.Resource;
@RestController
public class TestConrtoller1 {
    @Value("${server.port}")
    private String serverPort;
    @Resource
    private StringRedisTemplate stringRedisTemplate;
    @GetMapping("/buy1")
    public String shopping(){
        synchronized (this){
            String result = stringRedisTemplate.opsForValue().get("goods:001");
            int total = result == null? 0 :Integer.parseInt(s);
            if(total > 0){
                int realTotal = total - 1;
                stringRedisTemplate.opsForValue().set("goods:001",String.valueOf(realCount ));
                System.out.println("剩余商品為："+realCount +",提供服務(wù)的端口號(hào)："+serverPort);
                return "剩余商品為："+realTotal +",提供服務(wù)的端口號(hào)："+serverPort;
            }else{
                System.out.println("購(gòu)買商品失??！");
            }
            return "購(gòu)買商品失敗！";
        }
    }
}

2.ReentrantLock

@RestController
public class TestConrtoller2 {
    @Value("${server.port}")
    private String serverPort;
    // 使用ReentrantLock鎖解決單體應(yīng)用的并發(fā)問題
    Lock lock = new ReentrantLock();
    @Autowired
    StringRedisTemplate stringRedisTemplate;
    @RequestMapping("/buy2")
    public String index() {
        lock.lock();
        try {
            String result = stringRedisTemplate.opsForValue().get("goods:001");
            int total = result == null ? 0 : Integer.parseInt(result);
            if (total > 0) {
                int realTotal = total - 1;
                stringRedisTemplate.opsForValue().set("goods:001", String.valueOf(realTotal));
                System.out.println("購(gòu)買商品成功，庫(kù)存還剩：" + realTotal + "，服務(wù)端口為:"+serverPort);
                return "購(gòu)買商品成功，庫(kù)存還剩：" + realTotal + "，服務(wù)端口為："+serverPort;
            } else {
                System.out.println("購(gòu)買商品失?。?);
            }
        } catch (Exception e) {
            lock.unlock();
        } finally {
            lock.unlock();
        }
        return "購(gòu)買商品失??！";
    }
}

分布式下：

而在服務(wù)器分布式集群下，，單個(gè)服務(wù)器的synchronized和ReentrantLock

1.SETNX

SET key value [EX seconds] [PX milliseconds] [NX|XX]

EX seconds – 設(shè)置鍵key的過期時(shí)間，單位時(shí)秒
PX milliseconds – 設(shè)置鍵key的過期時(shí)間，單位時(shí)毫秒
NX – 只有鍵key不存在的時(shí)候才會(huì)設(shè)置key的值
XX – 只有鍵key存在的時(shí)候才會(huì)設(shè)置key的值

例子：

1.set lock01 01 NX ：意思就是說只要誰把key為lock01的值設(shè)置為01且key不存在的時(shí)候就能拿到鎖

2. set lock01 01 NX EX 30 ：在例1的基礎(chǔ)上把鎖設(shè)置的時(shí)間設(shè)置為30秒后過期。避免有服務(wù)掛了而沒有釋放鎖的情況、或者業(yè)務(wù)處理完但一直拿著鎖不釋放導(dǎo)致死鎖。

項(xiàng)目中使用SETNX：

template.opsForValue().setIfAbsent()

測(cè)試的話就得本機(jī)模擬集群，當(dāng)然有虛擬機(jī)的也可以用兩臺(tái)虛擬機(jī)，但此處用兩臺(tái)JVM即可完成簡(jiǎn)易集群本機(jī)實(shí)現(xiàn)集群的可以看這篇文章：http://t.csdn.cn/jvZFx

先讓集群跑起來，然后啟動(dòng)Nginx，再通過Jmeter實(shí)現(xiàn)高并發(fā)的秒殺環(huán)節(jié)

用template.opsForValue().setIfAbsent()命令進(jìn)行加鎖。加上了過期時(shí)間后就解決了key無法刪除的問題，但如果key設(shè)置的時(shí)間太短，當(dāng)業(yè)務(wù)處理的時(shí)間長(zhǎng)于key設(shè)置的時(shí)間，key過期后其他請(qǐng)求就可以設(shè)置這個(gè)key而當(dāng)這個(gè)線程再回來處理這個(gè)程序的時(shí)候就會(huì)把人家設(shè)置的key給刪除了，因此我們規(guī)定誰設(shè)置的鎖只能由誰刪除。

finally {
            // 誰加的鎖，誰才能刪除
            if(template.opsForValue().get(REDIS_LOCK).equals(value)){
                template.delete(REDIS_LOCK);
            }

而新的問題就是finally塊的判斷和del刪除操作不是原子操作，并發(fā)的時(shí)候也會(huì)出問題。因此采用lua（原子性）來進(jìn)行刪除

finally {
            // 誰加的鎖，誰才能刪除，使用Lua腳本，進(jìn)行鎖的刪除
            Jedis jedis = null;
            try{
                jedis = RedisUtils.getJedis();
                String script = "if redis.call('get',KEYS[1]) == ARGV[1] " +
                        "then " +
                        "return redis.call('del',KEYS[1]) " +
                        "else " +
                        "   return 0 " +
                        "end";
                Object eval = jedis.eval(script, Collections.singletonList(REDIS_LOCK), Collections.singletonList(value));
                if("1".equals(eval.toString())){
                    System.out.println("-----del redis lock ok....");
                }else{
                    System.out.println("-----del redis lock error ....");
                }
            }catch (Exception e){
            }finally {
                if(null != jedis){
                    jedis.close();
                }
            }

總的代碼：

@RestController
public class TestConrtoller3 {
    @Value("${server.port}")
    private String serverPort;
    public static final String REDIS_LOCK = "good_lock";
    @Autowired
    StringRedisTemplate stringtemplate;
    @RequestMapping("/buy3")
    public String shopping(){
        // 每個(gè)人進(jìn)來先要進(jìn)行加鎖，key值為"good_lock",且用UUID保證每個(gè)人的鎖不同
        String value = UUID.randomUUID().toString().replace("-","");
        try{
            // 為key加一個(gè)過期時(shí)間
            Boolean flag = stringtemplate.opsForValue().setIfAbsent(REDIS_LOCK, value,10L,TimeUnit.SECONDS);
            // 加鎖失敗
            if(!flag){
                return "搶鎖失?。?;
            }
            System.out.println( value+ " 搶鎖成功");
            String result = stringtemplate.opsForValue().get("goods:001");
            int total = result == null ? 0 : Integer.parseInt(result);
            if (total > 0) {
                // 如果在此處需要調(diào)用其他微服務(wù)，處理時(shí)間較長(zhǎng)。。。
                int realTotal = total - 1;
                stringtemplate.opsForValue().set("goods:001", String.valueOf(realTotal));
                System.out.println("購(gòu)買商品成功，庫(kù)存還剩：" + realTotal + "，服務(wù)端口為"+serverPort);
                return "購(gòu)買商品成功，庫(kù)存還剩：" + realTotal + "服務(wù)端口為"+serverPort;
            } else {
                System.out.println("購(gòu)買商品失敗");
            }
            return "購(gòu)買商品失?。?;
        }finally {
            // 誰加的鎖，誰才能刪除，使用Lua腳本，進(jìn)行鎖的刪除
            Jedis jedis = null;
            try{
                jedis = RedisUtils.getJedis();
                String script = "if redis.call('get',KEYS[1]) == ARGV[1] " +
                        "then " +
                        "return redis.call('del',KEYS[1]) " +
                        "else " +
                        "   return 0 " +
                        "end";
                Object eval = jedis.eval(script, Collections.singletonList(REDIS_LOCK), Collections.singletonList(value));
                if("1".equals(eval.toString())){
                    System.out.println("-----del redis lock ok....");
                }else{
                    System.out.println("-----del redis lock error ....");
                }
            }catch (Exception e){
            }finally {
                if(null != jedis){
                    jedis.close();
                }
            }
        }
    }
}

2.Redisson(推薦)

考慮緩存續(xù)命，以及Redis集群部署下，異步復(fù)制造成的鎖丟失：主節(jié)點(diǎn)沒來得及把剛剛set進(jìn)來這條數(shù)據(jù)給從節(jié)點(diǎn)，就掛了。所以直接上RedLock的Redisson落地實(shí)現(xiàn)

@RestController
public class TestConrtoller4 {
    @Value("${server.port}")
    private String serverPort;
    public static final String REDIS_LOCK = "good_lock";
    @Autowired
    StringRedisTemplate stringtemplate;
    @Autowired
    Redisson redisson;
    @RequestMapping("/buy4")
    public String shopping(){
        RLock lock = redisson.getLock(REDIS_LOCK);
        lock.lock();
        // 每個(gè)人進(jìn)來先要進(jìn)行加鎖，key值為"good_lock"
        String value = UUID.randomUUID().toString().replace("-","");
        try{
            String result = stringtemplate.opsForValue().get("goods:001");
            int total = result == null ? 0 : Integer.parseInt(result);
            if (total > 0) {
                // 如果在此處需要調(diào)用其他微服務(wù)，處理時(shí)間較長(zhǎng)
                int realTotal = total - 1;
                stringtemplate.opsForValue().set("goods:001", String.valueOf(realTotal));
                System.out.println("購(gòu)買商品成功，庫(kù)存還剩：" + realTotal + "件， 服務(wù)端口為"+serverPort);
                return "購(gòu)買商品成功，庫(kù)存還剩：" + realTotal + "件， 服務(wù)端口為"+serverPort;
            } else {
                System.out.println("購(gòu)買商品失敗");
            }
            return "購(gòu)買商品失敗";
        }finally {
            if(lock.isLocked() && lock.isHeldByCurrentThread()){
                lock.unlock();
            }
        }
    }
}

Redis工具類

 
import com.myfutech.common.util.constant.RedisPrefix;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.connection.RedisStringCommands;
import org.springframework.data.redis.connection.ReturnType;
import org.springframework.data.redis.core.RedisCallback;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.types.Expiration;
import java.nio.charset.StandardCharsets;
import java.util.UUID;
/**
 * 基于redis分布式鎖
 */
@Slf4j
public class RedisLockUtils {
    /**
     * 默認(rèn)輪休獲取鎖間隔時(shí)間， 單位：毫秒
     */
    private static final int DEFAULT_ACQUIRE_RESOLUTION_MILLIS = 100;
    private static final String UNLOCK_LUA;
    static {
        StringBuilder sb = new StringBuilder();
        sb.append("if redis.call(\"get\",KEYS[1]) == ARGV[1] ");
        sb.append("then ");
        sb.append("    return redis.call(\"del\",KEYS[1]) ");
        sb.append("else ");
        sb.append("    return 0 ");
        sb.append("end ");
        UNLOCK_LUA = sb.toString();
    }
    /**
     * 獲取鎖，沒有獲取到則一直等待，異常情況則返回null
     *
     * @param redisTemplate     redis連接
     * @param key               redis key
     * @param expire            鎖過期時(shí)間, 單位 秒
     * @return                  當(dāng)前鎖唯一id，如果沒有獲取到，返回 null
     */
    public static String lock(RedisTemplate redisTemplate, final String key, long expire){
        return lock(redisTemplate, key, expire, -1);
    }
    /**
     * 獲取鎖，acquireTimeout時(shí)間內(nèi)沒有獲取到，則返回null，異常情況返回null
     *
     * @param redisTemplate     redis連接
     * @param key               redis key
     * @param expire            鎖過期時(shí)間, 單位 秒
     * @param acquireTimeout    獲取鎖超時(shí)時(shí)間, -1代表永不超時(shí), 單位 秒
     * @return                  當(dāng)前鎖唯一id，如果沒有獲取到，返回 null
     */
    public static String lock(RedisTemplate redisTemplate, final String key, long expire, long acquireTimeout){
        try {
            return acquireLock(redisTemplate, key, expire, acquireTimeout);
        } catch (Exception e) {
            log.error("acquire lock exception", e);
        }
        return null;
    }
    /**
     * 獲取鎖，沒有獲取到則一直等待，沒有獲取到則拋出異常
     *
     * @param redisTemplate     redis連接
     * @param key               redis key
     * @param expire            鎖過期時(shí)間, 單位 秒
     * @return                  當(dāng)前鎖唯一id，如果沒有獲取到，返回 null
     */
    public static String lockFailThrowException(RedisTemplate redisTemplate, final String key, long expire){
        return lockFailThrowException(redisTemplate, key, expire, -1);
    }
    /**
     * 獲取鎖，到達(dá)超時(shí)時(shí)間時(shí)沒有獲取到，則拋出異常
     *
     * @param redisTemplate     redis連接
     * @param key               redis key
     * @param expire            鎖過期時(shí)間, 單位 秒
     * @param acquireTimeout    獲取鎖超時(shí)時(shí)間, -1代表永不超時(shí), 單位 秒
     * @return                  當(dāng)前鎖唯一id，如果沒有獲取到，返回 null
     */
    public static String lockFailThrowException(RedisTemplate redisTemplate, final String key, long expire, long acquireTimeout){
        try {
            String lockId = acquireLock(redisTemplate, key, expire, acquireTimeout);
            if (lockId != null) {
                return lockId;
            }
            throw new RuntimeException("acquire lock fail");
        } catch (Exception e) {
            throw new RuntimeException("acquire lock exception", e);
        }
    }
    private static String acquireLock(RedisTemplate redisTemplate, String key, long expire, long acquireTimeout) throws InterruptedException {
        long acquireTime = -1;
        if (acquireTimeout != -1) {
            acquireTime = acquireTimeout * 1000 + System.currentTimeMillis();
        }
        synchronized (key) {
            String lockId = UUID.randomUUID().toString();
            while (true) {
                if (acquireTime != -1 && acquireTime < System.currentTimeMillis()) {
                    break;
                }
                //調(diào)用tryLock
                boolean hasLock = tryLock(redisTemplate, key, expire, lockId);
                //獲取鎖成功
                if (hasLock) {
                    return lockId;
                }
                Thread.sleep(DEFAULT_ACQUIRE_RESOLUTION_MILLIS);
            }
        }
        return null;
    }
    /**
     *  釋放鎖
     *
     * @param redisTemplate     redis連接
     * @param key               redis key
     * @param lockId            當(dāng)前鎖唯一id
     */
    public static void unlock(RedisTemplate redisTemplate, String key, String lockId) {
        try {
            RedisCallback<Boolean> callback = (connection) ->
                    connection.eval(UNLOCK_LUA.getBytes(StandardCharsets.UTF_8),ReturnType.BOOLEAN, 1,
                            (RedisPrefix.LOCK_REDIS_PREFIX + key).getBytes(StandardCharsets.UTF_8), lockId.getBytes(StandardCharsets.UTF_8));
            redisTemplate.execute(callback);
        } catch (Exception e) {
            log.error("release lock exception", e);
        }
    }
    /**
     * 獲取當(dāng)前鎖的id
     *
     * @param key       redis key
     * @return          當(dāng)前鎖唯一id
     */
    public static String get(RedisTemplate redisTemplate, String key) {
        try {
            RedisCallback<String> callback = (connection) -> {
                byte[] bytes = connection.get((RedisPrefix.LOCK_REDIS_PREFIX + key).getBytes(StandardCharsets.UTF_8));
                if (bytes != null){
                    return new String(bytes, StandardCharsets.UTF_8);
                }
                return null;
            };
            return (String)redisTemplate.execute(callback);
        } catch (Exception e) {
            log.error("get lock id exception", e);
        }
        return null;
    }
    private static boolean tryLock(RedisTemplate redisTemplate, String key, long expire, String lockId) {
        RedisCallback<Boolean> callback = (connection) ->
        connection.set((RedisPrefix.LOCK_REDIS_PREFIX + key).getBytes(StandardCharsets.UTF_8),
                lockId.getBytes(StandardCharsets.UTF_8), Expiration.seconds(expire), RedisStringCommands.SetOption.SET_IF_ABSENT);
        return (Boolean)redisTemplate.execute(callback);
    }
}

到此這篇關(guān)于Redis+IDEA極速了解和實(shí)現(xiàn)單機(jī)鎖和分布式鎖的文章就介紹到這了,更多相關(guān)Redis單機(jī)鎖和分布式鎖內(nèi)容請(qǐng)搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關(guān)文章希望大家以后多多支持腳本之家！

您可能感興趣的文章: