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This article mainly introduces the relevant knowledge of the case analysis of the implementation principle of redis distributed lock, the content is detailed and easy to understand, the operation is simple and fast, and has a certain reference value. I believe you will gain something after reading this article on the implementation principle of redis distributed lock. Let's take a look at it.

First, to ensure that distributed locks are available, we need to ensure that the implementation of the lock meets at least the following four conditions:

1. Repulsion. At any given time, only one client can hold the lock.

two。 There is no deadlock. Even if one client crashes while holding the lock without actively unlocking it, it is guaranteed that other clients will be able to lock it.

3. It is fault tolerant. As long as most of the Redis nodes are functioning properly, the client can lock and unlock.

4. The person who unlocks the bell must also tie the bell. Locking and unlocking must be the same client, and the client cannot unlock the lock added by others.

The following is the code implementation. First, we need to introduce Jedis open source components through Maven and add the following code to the pom.xml file:

Org.springframework.boot spring-boot-starter-data-redis redis.clients jedis 3.1.0

Distributed lock implementation code, DistributedLock.java

Import redis.clients.jedis.Jedis;import redis.clients.jedis.JedisPool;import redis.clients.jedis.JedisPoolConfig;import redis.clients.jedis.Transaction;import redis.clients.jedis.exceptions.JedisException;import java.util.List;import java.util.UUID;/** * @ author swadian * @ date 2022-3-4 * @ Version 1.0 * @ describetion Redis distributed locking principle * / public class DistributedLock {/ / redis connection pool private static JedisPool jedisPool Static {JedisPoolConfig config = new JedisPoolConfig (); / / set the maximum number of connections config.setMaxTotal (200); / / set the maximum number of idle config.setMaxIdle (8); / / set the maximum wait time config.setMaxWaitMillis (1000 * 100) / / whether verification is required when borrow a jedis instance. If true, all jedis instances are available config.setTestOnBorrow (true); jedisPool = new JedisPool (config, "192.168.3.27", 6379, 3000) } / * * Lock * @ param lockName lock key * @ param acquireTimeout gets the timeout of the lock * @ param timeout lock timeout * @ return lock ID * Redis Setnx (SET if Not eXists) command sets the specified value for key when the specified key does not exist. * if the setting is successful, 1 is returned. Setting failed and 0 was returned. * / public String lockWithTimeout (String lockName, long acquireTimeout, long timeout) {Jedis jedis = null; String retIdentifier = null; try {/ / get connection jedis = jedisPool.getResource (); / / value value-> randomly generate a String String identifier = UUID.randomUUID () .toString () / / key value-> that is, lock name String lockKey = "lock:" + lockName; / / timeout-> if the lock exceeds this time, the lock will be automatically released in milliseconds to-> seconds int lockExpire = (int) (timeout / 1000) / / timeout for acquiring locks-> if the timeout exceeds this time, the acquisition lock long end = System.currentTimeMillis () + acquireTimeout; while (System.currentTimeMillis ()) will be abandoned.

< end) { //在获取锁时间内 if (jedis.setnx(lockKey, identifier) == 1) {//关键:设置锁 jedis.expire(lockKey, lockExpire); // 返回value值，用于释放锁时间确认 retIdentifier = identifier; return retIdentifier; } // ttl以秒为单位返回 key 的剩余过期时间，返回-1代表key没有设置超时时间，为key设置一个超时时间 if (jedis.ttl(lockKey) == -1) { jedis.expire(lockKey, lockExpire); } try { Thread.sleep(10); } catch (InterruptedException e) { Thread.currentThread().interrupt(); } } } catch (JedisException e) { e.printStackTrace(); } finally { if (jedis != null) { jedis.close(); } } return retIdentifier; } /** * 释放锁 * @param lockName 锁的key * @param identifier 释放锁的标识 * @return */ public boolean releaseLock(String lockName, String identifier) { Jedis jedis = null; String lockKey = "lock:" + lockName; boolean retFlag = false; try { jedis = jedisPool.getResource(); while (true) { // 监视lock，准备开始redis事务 jedis.watch(lockKey); // 通过前面返回的value值判断是不是该锁，若是该锁，则删除，释放锁 if (identifier.equals(jedis.get(lockKey))) { Transaction transaction = jedis.multi();//开启redis事务 transaction.del(lockKey); List results = transaction.exec();//提交redis事务 if (results == null) {//提交失败 continue;//继续循环 } retFlag = true;//提交成功 } jedis.unwatch();//解除监控 break; } } catch (JedisException e) { e.printStackTrace(); } finally { if (jedis != null) { jedis.close(); } } return retFlag; }} 为了验证它，我们创建SkillService.java业务类 import lombok.extern.slf4j.Slf4j;@Slf4jpublic class SkillService { final DistributedLock lock = new DistributedLock(); public static final String LOCK_KEY = "lock_resource"; int n = 500; /** * 线程业务方法 */ public void seckill() { // 返回锁的value值，供释放锁时候进行判断 String identifier = lock.lockWithTimeout(LOCK_KEY, 5000, 1000); log.info("线程:"+Thread.currentThread().getName() + "获得了锁"); log.info("剩余数量:{}",--n); lock.releaseLock(LOCK_KEY, identifier); }} 如果找不到@Slf4j日志，在pom.xml文件加入下面的代码： org.projectlombok lombok 编辑一个测试类TestLock.java /** * @author swadian * @date 2022/3/4 * @Version 1.0 */public class TestLock { public static void main(String[] args) { SkillService service = new SkillService(); for (int i = 10; i < 60; i++) { //开50个线程 SkillThread skillThread = new SkillThread(service, "skillThread->

"+ I); skillThread.start ();} class SkillThread extends Thread {private SkillService skillService; public SkillThread (SkillService skillService, String skillThreadName) {super (skillThreadName); this.skillService = skillService;} @ Override public void run () {skillService.seckill ();}}

The test results show that the remaining quantities after locking are all sequential, 499498497.

We modify the SkillService.java business class to comment out the locking logic

@ Slf4jpublic class SkillService {final DistributedLock lock = new DistributedLock (); public static final String LOCK_KEY = "lock_resource"; int n = 500; / * * Thread business method * / public void seckill () {/ / returns the value of the lock for judging / / String identifier = lock.lockWithTimeout (LOCK_KEY, 5000, 1000) when releasing the lock Log.info ("thread:" + Thread.currentThread (). GetName () + "acquired lock"); log.info ("remaining quantity: {}",-- n); / / lock.releaseLock (LOCK_KEY, identifier);}}

After re-executing the test and commenting out the locking logic, the remaining quantity is all out of order, 472454452.

This is the end of the article on "example Analysis of the implementation principle of redis distributed Lock". Thank you for reading! I believe you all have a certain understanding of the knowledge of "example Analysis of the implementation principle of redis distributed Lock". If you want to learn more knowledge, you are welcome to follow the industry information channel.

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