package com.kidgrow.redis.lock;
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import com.kidgrow.common.lock.AbstractDistributedLock;
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import lombok.extern.slf4j.Slf4j;
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import org.springframework.beans.factory.annotation.Autowired;
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import org.springframework.data.redis.connection.RedisStringCommands;
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import org.springframework.data.redis.connection.ReturnType;
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import org.springframework.data.redis.core.RedisCallback;
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import org.springframework.data.redis.core.RedisTemplate;
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import org.springframework.data.redis.core.types.Expiration;
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import org.springframework.stereotype.Component;
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import java.util.UUID;
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import java.util.concurrent.TimeUnit;
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/**
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* 石家庄喜高科技有限责任公司 版权所有 © Copyright 2020<br>
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*
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* @Description: Redis分布式锁实现<br>
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* @Project: <br>
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* @CreateDate: Created in 2020/2/4 16:05 <br>
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* @Author: <a href="4345453@kidgrow.com">liuke</a>
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*/
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@Slf4j
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@Component
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public class RedisDistributedLock extends AbstractDistributedLock {
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@Autowired
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private RedisTemplate<String, Object> redisTemplate;
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private ThreadLocal<String> lockFlag = new ThreadLocal<>();
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private static final String UNLOCK_LUA;
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/*
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* 通过lua脚本释放锁,来达到释放锁的原子操作
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*/
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static {
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UNLOCK_LUA = "if redis.call(\"get\",KEYS[1]) == ARGV[1] " +
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"then " +
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" return redis.call(\"del\",KEYS[1]) " +
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"else " +
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" return 0 " +
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"end ";
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}
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public RedisDistributedLock(RedisTemplate<String, Object> redisTemplate) {
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super();
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this.redisTemplate = redisTemplate;
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}
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@Override
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public boolean lock(String key, long expire, int retryTimes, long sleepMillis) {
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boolean result = setRedis(key, expire);
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// 如果获取锁失败，按照传入的重试次数进行重试
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while ((!result) && retryTimes-- > 0) {
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try {
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log.debug("get redisDistributeLock failed, retrying..." + retryTimes);
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Thread.sleep(sleepMillis);
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} catch (InterruptedException e) {
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log.warn("Interrupted!", e);
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Thread.currentThread().interrupt();
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}
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result = setRedis(key, expire);
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}
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return result;
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}
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private boolean setRedis(final String key, final long expire) {
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try {
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boolean status = redisTemplate.execute((RedisCallback<Boolean>) connection -> {
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String uuid = UUID.randomUUID().toString();
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lockFlag.set(uuid);
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byte[] keyByte = redisTemplate.getStringSerializer().serialize(key);
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byte[] uuidByte = redisTemplate.getStringSerializer().serialize(uuid);
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boolean result = connection.set(keyByte, uuidByte, Expiration.from(expire, TimeUnit.MILLISECONDS), RedisStringCommands.SetOption.ifAbsent());
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return result;
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});
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return status;
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} catch (Exception e) {
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log.error("set redisDistributeLock occured an exception", e);
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}
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return false;
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}
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@Override
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public boolean releaseLock(String key) {
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// 释放锁的时候，有可能因为持锁之后方法执行时间大于锁的有效期，此时有可能已经被另外一个线程持有锁，所以不能直接删除
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try {
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// 使用lua脚本删除redis中匹配value的key，可以避免由于方法执行时间过长而redis锁自动过期失效的时候误删其他线程的锁
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// spring自带的执行脚本方法中，集群模式直接抛出不支持执行脚本的异常，所以只能拿到原redis的connection来执行脚本
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Boolean result = redisTemplate.execute((RedisCallback<Boolean>) connection -> {
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byte[] scriptByte = redisTemplate.getStringSerializer().serialize(UNLOCK_LUA);
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return connection.eval(scriptByte, ReturnType.BOOLEAN, 1
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, redisTemplate.getStringSerializer().serialize(key)
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, redisTemplate.getStringSerializer().serialize(lockFlag.get()));
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});
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return result;
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} catch (Exception e) {
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log.error("release redisDistributeLock occured an exception", e);
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} finally {
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lockFlag.remove();
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}
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return false;
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}
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}
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