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package com.yohoufo.common.lock;
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import com.google.common.collect.Lists;
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import lombok.extern.slf4j.Slf4j;
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import org.springframework.data.redis.core.RedisTemplate;
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import org.springframework.data.redis.core.script.DefaultRedisScript;
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import org.springframework.data.redis.core.script.RedisScript;
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import java.util.Random;
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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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* Redis分布式锁
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* 使用 SET resource-name anystring NX EX max-lock-time 实现
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* <p>
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* 该方案在 Redis 官方 SET 命令页有详细介绍。
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* http://doc.redisfans.com/string/set.html
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* <p>
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* 在介绍该分布式锁设计之前，我们先来看一下在从 Redis 2.6.12 开始 SET 提供的新特性，
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* 命令 SET key value [EX seconds] [PX milliseconds] [NX|XX]，其中：
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* <p>
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* EX seconds — 以秒为单位设置 key 的过期时间；
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* PX milliseconds — 以毫秒为单位设置 key 的过期时间；
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* NX — 将key 的值设为value ，当且仅当key 不存在，等效于 SETNX。
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* XX — 将key 的值设为value ，当且仅当key 存在，等效于 SETEX。
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* <p>
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* 命令 SET resource-name anystring NX EX max-lock-time 是一种在 Redis 中实现锁的简单方法。
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* <p>
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* 客户端执行以上的命令：
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* <p>
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* 如果服务器返回 OK ，那么这个客户端获得锁。
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* 如果服务器返回 NIL ，那么客户端获取锁失败，可以在稍后再重试。
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*/
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@Slf4j
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class DefaultRedisLock implements RedisLock {
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private static final String ACQUIRE_OK = "OK";
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private static final Long RELEASE_OK = 1L;
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private RedisTemplate<String, String> redisTemplate;
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private String key;
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/**
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* 锁的有效时间(s)
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*/
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private long expireTimeMillis;
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/**
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* lua script
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*/
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private String lockValue;
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/**
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* 锁标记
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*/
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private boolean locked;
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final Random random = new Random();
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DefaultRedisLock(Builder builder) {
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this.redisTemplate = builder.redisTemplate;
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this.key = builder.key;
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this.expireTimeMillis = builder.expireTimeMillis;
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}
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public boolean lock() {
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updateLockValue();
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while (true) {
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if (acquire(lockValue, expireTimeMillis)) {
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locked = true;
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return true;
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}
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sleep(10, 50000);
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}
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}
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public boolean lock(long timeout, TimeUnit timeUnit) {
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updateLockValue();
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// 请求锁超时时间，纳秒
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long timeoutNanos = timeUnit.toNanos(timeout);
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// 系统当前时间，纳秒
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long nowNanoTime = System.nanoTime();
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while ((System.nanoTime() - nowNanoTime) < timeoutNanos) {
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if (acquire(lockValue, expireTimeMillis)) {
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locked = true;
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// 上锁成功结束请求
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return true;
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}
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// 每次请求等待一段时间
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sleep(10, 50000);
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}
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return locked;
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}
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public boolean tryLock() {
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updateLockValue();
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locked = acquireOr(lockValue, expireTimeMillis, false);
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return locked;
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}
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public boolean unlock() {
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if (locked) {
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if (releaseOr(lockValue, false)) {
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locked = false;
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return true;
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} else {
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return false;
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}
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}
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return true;
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}
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private boolean acquire(String value, long expireTimeMillis) {
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String script = "return redis.call('SET', KEYS[1], ARGV[1], 'NX', 'PX', ARGV[2]) ";
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RedisScript<String> redisScript = new DefaultRedisScript<>(script, String.class);
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String result = redisTemplate.execute(redisScript, Lists.newArrayList(key), value, String.valueOf(expireTimeMillis));
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if (ACQUIRE_OK.equals(result)) {
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log.info("acquire lock ok, key is {} value is {}", key, value);
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return true;
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} else {
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log.info("acquire lock ko, key is {} value is {}", key, value);
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return false;
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}
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}
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private boolean acquireOr(String value, long expireTimeMillis, boolean defaultValue) {
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try {
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return acquire(value, expireTimeMillis);
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} catch (Exception e) {
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log.info("release lock ko, key is {} value is {}", key, value, e);
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return defaultValue;
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}
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}
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private boolean release(String value) {
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String script = "if redis.call('get', KEYS[1]) == ARGV[1] then return redis.call('del', KEYS[1]) else return 0 end";
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RedisScript<Long> redisScript = new DefaultRedisScript(script, Long.class);
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Long result = redisTemplate.execute(redisScript, Lists.newArrayList(key), value);
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if (RELEASE_OK.equals(result)) {
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log.info("release lock ok, key is {} value is {}", key, value);
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return true;
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} else {
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log.info("release lock ko, key is {} value is {}", key, value);
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return false;
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}
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}
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private boolean releaseOr(String value, boolean defaultValue) {
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try {
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return release(value);
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} catch (Exception e) {
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// try once
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try {
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return release(value);
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} catch (Exception e2) {
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log.info("release lock ko, key is {} value is {}", key, value, e2);
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return defaultValue;
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}
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}
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}
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private void updateLockValue() {
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lockValue = UUID.randomUUID().toString();
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}
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/**
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* 线程等待时间
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*
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* @param millis 毫秒
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* @param nanos 纳秒
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*/
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private void sleep(long millis, int nanos) {
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try {
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Thread.sleep(millis, random.nextInt(nanos));
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} catch (InterruptedException e) {
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log.info("lock {} sleep interrupted ", key, e);
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}
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}
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} |
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\ No newline at end of file |
...
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