redisson是如何处理的？
redisson给的答案是锁获取成功后，注册一个定时任务，每隔一定时间(this.internalLockLeaseTime / 3L)就去续约。internalLockLeaseTime可配置，默认30s。这种方式每次获取一个锁，就会创建一个定时任务，有些浪费。
我的处理
这里给出了一种方式，借鉴jvm对自旋锁优化的思想（根据历史耗时动态调整锁的过期时间），将续约的key的耗时保存在redis，再次获取锁时，直接使用上次耗时 + 10s 作为锁的过期时间， 不用每次都去续约。缺点：获取锁后->释放锁前，若每次执行耗时差距过大（业务方法的各条流程耗时差距过大），将得不到预期的效果。
pom.xml如下：
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.data</groupId>
<artifactId>spring-data-redis</artifactId>
<version>2.1.10.RELEASE</version>
</dependency>
<dependency>
<groupId>io.lettuce</groupId>
<artifactId>lettuce-core</artifactId>
<version>5.1.8.RELEASE</version>
</dependency>
<dependencies>
代码如下：
package com.example.core;
import lombok.Data;
import lombok.ToString;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.RedisCallback;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.core.script.RedisScript;
import org.springframework.stereotype.Service;
import java.io.Serializable;
import java.util.*;
import java.util.concurrent.*;
/**
* redis分布式锁
* redis分布式锁过期时间到了，但业务还没执行完，怎么办？
* redisson给的答案是锁获取成功后，注册一个定时任务，每隔一定时间(this.internalLockLeaseTime / 3L)就去续约。
* internalLockLeaseTime可配置，默认30s。
* 这种方式每次获取一个锁，就会创建一个定时任务，有些浪费
* 这里借鉴jvm对自旋锁优化的思想，将续约的key的耗时保存在redis，再次获取锁时，直接使用上次耗时 + 10s 作为锁的过期时间，
* 不用每次都去续约。
* 缺点：获取锁后->释放锁前，若每次执行耗时差距过大（业务方法的各条流程耗时差距过大），将得不到预期的效果
*
*/
@Slf4j
@Service
public class RedisDistributionLockPlus {
/**
* 加锁超时时间，单位毫秒， 即：加锁时间内执行完操作，如果未完成会有并发现象
*/
private static final long DEFAULT_LOCK_TIMEOUT = 30;
private static final long TIME_SECONDS_FIVE = 5 ;
/**
* 每个key的过期时间 {@link LockContent}
*/
private Map<String, LockContent> lockContentMap = new ConcurrentHashMap<>(512);
/**
* redis执行成功的返回
*/
private static final Long EXEC_SUCCESS = 1L;
/**
* 获取锁lua脚本， k1：获锁key, k2：续约耗时key, arg1:requestId，arg2：超时时间
*/
private static final String LOCK_SCRIPT = "if redis.call('exists', KEYS[2]) == 1 then ARGV[2] = math.floor(redis.call('get', KEYS[2]) + 10) end " +
"if redis.call('exists', KEYS[1]) == 0 then " +
"local t = redis.call('set', KEYS[1], ARGV[1], 'EX', ARGV[2]) " +
"for k, v in pairs(t) do " +
"if v == 'OK' then return tonumber(ARGV[2]) end " +
"end " +
"return 0 end";
/**
* 释放锁lua脚本, k1：获锁key, k2：续约耗时key, arg1:requestId，arg2：业务耗时 arg3: 业务开始设置的timeout
*/
private static final String UNLOCK_SCRIPT = "if redis.call('get', KEYS[1]) == ARGV[1] then " +
"local ctime = tonumber(ARGV[2]) " +
"local biz_timeout = tonumber(ARGV[3]) " +
"if ctime > 0 then " +
"if redis.call('exists', KEYS[2]) == 1 then " +
"local avg_time = redis.call('get', KEYS[2]) " +
"avg_time = (tonumber(avg_time) * 8 + ctime * 2)/10 " +
"if avg_time >= biz_timeout - 5 then redis.call('set', KEYS[2], avg_time, 'EX', 24*60*60) " +
"else redis.call('del', KEYS[2]) end " +
"elseif ctime > biz_timeout -5 then redis.call('set', KEYS[2], ARGV[2], 'EX', 24*60*60) end " +
"end " +
"return redis.call('del', KEYS[1]) " +
"else return 0 end";
/**
* 续约lua脚本
*/
private static final String RENEW_SCRIPT = "if redis.call('get', KEYS[1]) == ARGV[1] then return redis.call('expire', KEYS[1], ARGV[2]) else return 0 end";
private final StringRedisTemplate redisTemplate;
public RedisDistributionLockPlus(StringRedisTemplate redisTemplate) {
this.redisTemplate = redisTemplate;
ScheduleTask task = new ScheduleTask(this, lockContentMap);
// 启动定时任务
ScheduleExecutor.schedule(task, 1, 1, TimeUnit.SECONDS);
}
/**
* 加锁
* 取到锁加锁，取不到锁一直等待知道获得锁
*
* @param lockKey
* @param requestId 全局唯一
* @param expire 锁过期时间, 单位秒
* @return
*/
public boolean lock(String lockKey, String requestId, long expire) {
log.info("开始执行加锁, lockKey ={}, requestId={}", lockKey, requestId);
for (; ; ) {
// 判断是否已经有线程持有锁，减少redis的压力
LockContent lockContentOld = lockContentMap.get(lockKey);
boolean unLocked = null == lockContentOld;
// 如果没有被锁，就获取锁
if (unLocked) {
long startTime = System.currentTimeMillis();
// 计算超时时间
long bizExpire = expire == 0L DEFAULT_LOCK_TIMEOUT : expire;
String lockKeyRenew = lockKey + "_renew";
RedisScript<Long> script = RedisScript.of(LOCK_SCRIPT, Long.class);
List<String> keys = new ArrayList<>();
keys.add(lockKey);
keys.add(lockKeyRenew);
Long lockExpire = redisTemplate.execute(script, keys, requestId, Long.toString(bizExpire));
if (null != lockExpire && lockExpire > 0) {
// 将锁放入map
LockContent lockContent = new LockContent();
lockContent.setStartTime(startTime);
lockContent.setLockExpire(lockExpire);
lockContent.setExpireTime(startTime + lockExpire * 1000);
lockContent.setRequestId(requestId);
lockContent.setThread(Thread.currentThread());
lockContent.setBizExpire(bizExpire);
lockContent.setLockCount(1);
lockContentMap.put(lockKey, lockContent);
log.info("加锁成功, lockKey ={}, requestId={}", lockKey, requestId);
return true;
}
}
// 重复获取锁，在线程池中由于线程复用，线程相等并不能确定是该线程的锁
if (Thread.currentThread() == lockContentOld.getThread()
&& requestId.equals(lockContentOld.getRequestId())){
// 计数 +1
lockContentOld.setLockCount(lockContentOld.getLockCount()+1);
return true;
}
// 如果被锁或获取锁失败，则等待100毫秒
try {
TimeUnit.MILLISECONDS.sleep(100);
} catch (InterruptedException e) {
// 这里用lombok 有问题
log.error("获取redis 锁失败, lockKey ={}, requestId={}", lockKey, requestId, e);
return false;
}
}
}
/**
* 解锁
*
* @param lockKey
* @param lockValue
*/
public boolean unlock(String lockKey, String lockValue) {
String lockKeyRenew = lockKey + "_renew";
LockContent lockContent = lockContentMap.get(lockKey);
long consumeTime;
if (null == lockContent) {
consumeTime = 0L;
} else if (lockValue.equals(lockContent.getRequestId())) {
int lockCount = lockContent.getLockCount();
// 每次释放锁， 计数 -1，减到0时删除redis上的key
if (--lockCount > 0) {
lockContent.setLockCount(lockCount);
return false;
}
consumeTime = (System.currentTimeMillis() - lockContent.getStartTime()) / 1000;
} else {
log.info("释放锁失败，不是自己的锁。");
return false;
}
// 删除已完成key，先删除本地缓存，减少redis压力, 分布式锁，只有一个，所以这里不加锁
lockContentMap.remove(lockKey);
RedisScript<Long> script = RedisScript.of(UNLOCK_SCRIPT, Long.class);
List<String> keys = new ArrayList<>();
keys.add(lockKey);
keys.add(lockKeyRenew);
Long result = redisTemplate.execute(script, keys, lockValue, Long.toString(consumeTime),
Long.toString(lockContent.getBizExpire()));
return EXEC_SUCCESS.equals(result);
}
/**
* 多服务器集群，使用下面的方法，代替System.currentTimeMillis()，获取redis时间，避免多服务的时间不一致问题！！！
*
* @return
*/
public long currtTimeForRedis() {
return redisTemplate.execute((RedisCallback<Long>) redisConnection -> redisConnection.time());
}
/**
* 续约
*
* @param lockKey
* @param lockContent
* @return true:续约成功，false:续约失败（1、续约期间执行完成，锁被释放 2、不是自己的锁，3、续约期间锁过期了（未解决））
*/
public boolean renew(String lockKey, LockContent lockContent) {
// 检测执行业务线程的状态
Thread.State state = lockContent.getThread().getState();
if (Thread.State.TERMINATED == state) {
log.info("执行业务的线程已终止,不再续约 lockKey ={}, lockContent={}", lockKey, lockContent);
return false;
}
String requestId = lockContent.getRequestId();
long timeOut = (lockContent.getExpireTime() - lockContent.getStartTime()) / 1000;
RedisScript<Long> script = RedisScript.of(RENEW_SCRIPT, Long.class);
List<String> keys = new ArrayList<>();
keys.add(lockKey);
Long result = redisTemplate.execute(script, keys, requestId, Long.toString(timeOut));
log.info("续约结果，True成功，False失败 lockKey ={}, result={}", lockKey, EXEC_SUCCESS.equals(result));
return EXEC_SUCCESS.equals(result);
}
static class ScheduleExecutor {
public static void schedule(ScheduleTask task, long initialDelay, long period, TimeUnit unit) {
long delay = unit.toMillis(initialDelay);
long period_ = unit.toMillis(period);
// 定时执行
new Timer("Lock-Renew-Task").schedule(task, delay, period_);
}
}
static class ScheduleTask extends TimerTask {
private final RedisDistributionLockPlus redisDistributionLock;
private final Map<String, LockContent> lockContentMap;
public ScheduleTask(RedisDistributionLockPlus redisDistributionLock, Map<String, LockContent> lockContentMap) {
this.redisDistributionLock = redisDistributionLock;
this.lockContentMap = lockContentMap;
}
@Override
public void run() {
if (lockContentMap.isEmpty()) {
return;
}
Set<Map.Entry<String, LockContent>> entries = lockContentMap.entrySet();
for (Map.Entry<String, LockContent> entry : entries) {
String lockKey = entry.getKey();
LockContent lockContent = entry.getValue();
long expireTime = lockContent.getExpireTime();
// 减少线程池中任务数量
if ((expireTime - System.currentTimeMillis())/ 1000 < TIME_SECONDS_FIVE) {
//线程池异步续约
ThreadPool.submit(() -> {
boolean renew = redisDistributionLock.renew(lockKey, lockContent);
if (renew) {
long expireTimeNew = lockContent.getStartTime() + (expireTime - lockContent.getStartTime()) * 2 - TIME_SECONDS_FIVE * 1000;
lockContent.setExpireTime(expireTimeNew);
} else {
// 续约失败，说明已经执行完 OR redis 出现问题
lockContentMap.remove(lockKey);
}
});
}
}
}
}
@Data
@ToString
public static class LockContent implements Serializable {
/**
* 锁过期时间，单位秒
*/
private volatile long lockExpire;
/**
* 锁过期时间，单位毫秒
*/
private volatile long expireTime;
/**
* 获取锁的开始时间，单位毫秒
*/
private volatile long startTime;
/**
* 用于防止锁的误删，全局唯一
*/
private String requestId;
/**
* 执行业务的线程
*/
private volatile Thread thread;
/**
* 业务调用设置的锁过期时间，单位秒
*/
private long bizExpire;
/**
* 重入次数
*/
private int lockCount = 0;
}
static class ThreadPool {
private static final int CORESIZE = Runtime.getRuntime().availableProcessors();
private static final int MAXSIZE = 200;
private static final int KEEPALIVETIME = 60;
private static final int CAPACITY = 2000;
private static ThreadPoolExecutor threadPool;
static {
init();
}
private ThreadPool() {}
/**
* 初始化所有线程池。
*/
private static void init() {
threadPool = new ThreadPoolExecutor(CORESIZE, MAXSIZE, KEEPALIVETIME,
TimeUnit.SECONDS, new LinkedBlockingQueue<>(CAPACITY));
log.info("初始化线程池成功。");
}
public static Future<?> submit(Runnable task) {
if (null == task) {
throw new IllegalArgumentException("任务不能为空");
}
return threadPool.submit(task);
}
}
}