Redis 分布式锁解决方案是一种基于Redis实现的分布式锁机制,可以确保在分布式环境中对共享资源的访问进行同步控制,避免出现竞态条件和数据不一致的问题。在分布式系统中,多个服务之间需要相互协调来访问共享资源,而分布式锁可以提供一个简单而有效的方式来实现这种协调。
public class DistributedLock {
private Jedis jedis;
private String lockKey;
private String requestId;
private int expireTime;
public DistributedLock(Jedis jedis, String lockKey, String requestId, int expireTime) {
this.jedis = jedis;
this.lockKey = lockKey;
this.requestId = requestId;
this.expireTime = expireTime;
}
public boolean tryAcquireLock() {
String result = jedis.set(lockKey, requestId, "NX", "EX", expireTime);
return "OK".equals(result);
}
public boolean releaseLock() {
String storedRequestId = jedis.get(lockKey);
if (requestId.equals(storedRequestId)) {
jedis.del(lockKey);
return true;
} else {
return false;
}
}
}
上面的代码中,tryAcquireLock方法尝试获取分布式锁,如果设置成功,则返回true;如果设置失败,则返回false。releaseLock方法用于释放分布式锁。
public class ReentrantDistributedLock {
private Jedis jedis;
private String lockKey;
private String requestId;
private int expireTime;
private Map acquiredLockMap;
public ReentrantDistributedLock(Jedis jedis, String lockKey, String requestId, int expireTime) {
this.jedis = jedis;
this.lockKey = lockKey;
this.requestId = requestId;
this.expireTime = expireTime;
this.acquiredLockMap = new HashMap< >();
}
public boolean tryAcquireLock() {
Integer acquiredCount = acquiredLockMap.getOrDefault(requestId, 0);
if (acquiredCount > 0) {
acquiredLockMap.put(requestId, acquiredCount + 1);
return true;
} else {
String result = jedis.set(lockKey, requestId, "NX", "EX", expireTime);
if ("OK".equals(result)) {
acquiredLockMap.put(requestId, 1);
return true;
} else {
return false;
}
}
}
public boolean releaseLock() {
Integer acquiredCount = acquiredLockMap.getOrDefault(requestId, 0);
if (acquiredCount == 0) {
return false;
}
acquiredCount--;
if (acquiredCount > 0) {
acquiredLockMap.put(requestId, acquiredCount);
} else {
acquiredLockMap.remove(requestId);
String storedRequestId = jedis.get(lockKey);
if (requestId.equals(storedRequestId)) {
jedis.del(lockKey);
} else {
throw new IllegalStateException("Lock has been acquired by other requestId");
}
}
return true;
}
}
上面的代码中,acquiredLockMap用于记录每个requestId获取锁的次数,tryAcquireLock方法在获取锁时,会检查acquiredLockMap中对应的次数,如果大于0,则表示已经获取了锁,直接返回true;否则,尝试使用SETNX命令来获取锁。releaseLock方法在释放锁时,会根据acquiredLockMap中对应的次数进行操作,在最后一次释放锁时,才真正执行释放操作。
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