2024软考架构师考试---分布式锁的实现方式有那些以及优缺点

-- 创建锁表
CREATE TABLE `distributed_lock` (
    `resource` VARCHAR(64) NOT NULL PRIMARY KEY,
    `locked` TINYINT(1) NOT NULL DEFAULT 0,
    `owner` VARCHAR(64) NOT NULL
);

-- 获取锁
INSERT INTO distributed_lock (resource, locked, owner) VALUES ('resource_name', 1, 'node_id')
ON DUPLICATE KEY UPDATE locked = IF(locked = 0, 1, locked), owner = IF(locked = 0, 'node_id', owner);

-- 释放锁
UPDATE distributed_lock SET locked = 0 WHERE resource = 'resource_name' AND owner = 'node_id';

import redis.clients.jedis.Jedis;

public class RedisLock {

    private Jedis jedis;
    private String lockKey;
    private long lockTimeout;

    public RedisLock(Jedis jedis, String lockKey, long lockTimeout) {
        this.jedis = jedis;
        this.lockKey = lockKey;
        this.lockTimeout = lockTimeout;
    }

    public boolean tryLock(String value) {
        long end = System.currentTimeMillis() + lockTimeout;
        while (System.currentTimeMillis() < end) {
            if (jedis.setnx(lockKey, value) == 1) {
                jedis.expire(lockKey, (int) (lockTimeout / 1000));
                return true;
            }
            if (jedis.ttl(lockKey) == -1) {
                jedis.expire(lockKey, (int) (lockTimeout / 1000));
            }
            try {
                Thread.sleep(50);
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            }
        }
        return false;
    }

    public void unlock(String value) {
        if (value.equals(jedis.get(lockKey))) {
            jedis.del(lockKey);
        }
    }
}

import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.recipes.locks.InterProcessMutex;

public class ZookeeperLock {

    private InterProcessMutex lock;

    public ZookeeperLock(CuratorFramework client, String lockPath) {
        this.lock = new InterProcessMutex(client, lockPath);
    }

    public void lock() throws Exception {
        lock.acquire();
    }

    public void unlock() throws Exception {
        lock.release();
    }
}

import io.etcd.jetcd.Client;
import io.etcd.jetcd.lock.LockResponse;
import io.etcd.jetcd.options.PutOption;

public class EtcdLock {

    private Client client;
    private String lockKey;
    private long leaseId;

    public EtcdLock(Client client, String lockKey) {
        this.client = client;
        this.lockKey = lockKey;
    }

    public boolean lock() {
        try {
            leaseId = client.getLeaseClient().grant(5).get().getID();
            LockResponse response = client.getLockClient().lock(lockKey.getBytes(), leaseId).get();
            return response != null;
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        }
    }

    public void unlock() {
        try {
            client.getLockClient().unlock(lockKey.getBytes()).get();
            client.getLeaseClient().revoke(leaseId).get();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}