Redis利用互斥锁解决缓存击穿问题

<dependency>
    <groupId>redis.clients</groupId>
    <artifactId>jedis</artifactId>
    <version>3.7.0</version>
</dependency>

import redis.clients.jedis.Jedis;
import java.util.concurrent.TimeUnit;

public class CacheBustingMutex {

    private static final String REDIS_HOST = "localhost";
    private static final int REDIS_PORT = 6379;
    private static final String LOCK_KEY = "lock:cache-busting";

    public Object getDataFromCacheOrDB(String key) {
        Jedis jedis = new Jedis(REDIS_HOST, REDIS_PORT);
        try {
            // Step 1: Try to get data from cache
            String cachedData = jedis.get(key);
            if (cachedData != null) {
                return cachedData;
            }

            // Step 2: Try to acquire the lock
            if (!acquireLock(jedis)) {
                // Lock not acquired, sleep and retry
                TimeUnit.MILLISECONDS.sleep(50);
                return getDataFromCacheOrDB(key); // Retry
            }

            try {
                // Step 3: Data not in cache, query DB
                String dbData = queryDatabase(key);

                // Step 4: Update cache
                jedis.setex(key, 300, dbData); // Set cache with TTL of 5 minutes

                return dbData;
            } finally {
                // Step 5: Release lock
                releaseLock(jedis);
            }
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
            throw new RuntimeException("Interrupted while sleeping", e);
        } finally {
            jedis.close();
        }
    }

    private boolean acquireLock(Jedis jedis) {
        // Use SETNX (SET if Not eXists) to acquire lock
        return "OK".equals(jedis.set(LOCK_KEY, "locked", "NX", "EX", 5));
    }

    private void releaseLock(Jedis jedis) {
        // Use Lua script to safely release the lock
        String luaScript = "if redis.call('get', KEYS[1]) == ARGV[1] then return redis.call('del', KEYS[1]) else return 0 end";
        Object result = jedis.eval（luaScript, Collections.singletonList(LOCK_KEY), Collections.singletonList("locked"));
        // Check if the lock was released
        if (!(Boolean) result) {
            System.out.println("Failed to release lock.");
        }
    }

    private String queryDatabase(String key) {
        // Simulate querying the database
        return "Data for " + key;
    }
}