Using Laravel's RedisLock to Prevent Cache Breakdown

Cache breakdown occurs when a cached item expires, many concurrent requests miss the cache, and simultaneously query the database, causing a sudden spike in database load.

Using a Redis lock is an effective way to mitigate this issue. Laravel 7 includes the \Illuminate\Cache\RedisLock class, which can be instantiated directly.

The constructor of RedisLock is defined as:

/**
 * @param \Illuminate\Redis\Connections\Connection $redis redis instance
 * @param string $name redis lock key name
 * @param int $seconds redis lock expiration time
 * @param string|null $owner redis lock value; if null, a random string is generated
 */
public function __construct($redis, $name, $seconds, $owner = null)
{
    parent::__construct($name, $seconds, $owner);
    $this->redis = $redis;
}

After creating a RedisLock object, you can call acquire() to obtain an exclusive lock and release() to free it.

Example usage:

use Illuminate\Support\Facades\Redis;
use Illuminate\Cache\RedisLock;

function RedisLockTest()
{
    // Get Redis instance
    $redis = Redis::connection();
    $key = 'redis_test_key';
    // Create RedisLock instance
    $redisLock = new RedisLock($redis, $key . '_lock', 30);
    $res = $redis->get($key);
    if (empty($res)) {
        // Try to acquire lock
        if ($redisLock->acquire()) {
            // Simulate fetching data from database
            sleep(5);
            $value = date('Y-m-d H:i:s');
            // Update cache (expire in 60 seconds)
            $redis->setex($key, 60, $value);
            // Release lock
            $redisLock->release();
            return $value;
        } else {
            // Wait and retry
            sleep(2);
            return RedisLockTest();
        }
    } else {
        return $res;
    }
}

This pattern ensures that only one request populates the cache while others wait, preventing the database from being overwhelmed during high concurrency scenarios.