How to use caching technology to solve PHP high concurrency processing problems

How to use caching technology to solve the problem of high concurrency processing in PHP

Due to the rapid development of the Internet, today's websites and applications are facing increasingly high concurrent visits. . When a large number of users access a PHP website at the same time, the traditional PHP script execution method may cause server performance to decrease, response time to become longer, and even a crash to occur. In order to solve this problem, we can use caching technology to improve the concurrent processing capabilities of the PHP website.

1. What is caching technology?

Caching technology is to temporarily store some frequently accessed data in high-speed storage media so that it can be quickly provided to the next request, thereby reducing the burden on the database and server and improving system performance and response. speed. Common caching technologies include page caching, database caching, object caching, etc.

2. How to use caching technology to solve high concurrency processing problems?

In PHP, we can use Memcached or Redis as a cache server to store some commonly used data in the cache server, thereby reducing the pressure on the database. The following is a sample code:

addServer("127.0.0.1", 11211);

// 检查缓存中是否存在数据
$key = "user_123";
$user = $memcached->get($key);

// 如果缓存中不存在数据，则从数据库中获取，并存储到缓存中
if (!$user) {
    $user = getUserFromDatabase();

    // 将数据存储到缓存中，过期时间设置为1小时
    $memcached->set($key, $user, 3600);
}

// 使用$user数据进行业务逻辑处理
// ...

// 清除缓存
$memcached->delete($key);

3. How to handle the update and deletion of cached data?

When the data is updated, the data in the cache needs to be updated in time. You can update the data in the corresponding cache while updating the database data. In addition, when data is deleted, the data in the cache must also be deleted simultaneously.

The following is sample code for updating and deleting cache:

set($key, $user, 3600);

// 删除数据库中的数据
deleteUserFromDatabase($userId);

// 删除缓存中的数据
$memcached->delete($key);

4. How to avoid cache penetration and cache penetration issues?

Cache penetration means that when a user requests data that does not exist in the cache or database, it will cause the database to be accessed every time, causing excessive pressure on the database. When reading data, you can first check whether the data exists in the cache. If it does not exist, return a default value and cache the default value in the cache to avoid multiple accesses to the database.

Cache breakdown means that after a hotspot data fails, a large number of concurrent requests happen to access the data, causing multiple requests to access the database at the same time. In order to avoid cache breakdown, a short-lived mutex can be set up. When the cache is invalid, only one request is allowed to access the database for data update, and other requests wait and read the updated cache data.

Sample code:

get($key);

// 如果缓存中不存在数据，则加锁
if (!$user) {
    if ($memcached->add($key . "_lock", 1, 60)) {
        // 从数据库中获取数据
        $user = getUserFromDatabase();

        // 将数据存储到缓存中，过期时间设置为1小时
        $memcached->set($key, $user, 3600);

        // 解锁
        $memcached->delete($key . "_lock");
    } else {
        // 等待并读取更新后的缓存数据
        while (!$user) {
            usleep(1000);
            $user = $memcached->get($key);
        }
    }
}

// 使用$user数据进行业务逻辑处理
// ...

Summary:

By using caching technology, we can effectively solve the problem of high concurrency processing in PHP. Using a cache server to store commonly used data can greatly reduce the burden on the database and improve system performance and response speed. At the same time, we also need to pay attention to updating and deleting cache data, and reasonably deal with cache penetration and cache breakdown issues.

By rationally using caching technology, we can improve the concurrent processing capabilities of the PHP website and provide a better user experience.

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