How to use distributed cache to improve the concurrency performance of PHP programs?

How to use distributed cache to improve the concurrency performance of PHP programs?

Overview:
When developing high-concurrency PHP programs, we often encounter performance bottlenecks caused by frequent database access. To solve this problem, we can use a distributed cache system to improve concurrency performance. This article will introduce how to use the distributed cache system Redis to optimize the concurrency performance of PHP programs and provide corresponding code examples.

1. Installation and Configuration Redis
   First, we need to install Redis and make sure it is running properly on the server. Redis can be installed through the following command:

   sudo apt-get install redis-server

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   After the installation is complete, start the Redis server:

   sudo systemctl start redis

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   You can verify the running status of the Redis server by checking whether it is running:

   redis-cli ping

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   If "PONG" is returned, it means that the Redis server is running normally.

2. Redis Extension
   In order to use Redis in PHP, we need to install the Redis extension. You can install the Redis extension through the following command:

   sudo apt-get install php-redis

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   After the installation is complete, edit the PHP configuration file php.ini and ensure that the following lines are not commented out:

   extension=redis.so

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   Restart the PHP server to enable the configuration Effective:

   sudo systemctl restart php-fpm

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3. Use Redis to cache query results
   In PHP programs, we often need to frequently access the database to obtain data. In order to reduce the burden on the database, we can use Redis to cache query results, thereby improving concurrency performance.

   <?php
   // 初始化 Redis
   $redis = new Redis();
   $redis->connect('localhost', 6379); // 默认的 Redis 服务器地址和端口
   
   function getDataFromDatabase($id) {
    // 模拟从数据库中获取数据的过程
    sleep(2);
    return "data_" . $id;
   }
   
   function getDataFromCache($id) {
    global $redis;
    return $redis->get($id);
   }
   
   function saveDataToCache($id, $data) {
    global $redis;
    $redis->set($id, $data);
    $redis->expire($id, 60); // 设置缓存的过期时间为 60 秒
   }
   
   function getData($id) {
    $data = getDataFromCache($id);
    if (!$data) {
        $data = getDataFromDatabase($id);
        saveDataToCache($id, $data);
    }
    return $data;
   }
   
   $id = $_GET['id'];
   $data = getData($id);
   echo $data;
   ?>

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   In the above sample code, we use Redis cache to store query results. First, the program will check whether the required data already exists in the cache. If it exists, the data in the cache will be used directly. If it does not exist in the cache, the data will be obtained from the database and saved to the Redis cache. At the same time, the cache will be set. Expiration time is 60 seconds.

By caching query results, we can avoid frequent access to the database and improve concurrency performance. In addition, by setting an appropriate cache expiration time, we can flexibly control the validity period of cached data.

4. Distributed Cache
   In order to further improve concurrency performance, we can use a distributed cache system to store cached data distributedly on multiple servers.

When we use multiple Redis servers, we can use a hash function to decide which Redis server to store the data on. The following is a sample code that uses a consistent hash algorithm to implement distributed caching:

<?php
// 初始化 Redis 服务器地址和端口
$redisServers = [
    '127.0.0.1:6379', '127.0.0.1:6380', '127.0.0.1:6381'
];

// 初始化 Redis 连接
$redisConnections = [];
foreach ($redisServers as $server) {
    $redis = new Redis();
    list($host, $port) = explode(":", $server);
    $redis->connect($host, $port);
    $redisConnections[] = $redis;
}

function getDataFromCache($id) {
    global $redisConnections;
    $hash = crc32($id); // 使用 CRC32 哈希函数计算哈希值
    $index = $hash % count($redisConnections); // 根据哈希值选择 Redis 服务器
    return $redisConnections[$index]->get($id);
}

function saveDataToCache($id, $data) {
    global $redisConnections;
    $hash = crc32($id);
    $index = $hash % count($redisConnections);
    $redisConnections[$index]->set($id, $data);
    $redisConnections[$index]->expire($id, 60);
}

$id = $_GET['id'];
$data = getDataFromCache($id);
if (!$data) {
    $data = getDataFromDatabase($id);
    saveDataToCache($id, $data);
}
echo $data;
?>

In the above sample code, we use a consistent hash algorithm to decide which Redis server to store data on. First, we calculate the hash value of the key through a hash function, and then select a Redis server to store the data based on the hash value. This way, data can be distributed across multiple Redis servers, improving concurrency performance.

The above is the method and sample code for using the distributed cache system Redis to improve the concurrency performance of PHP programs. By caching query results and distributed caching, we can effectively reduce the burden on the database and improve the concurrency performance of PHP programs. Hope this article is helpful to you!

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