How to implement Memcached database cluster in PHP

With the rapid development of Internet applications, data storage and processing are becoming increasingly large and complex. In this context, Memcached, as a high-performance, lightweight distributed memory cache system, has gradually become an indispensable part of the Internet application field. In the PHP language, Memcached can interact with the Memcached server by extending the built-in Memcached class. In the actual production environment, we need to build a Memcached database cluster to ensure the high availability and performance of the system.

This article will introduce how to implement a Memcached database cluster in PHP, including the following aspects:

1. Install and configure the Memcached server
2. Use PHP extensions to access the Memcached server
3. Building a Memcached database cluster
4. Cluster expansion and failover processing

1. Install and configure the Memcached server

In a Linux environment, install And configuring the Memcached server is very simple. Memcached can be installed through the following command:

sudo apt-get install memcached

After the installation is completed, Memcached will listen on port 11211 by default. You can use the following command to check the server status:

memcached-tool localhost:11211 stats

If everything is normal, you can start Use the Memcached extension in PHP to operate the server.

2. Use PHP extension to access the Memcached server

In PHP, the Memcached extension provides a set of API functions to interact with the Memcached server. The following are some commonly used API functions:

$mem = new Memcached();
$mem->addServer('localhost', 11211); // 添加服务器
$mem->set('key', 'value', 60); // 设置值（过期时间60秒）
$value = $mem->get('key'); // 获取值
$mem->delete('key'); // 删除值

It is very simple to use PHP extension to access the Memcached server, but if you need to achieve high availability and performance, a single server is definitely not enough. At this time, you need to consider building a Memcached database cluster.

3. Build a Memcached database cluster

There are two common ways to build a Memcached database cluster: master-slave replication and distributed storage. This article will introduce how to build a cluster by using distributed storage.

Distributed storage can be achieved by running Memcached servers on multiple servers and spreading the data across different servers. In distributed storage, data is usually mapped to the corresponding server based on the hash value of the key value. To ensure that data is evenly distributed across different servers, a consistent hashing algorithm can be used.

The implementation of the consistent hash algorithm is as follows:

First, hash the addresses of all Memcached servers to obtain a hash ring (i.e. a longer binary string) . Then, the key values ​​of all key-value pairs are hashed, and then mapped to the hash ring, so that each key value corresponds to a position on the ring. Next, map the addresses of all Memcached servers to locations on the hash ring. When a key value needs to be written to the cluster, its hash value is first calculated and the corresponding position is found on the ring. Then, go clockwise to find the address of the first Memcached server and save the data in that server. When obtaining a certain key value, first calculate its hash value and find the corresponding position on the ring. Then, look for the address of the first Memcached server in a clockwise direction and check whether the data is saved. If not, continue looking backwards for the next server until you find it.

The following is a sample code for using PHP extension to build a Memcached database cluster:

$mem = new Memcached();
$servers = array(
    array('mem1.example.com', 11211),
    array('mem2.example.com', 11211),
    array('mem3.example.com', 11211),
);
$mem->setOption(Memcached::OPT_DISTRIBUTION, Memcached::DISTRIBUTION_CONSISTENT); // 用一致性哈希分布数据
$mem->setOption(Memcached::OPT_LIBKETAMA_COMPATIBLE, true); // 使用libketama的算法
$mem->addServers($servers); // 添加所有服务器

4. Cluster expansion and failover processing

In the actual production environment, cluster expansion and Failover handling is very important.

For cluster expansion, you can improve the performance of the Memcached cluster by adding new servers or increasing the memory and number of connections of the server. When a new server is added, all data needs to be redistributed across different servers. If you don't want to explicitly reallocate the data, you can wait until the expiration time expires.

For failover processing, when some servers in the cluster fail, a timely response is required. Failover can be handled by the following methods:

1. Detect server status: Use methods such as the ping command or Memcached's STAT command to detect the status of the server.
2. Mark the failed server: Through the Memcached::failureCallback function, you can mark the server when it fails and perform corresponding failover processing.
3. Redistribute data: Redistribute the data in the error server to other normal servers.
4. Restart the error server: If the server only fails temporarily, you can try to restart the server.

To sum up, by using PHP extension, it is very convenient to realize the read and write operations of Memcached database. By using distributed storage, a Memcached cluster with high availability and performance can be built. At the same time, during cluster expansion and failover processing, timely response and processing are required to ensure the stability and reliability of the cluster.

The above is the detailed content of How to implement Memcached database cluster in PHP. For more information, please follow other related articles on the PHP Chinese website!