Using Redis to implement sharded storage in PHP

With the continuous development of Internet applications, the demand for data storage and processing continues to increase. However, traditional relational databases have certain bottlenecks in performance and scalability. In order to solve this problem, NoSQL database came into being. Among them, Redis, as a high-speed NoSQL database, is widely used in fields such as caching, message queues, and key-value storage. This article will introduce in detail how to use PHP to connect to Redis and implement sharded storage to improve read and write performance and scalability.

1. Basic knowledge of Redis

1. Data structure of Redis

Redis supports a variety of data structures, including strings, hash tables, and lists , sets and ordered sets, etc. In applications, Redis is usually used as a cache to reduce server pressure by caching commonly used data.

2. Redis persistence method

Redis supports two persistence methods: RDB and AOF. RDB is implemented by regularly saving data in memory to snapshots on disk, while AOF records all operations written to Redis so that they can be re-executed when Redis is restarted.

3. Master-slave replication of Redis

Redis supports master-slave replication, which can effectively improve read performance and availability. Master-slave replication allows the master server to synchronize data to multiple slave servers, thereby reducing the pressure on the master server and improving system availability. When the master server fails, it automatically switches to the slave server so that the system can recover quickly.

2. PHP connects to Redis

You can connect to Redis through the PECL extension or the built-in redis extension. Next, the usage of both will be introduced in detail.

1. PECL extension

PECL extension provides more advanced features, such as Redis cluster and sentinel mode, but requires manual compilation and installation.

1) Install PECL extension

First you need to download the Redis extension, then enter the extension directory and execute the following command:

phpize
./configure
make
make install

2) Connect to Redis

Connect Redis needs to set the IP address and port of the Redis server. After the connection is established, related operations can be performed.

$redis = new Redis();
$redis->connect('127.0.0.1', 6379);
$redis->set('name', 'redis');
$name = $redis->get('name');
echo $name;

2. redis extension

The redis extension is the official extension for PHP 5.5 and above. It is very simple to install and use and does not require manual compilation and installation.

1) Install the redis extension

You can install it through yum:

yum install php-redis

You can also download the installation package manually, then unzip and install:

wget https://github.com/phpredis/phpredis/archive/5.2.3.tar.gz
tar -zxvf 5.2.3.tar.gz
cd phpredis-5.2.3
phpize
./configure
make && make install

2) Connect Redis

Connecting to Redis also requires setting the IP address and port of the Redis server. After the connection is established, related operations can be performed.

$redis = new Redis();
$redis->connect('127.0.0.1', 6379);
$redis->set('name', 'redis');
$name = $redis->get('name');
echo $name;

3. Redis sharded storage

When the amount of Redis data is very large, the performance of a single node may reach a bottleneck. To improve performance and availability, sharded storage can be implemented by spreading data across multiple nodes.

Sharded storage allocates data to different nodes in different forms, and each node stores a portion of the data. In this way, the client can find the corresponding data on each node by calculating the hash value of the key.

1. Consistent hashing

Consistent hashing (Consistent hashing) is an algorithm used to solve the distributed performance bottleneck of cache or database. By mapping the hash value of the key onto the ring, the nearest node is found clockwise on the ring as the data storage node. When a node is added or deleted, adjacent nodes will be affected, but other nodes will not be affected.

2. Redis’ sharded storage

Redis’ sharded storage can be implemented through consistent hashing algorithms. The specific steps are as follows:

1) Calculate the hash value of the key and find the corresponding node.

$server = $nodes[crc32($key) % count($nodes)];

2) Connect to the corresponding node and perform related operations.

$redis = new Redis();
$redis->connect($server['host'], $server['port']);
$redis->set($key, $value);

3) When a node is added or deleted, the hash value of the mapping key can be recalculated through the consistent hashing algorithm to evenly distribute the data to the new nodes and delete the original node data on.

4. Implementation process

The following will introduce in detail how to use PHP to connect to Redis to implement sharded storage.

1. Environment preparation

The environment used in this experiment is as follows:

• CentOS 7.6.1810 operating system
• PHP 7.2.22
• Redis 3.2.12

2. Download and install the Redis extension

wget https://github.com/phpredis/phpredis/archive/5.2.3.tar.gz
tar -zxvf 5.2.3.tar.gz
cd phpredis-5.2.3
phpize
./configure
make && make install

3. Write the sharded storage code

The code to connect to Redis and implement sharded storage is as follows:

<?php

// Redis节点列表
$nodes = array(
    array('host' => '127.0.0.1', 'port' => 6379),
    array('host' => '127.0.0.1', 'port' => 6380),
);

// 计算键的散列值，并找到对应的节点
function getServer($key, $nodes)
{
    $server = $nodes[crc32($key) % count($nodes)];
    return $server;
}

// 连接对应的节点，进行相关操作
function redis($key, $value, $nodes)
{
    $server = getServer($key, $nodes);
    $redis = new Redis();
    $redis->connect($server['host'], $server['port']);
    $redis->set($key, $value);
    return true;
}

// 测试代码
$key = 'name';
$value = 'redis';
redis($key, $value, $nodes);
$name = redis->get($key);
echo $name;

?>

5. Summary

This article details how to use PHP to connect to Redis and use consistent hashing The algorithm implements sharded storage to improve read and write performance and scalability. As a high-speed NoSQL database, Redis is widely used and has excellent performance and availability. In actual applications, it is necessary to select an appropriate sharded storage solution based on specific circumstances and pay attention to compatibility and maintainability issues.

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