How to implement Redis database cluster in PHP

Redis is a commonly used in-memory database with the characteristics of high-speed reading and writing, rich data structures, and persistence. It has become one of the very important tools in web applications. With the expansion of business and the increase in data volume, a single Redis server can no longer meet business needs. At this time, it is necessary to use a Redis database cluster to ensure the high availability and scalability of data.

This article will introduce how to use PHP to implement a Redis database cluster. The steps are as follows:

1. Redis cluster architecture

The Redis cluster adopts a distributed architecture, which is implemented through sharding Data processing and storage. A Redis cluster consists of multiple Redis servers. Each server has multiple Redis instances, and each instance stores a portion of data. The client routes data requests to designated nodes through the node routing algorithm, and master-slave replication is used between each node to achieve data synchronization and backup.

2. Install Redis extension

Using Redis in PHP requires installing the Redis extension. The Redis extension provides the Redis PHP interface, which can easily interact with the Redis server. You can use the PECL command to install the Redis extension. The specific operations are as follows:

1. Download the Redis extension source code:

wget https://github.com/phpredis/phpredis/archive/5.3.0.tar.gz

2. Unzip the source code package:

tar zxvf 5.3.0.tar.gz

3. Switch to the decompressed directory:

cd phpredis-5.3.0

4. Compile and install the Redis extension:

phpize
./configure
make && make install

5. Modify the php.ini file , add the following content at the end of the file:

extension=redis.so

6. Restart php-fpm or apache service:

sudo service php-fpm restart

3. Use Redis cluster

When using Redis cluster, you need to pay attention to the following points:

1. Each node in the Redis cluster has its own ID, and the IP and port of the node can be obtained through the ID.
2. Each node in the Redis cluster has a virtual slot number range. The client maps the Key to the slot number through the hash function, and then finds the corresponding node based on the slot number.
3. Redis cluster uses the CRC16 algorithm by default to calculate the slot number, and you can use the consistent hashing algorithm to customize the algorithm.

The following code shows how to use Redis cluster:

<?php
$nodes = [
    ['id' => 'node-1', 'host' => '10.10.0.1', 'port' => 6379],
    ['id' => 'node-2', 'host' => '10.10.0.2', 'port' => 6379],
    ['id' => 'node-3', 'host' => '10.10.0.3', 'port' => 6379],
];
$options = [
    'cluster' => 'redis',
    'timeout' => 1.5,
];
$cluster = new RedisCluster(null, $nodes, $options);
$cluster->set('key', 'value');
echo $cluster->get('key');

The above code defines three Redis nodes, corresponding to three servers respectively. Each node is defined by IP and port. Create a Redis cluster object through the constructor of the RedisCluster class, and use the set and get methods to operate on the Redis database.

4. Redis Cluster Management

In the Redis cluster, there are several commonly used commands for cluster management:

1. CLUSTER NODES: Query all node information in the cluster .
2. CLUSTER KEYSLOT : Calculate which slot number the given Key belongs to.
3. CLUSTER COUNTKEYSINSLOT : Query the number of Keys contained in the specified slot number.
4. CLUSTER ADDSLOTS [ ...]: Assign the specified slot number to the current node.
5. CLUSTER SETSLOT MIGRATING : Migrate the specified slot number to other nodes.
6. CLUSTER SETSLOT IMPORTING : Import the specified slot number from other nodes to the current node.
7. CLUSTER REPLICATE : Sets the node as a slave node of the specified node.
8. CLUSTER FAILOVER [FORCE|TAKEOVER]: Set the specified node as the master node.

The above commands require the use of the Redis command line client. The Redis command line client can be installed using the following command:

sudo apt install redis-tools

5. Summary

This article Introduces the methods and steps for implementing a Redis database cluster using PHP. Redis cluster adopts a distributed architecture, which can realize data processing and storage through sharding, and realize data synchronization and backup through master-slave replication, thus ensuring the high availability and scalability of data. To use Redis cluster in PHP, you need to install the Redis extension and then use the RedisCluster class to perform data operations. Cluster management can be operated through the Redis command line client, and operations such as adding, deleting, and migrating cluster nodes can be performed.

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