PHP method to implement database cluster expansion

Database cluster is a commonly used high-availability solution in modern large-scale websites and enterprise-level applications to achieve load balancing and data redundancy. As business scale continues to expand, capacity expansion or reduction has become an important task in cluster management. This article will introduce how to use PHP language to expand the database cluster.

1. Database Cluster

A database cluster is a distributed system of multiple database servers that work together to process large data sets. Each server stores a portion of the data, allowing the entire data set to be spread across all nodes. Clustering can also ensure that if a node fails, the system can continue to work normally.

There are two types of database clusters: master-slave replication cluster and shared storage cluster. A master-slave replication cluster refers to a cluster composed of one master node and multiple slave nodes. The master node receives all data and write requests, and then copies the data to the slave node, which only receives read requests. A shared storage cluster means that multiple nodes have the same data, and the nodes share storage to complete data reading and writing operations. No matter what kind of cluster it is, capacity expansion is an important means to horizontally expand the system.

2. PHP

PHP is a popular open source server-side scripting language, especially suitable for use in web development. PHP provides many libraries and functions to access databases, including MySQL, PostgreSQL, and Oracle.

In PHP, we can use the PDO (PHP Data Objects) extension to handle database connections and operations. PDO provides a unified interface to access a variety of databases, including MySQL, PostgreSQL and SQLite. PDO allows us to use SQL statements to perform operations such as query, insert, update, and delete.

3. Database cluster expansion

Capacity expansion is a necessary means to expand the system scale. It improves the throughput and fault tolerance of the cluster. In a database cluster, expansion can be divided into two situations: vertical expansion and horizontal expansion.

Vertical expansion is to increase the resources of a single node, such as memory or CPU, to improve the performance of the node. The disadvantage of vertical expansion is that it is expensive and cannot meet the needs of horizontal expansion, that is, it cannot handle a large number of concurrent requests. Therefore, in practical applications, horizontal expansion is usually used.

Horizontal expansion is to increase the processing capacity of the cluster by adding nodes. Adding nodes increases the throughput of the cluster and reduces the load on the nodes. In practical applications, we can expand the capacity by adding nodes, that is, expand the database cluster from one node to multiple nodes, and balance the load to achieve high availability and high performance.

4. Implementation method

In PHP, we can use PDO extension to access the database and expand the database cluster. The following describes how to use PDO extension to execute SQL statements and select one of multiple nodes to execute SQL queries.

First, we need to install the PDO extension. In the Ubuntu system, it can be installed through the following command:

sudo apt-get install php7.4-pdo php7.4-mysql

Next, we can use the following code to connect to the database:

$dsn = "mysql:host=node1;port=3306;dbname=mydatabase";
$username = "username";
$password = "password";
$pdo = new PDO($dsn, $username, $password);

Among them, $dsn is the data source name, specifying the connection Hostname and port number. In this example, we use node 1 as the master node. $username and $password are the username and password for connecting to the database.

Next, we can execute the SQL query:

$query = "SELECT * FROM mytable";
$stmt = $pdo->query($query);
$results = $stmt->fetchAll();

In the above code, $query is the query statement, and $stmt is a PDOStatement object, which contains the query result information. $results is an array containing all query results.

If we want to distribute query requests among multiple nodes, we can use the following code to achieve it:

$nodes = array("node1", "node2", "node3");
$dsn_template = "mysql:host=%s;port=3306;dbname=mydatabase";
foreach ($nodes as $node) {
    $dsn = sprintf($dsn_template, $node);
    try {
        $pdo = new PDO($dsn, $username, $password);
        $stmt = $pdo->query($query);
        $results = $stmt->fetchAll();
        break;
    } catch (PDOException $e) {
        // handle exception
        continue;
    }
}

In the above code, $nodes is an array of node names. We use a loop to visit the nodes one by one and execute the query. If the connection fails, continue accessing the next node until the connection is successful.

In this way, we can expand the database cluster. Adding nodes increases the throughput of the cluster and reduces the load on the nodes. Horizontal expansion can improve the efficiency and reliability of the cluster and ensure high availability and performance of the system.

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