PHP method to implement database master-slave replication failure recovery

With the rapid development of the Internet, large amounts of data need to be stored and processed, so databases have become an indispensable part of modern application development. In real applications, due to the influence of various factors such as network environment and hardware failures, database master-slave replication failure recovery is often an essential task. In this article, we will introduce how to use PHP to implement database master-slave replication failure recovery method.

1. Introduction to master-slave replication
   Database master-slave replication refers to the process of copying one database (master database) to another or multiple replicas (slave databases) through the network. The master library handles all write operations, while the slave library can only be used for read operations. The advantages of master-slave replication are better scalability, reliability and fast recovery, and it can also provide better performance.
2. Failure Recovery Principle
   Due to unpredictable factors, such as network failure, hardware failure, etc., the slave database may stop working and no longer synchronize with the master database. In order to ensure data integrity and consistency, we need to restore the slave database. The so-called recovery means that even if the slave database is restarted, the data will be synchronized with the master database again.

There are two basic methods to implement database master-slave replication failure recovery: point-in-time recovery and incremental recovery. Instead, we use a point-in-time recovery method, which is the most commonly used method because it requires less backup instances.

3. Implementation steps

First, configure the master-slave replication environment. You can refer to the official website documentation for settings.

(1) Back up the main database data
Back up the main database data through the mysqldump command. It should be noted that you need to use FLUSH TABLES WITH READ LOCK before the backup (to prevent the main database from being modified when backing up the data. data is inconsistent). You need to use the UNLOCK TABLES command to cancel the lock after the backup.

(2) Transfer the backup file to the slave library
Transfer the backup file to the slave library server and store it locally on the server.

(3) Close the slave database
Before performing fault recovery, we need to close the slave database and delete the data.

(4) Restore the master database backup
Use the mysqldump command on the slave database to restore the data backed up from the master database to the slave database.

(5) Configure master-slave database synchronization
Reconfigure master-slave database synchronization and ensure that master-slave database data synchronization is completed.

(6) Restart the slave library
Restart the slave library and confirm whether the data is normal.

4. PHP Fault Recovery
   In practical applications, it is more convenient to use PHP to realize master-slave replication fault recovery. We can write specific scripts according to actual needs. The following is a simple PHP code implementation:

<?php
    $mysql_host = 'localhost';
    $mysql_dbname = 'test';    // 指定数据库名称
    $mysql_user = 'root';
    $mysql_pass = '';
    $mysql_charset = 'utf8';

    // 连接数据库
    try {
        $db = new PDO("mysql:host={$mysql_host};dbname={$mysql_dbname};charset={$mysql_charset}", $mysql_user, $mysql_pass);
    } catch(PDOException $e) {
        echo $e->getMessage();
        exit;
    }

    // 备份主库数据
    exec("/usr/bin/mysqldump -h{$mysql_host} -u{$mysql_user} -p{$mysql_pass} --lock-tables --databases {$mysql_dbname} > /path/to/backup.sql");

    // 传输备份文件到从库
    exec("scp /path/to/backup.sql user@remotehost:/path/to/backup.sql");

    // 关闭从库并删除数据
    $db->query('STOP SLAVE');
    $db->query('RESET SLAVE');

    // 还原主库备份
    exec("/usr/bin/mysql -h{$mysql_host} -u{$mysql_user} -p{$mysql_pass}  {$mysql_dbname} < /path/to/backup.sql");

    // 配置主从库同步
    $db->query('CHANGE MASTER');
    $db->query('START SLAVE');

    // 重新启动从库
    exec('service mysql restart');
?>

5. Summary
   In this article, we introduced how to use PHP to implement database master-slave replication failure recovery. Master-slave replication can improve the scalability and reliability of the database, while failure recovery can ensure the consistency and integrity of the database data. These tasks can be more easily accomplished using scripts written in PHP. Through this article, readers can understand the basic principles of master-slave replication and fault recovery methods, so as to better deal with database replication faults in actual work.

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