How to implement remote disaster recovery of Memcached database with PHP

As the scale of Internet applications continues to expand, data disaster recovery has become an inevitable topic. Memcached is an efficient cache database, but its local storage method makes it a risk of single point of failure. Therefore, in order to improve the reliability of Memcached, disaster recovery needs to be performed off-site. This article will introduce how to use PHP to implement remote disaster recovery of Memcached database.

Memcached is a memory cache database. Its main function is to cache frequently used data to improve response speed. Memcached is generally used in distributed data caching, and its deployment method is also very simple. However, Memcached's local storage method has a single point of failure problem. If the Memcached node fails, all data will be lost. Therefore, in a production environment, we must use Memcached for disaster recovery to improve the reliability of the entire system.

To implement remote disaster recovery of the Memcached database, we first need to understand the master-slave replication mechanism of Memcached. The Memcached master-slave replication mechanism refers to setting one Memcached node as the master node and other nodes as slave nodes. The master node stores all data and synchronizes the data to the slave nodes. If the master node fails, the slave node can automatically switch to the master node to ensure data reliability.

In practical applications, we can implement master-slave replication and switching of Memcached nodes through PHP code. In PHP, we can use the Memcached class to operate the Memcached database. The addServer method is provided in the Memcached class to add a Memcached node and specify the type of node (master node or slave node). The following is a simple PHP code example:

addServer('127.0.0.1', 11211);

/* 添加从节点 */
$m->addServer('127.0.0.2', 11211, 1);

?>

In this example, we have added two Memcached nodes, where the 127.0.0.1 node is set as the master node and the 127.0.0.2 node is set as the slave node. We can specify the type of node through the third parameter, 0 represents the master node, and 1 represents the slave node.

The switching of Memcached nodes needs to meet two conditions: first, the master node fails, and second, the slave node automatically switches to the master node. In PHP, we can determine whether the master node is running normally by using the getStats method of the Memcached class. If the master node fails, the slave node will automatically switch to the master node. The following is a PHP code example:

addServer('127.0.0.1', 11211);

/* 添加从节点 */
$m->addServer('127.0.0.2', 11211, 1);

/* 判断主节点是否正常运行 */
$stats = $m->getStats();
if ($stats['127.0.0.1:11211']['pid'] == 0) {
    /* 从节点自动切换成主节点 */
    $m->setOption(Memcached::OPT_SERVER_FAILURE_LIMIT, 1);
    $m->setOption(Memcached::OPT_RETRY_TIMEOUT, 5);
    $m->setOption(Memcached::OPT_AUTO_EJECT_HOSTS, true);
}

?>

In this example, we use the getStats method to get the status information of all nodes. If the pid of the master node is 0, it means that the master node has failed. We can use the setOption method to set the parameters for automatically switching from the slave node to the master node, including failure limit, retry time and automatic node ejection. In this way, in the event of a master node failure, the slave node will automatically switch to the master node to ensure data reliability and normal operation of services.

In short, PHP is a very flexible and efficient programming language suitable for developing high-reliability Memcached databases. By using the addServer method and getStats method of the Memcached class, we can easily implement master-slave replication and switching of Memcached nodes, thereby realizing off-site disaster recovery of the Memcached database and ensuring the reliability and stability of the application.

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