PHP method to implement database load balancing failure recovery

As the scale of enterprise applications continues to increase, database systems have become an indispensable part of enterprise IT architecture. However, the performance of a database system is often limited by the processing capabilities of a single server. As business volume increases, a single server may not be able to meet business requirements. Therefore, database load balancing has become one of the important means for enterprises to deal with high concurrent requests. . This article will introduce how PHP implements database load balancing failure recovery.

1. Principle of database load balancing

Database load balancing refers to a method that distributes database access requests among multiple database servers so that multiple servers can share the request pressure. technology. Its main principles include the following aspects:

1. The client initiates a request: The client sends a request to the database server.

2. The load balancer receives the request: The request passes through the load balancer and is distributed among multiple database servers.

3. The database server processes the request: the database server that receives the request processes it and returns the result.

4. The load balancer receives the return results: The return results are processed by the load balancer and returned to the client.

2. How PHP implements database load balancing

PHP language is an open source scripting language. It is widely used in the development of Web applications due to its simplicity, ease of use, and excellent performance. . Database load balancing can be implemented by developing some load balancer programs based on PHP, such as Nginx-Lua, Haproxy and other load balancers developed using PHP.

Taking Haproxy as an example, the following describes its implementation process in PHP.

1. Installing Haproxy

First you need to install Haproxy in the Linux system. Enter the following command in the terminal:

sudo apt-get install haproxy

2. Configure Haproxy

After the installation is complete, you need to configure Haproxy Configuration, the configuration here can be completed by editing the /etc/haproxy/haproxy.cfg file.

By default, the configuration in the haproxy.cfg file is not enabled and needs to be modified. Modify according to the following template. Two backend servers are used here:

global
log /dev/log local0
log /dev/log local1 notice
chroot /var/lib/ haproxy
user haproxy
group haproxy
daemon

defaults
log global
mode http
option httplog
option dontlognull
retries 3
timeout client 5000
timeout connect 5000
timeout server 5000
errorfile 400 /etc/haproxy/errors/400.http
errorfile 403 /etc/haproxy/errors/403.http
errorfile 408 /etc/haproxy/errors/408.http
errorfile 500 /etc/haproxy/errors/500.http
errorfile 502 /etc/haproxy/errors/502.http
errorfile 503 /etc/haproxy/ errors/503.http
errorfile 504 /etc/haproxy/errors/504.http

frontend main
bind *:80
acl url_static path_beg -i /static /images /javascript / stylesheets
acl url_static path_end -i .jpg .gif .png .css .js
use_backend static if url_static
default_backend php_backend

backend php_backend
balance roundrobin
option httpclose
option forwardfor
server server1 192.168.1.101:80 check
server server2 192.168.1.102:80 check

3. PHP connects to Haproxy

PHP and Haproxy The connection between them is through tcp/ip. PHP uses the socket_create function and socket_connect function to create and connect sockets respectively to implement communication with Haproxy.

The specific code is as follows:

$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
$srv_ip = "192.168.1.100";
$srv_port = 80;
socket_connect($socket, $srv_ip, $srv_port);

$data = "GET / HTTP/1.1
";
$data .= "Host: 192.168.1.100
";
$data .= "Connection: Close

";

socket_write($socket, $data, strlen($data));

$response = "";
while ($out = socket_read($socket, 2048)) {
$response .= $out;
}

echo $response;

4. Failure recovery

In the database load balancer, if the backend server fails, there needs to be a mechanism for failure recovery. The failure recovery mechanism in Haproxy is to check the status of the back-end server. Once the status of a server changes to recovery, Haproxy will forward the request to the server again.

The specific method is to add the following statement in haproxy.cfg:

option httpchk HEAD / HTTP/1.1
Host:localhost

Among them, option httpchk is used For the configuration of checking the status of the backend server, HEAD / HTTP/1.1
Host:localhost is used to check the request header information of the backend server. This can be modified according to your own needs.

3. Summary

This article mainly introduces the method of PHP to achieve database load balancing failure recovery, including the installation and configuration of Haproxy and writing PHP programs to communicate with Haproxy. Generally speaking, PHP has the advantages of easy development and flexible configuration. Implementing database load balancing with PHP as the center can provide richer functions and better performance. However, it should be noted that for load balancing in complex situations, it is recommended to use a professional load balancer.

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