How to achieve Nginx high availability-Nginx-php.cn

Preparation:

192.168.16.128

192.168.16.129

Two virtual machines. Install Nginx

Install Nginx

Update yum source file:

rpm -ivh http://nginx.org/packages/centos/7/noarch/RPMS/nginx-release-centos-7-0.el7.ngx.noarch.rpm

wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo

Install Nginx:

yum -y install nginx

Operation command:

systemctl start nginx; #Start Nginx

systemctl stop nginx; #Stop Nginx

What is high availability?

High availability HA (High Availability) is one of the factors that must be considered in the design of distributed system architecture. It usually refers to reducing the time when the system cannot provide services through design. If a system can always provide services, then the availability is 100%, but there are unforeseen circumstances. So we can only try to reduce service failures as much as possible.

solved problem?

In production environments, Nginx is often used as a reverse proxy to provide external services. However, Nginx will inevitably encounter failures one day, such as server downtime. When Nginx goes down, all externally provided interfaces will become inaccessible.

Although we cannot guarantee that the server is 100% available, we must find ways to avoid this tragedy. Today we use keepalived to implement Nginx

High availability.

Dual-machine hot backup solution

This solution is the most common high-availability solution among domestic enterprises. Dual-server hot backup actually means that one server is providing services and the other is in standby state for a certain service. When one server is unavailable, the other one Will take his place.

What is keepalived?

Keepalived software was originally designed for LVS load balancing software to manage and monitor the status of each service node in the LVS cluster system. Later, it added VRRP (Virtual Router Redundancy Protocol) to achieve high availability. Function. Therefore, in addition to managing LVS software, Keepalived can also be used as a high-availability solution software for other services (such as Nginx, Haproxy, MySQL, etc.)

Failover mechanism

Failover transfer between Keepalived high-availability services is implemented through VRRP.

When the Keepalived service is working normally, the primary Master node will continuously send (multicast) heartbeat messages to the backup node to tell the backup Backup node that it is still alive. When the primary Master node fails, it cannot send heartbeat messages and the backup node will not be able to send heartbeat messages. Therefore, the node can no longer detect the heartbeat from the main Master node, so it calls its own takeover program to take over the IP resources and services of the main Master node. When the master node recovers, the backup node will release the IP resources and services it took over when the master node failed, and return to its original backup role.

Implementation process

Install keepalived

You can install it directly using the yum method, which will automatically install dependencies:

yum -y install keepalived

Modify the host (192.168.16.128) keepalived configuration file

Installation using yum will produce the configuration file under /etc/keepalived:

vi keepalived.conf

keepalived.conf:

#Detection script

vrrp_script chk_http_port {

Script "/usr/local/src/check_nginx_pid.sh" #Heartbeat execution script to detect whether nginx is started

interval 2 interval 2 weight 2 #weight

}

#vrrp instance definition section

vrrp_instance VI_1 {

state MASTER # Specify the role of keepalived, MASTER is the main one and BACKUP is the backup one

interface ens33 # The current network interface card for vrrp communication (current centos network card) Use ifconfig to check your specific network card

Virtual_router_id 66 # Virtual route number, master and slave must always be

Priority 100 # Priority, the larger the value, the higher the priority for processing the request

advert_int 1 # Check interval, the default is 1s (vrrp multicast cycle seconds)

#Authorized access

authentication {

auth_type PASS #Set the verification type and password. MASTER and BACKUP must use the same password for normal communication

auth_pass 1111

}

track_script {

chk_http_port #(call detection script)

}

virtual_ipaddress {

192.168.16.130 192.168.16.130 # Define virtual ip (VIP), you can set more than one, one per line

}

VIP can be configured in virtual_ipaddress, and services can be accessed online through VIP.

The interface needs to be set according to the server network card. The usual viewing method is ip addr

Authentication configuration authorization access to the backup machine also requires the same configuration

Modify the backup machine (192.168.16.129) keepalived configuration file

keepalived.conf:

#Detection script

vrrp_script chk_http_port {

Script "/usr/local/src/check_nginx_pid.sh" #Heartbeat execution script to detect whether nginx is started

interval 2 weight 2 #weight

}

#vrrp instance definition section

vrrp_instance VI_1 {

State Backup#Specify the role of Keepalived, Master mainly, backup as a reserve

interface ens33 # The current network interface card for vrrp communication (current centos network card) Use ifconfig to check your specific network card

virtual_router_id 66 # Virtual route number, master and slave must always be

priority 99 Advert_int 1#Check the interval, the default is 1s (VRRP broadcast cycle seconds)

#Authorized access

authentication {

auth_type PASS #Set the verification type and password. MASTER and BACKUP must use the same password for normal communication

auth_pass 1111

}

track_script {

chk_http_port #(call detection script)

}

virtual_ipaddress {

192.168.16.130 192.168.16.130 # Define virtual ip (VIP), you can set more than one, one per line

}

Detection script:

#!/bin/bash

#Detect whether nginx is started

A=`ps -C nginx --no-header |wc -l`

if [ $A -eq 0 ];then #If nginx is not started, start nginx systemctl start nginx #Restart nginx

If [ `ps -C nginx --no-header |wc -l` -eq 0 ];then # If nginx fails to restart, stop the keepalived service and perform VIP transfer

Killall keepalived

Script authorization: chmod 775 check_nginx_pid.sh

Note: The script must be authorized, otherwise it will not have permission to access. Here we have two servers to execute, VIP (virtual_ipaddress:192.168.16.130). In the production environment, we access the service directly through VIP.

Simulate nginx failure:

Modify the Nginx html page that the two servers access by default as a difference.

First visit 192.168.16.130 and access it through VIP. The page displays 192.168.16.128; indicating that the service is currently provided by the main server.

At this time, the 192.168.16.128 main server executes the command:

systemctl stop nginx; #stop nginx

Visit vip (192.168.16.130) again and find that the page still displays: 192.168.16.128. This is an automatic restart in the script.

Now directly close the 192.168.16.128 server, visit VIP here (192.168.16.130) and now find that the page displays 192.168.16.129. At this time, keepalived will automatically failover, and a high-availability solution for an enterprise-level production environment has been established.

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