How to combine nginx with keepalived to achieve high availability

Introduction to keepalived

The function of keepalived is to detect the status of the server. If a web server is down or there is a work failure, keepalived will detect it and will The faulty server is removed from the system, and other servers are used to replace the server's work. When the server is working normally, keepalived automatically adds the server to the server group. All these tasks are completed automatically without manual intervention. All that needs to be done manually is Repair failed servers.

System architecture diagram

Implementation steps

1. Environment configuration

##1.1 Install nginx

Install related dependencies

yum install pcre-devel zlib zlib-devel openssl openssl-devel

Upload and decompress the compressed package

tar zxvf nginx-1.12.2.tar.gz

Create directory, detect configuration

mkdir -p /usr/local/nginx
./configure --prefix=/usr/local/nginx

Precompile and install

make && make install

Start and stop related commands

cd /usr/local/nginx/sbin/
./nginx
./nginx -s stop
./nginx -s start

1.2 Install keepalived

yum install -y keepalived

2. Host configuration

Modify keepalived configuration file

vim /etc/keepalived/keepalived.conf

The modified content is as follows

#新增的配置
vrrp_script chk_http_port {
 script "/shell/nginx_check.sh" #脚本地址
 interval 2 #检测脚本执行的间隔
 weight 2 #比重
}

vrrp_instance vi_1 {
 state master #主服务器为master,从服务器为backup
 interface eth0 #网卡
 virtual_router_id 51 #主、备机的virtual_router_id必须相同
 priority 100 #主、备机不同的优先级，主机优先级较大，备机值较小，默认是100
 advert_int 1
 authentication {
  auth_type pass
  auth_pass 1111
 }
 #虚拟ip地址
 virtual_ipaddress {
  192.168.126.88
 }
}

Create a script file

mkdir /shell/nginx_check.sh
vim /shell/nginx_check.sh

The content of the script file is as follows

#!/bin/bash
a=`ps -c nginx –no-header |wc -l`
if [ $a -eq 0 ];then
  /usr/local/nginx/sbin/nginx
  sleep 2
  if [ `ps -c nginx --no-header |wc -l` -eq 0 ];then
    killall keepalived
  fi
fi

3. Slave configuration

Modify keepalived configuration file

vrrp_instance vi_1 {
  state backup #主服务器为master,从服务器为backup
  interface eth0 #网卡
  virtual_router_id 51 #主、备机的virtual_router_id必须相同
  priority 50 #主、备机不同的优先级，主机优先级较大，备机值较小
  advert_int 1
  authentication {
    auth_type pass
    auth_pass 1111
  }
  #虚拟ip地址
  virtual_ipaddress {
    192.168.126.88
  }
}

4.Start the service

Start

service keepalived start

View virtual ip address

ip addr
1: lo: <loopback,up,lower_up> mtu 65536 qdisc noqueue state unknown 
  link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
  inet 127.0.0.1/8 scope host lo
  inet6 ::1/128 scope host 
    valid_lft forever preferred_lft forever
2: eth0: <broadcast,multicast,up,lower_up> mtu 1500 qdisc pfifo_fast state up qlen 1000
  link/ether 00:0c:29:4f:31:ce brd ff:ff:ff:ff:ff:ff
  inet 192.168.126.100/24 brd 192.168.126.255 scope global eth0
  inet 192.168.126.88/32 scope global eth0
  inet6 fe80::20c:29ff:fe4f:31ce/64 scope link 
    valid_lft forever preferred_lft forever

5. Turn off the firewall test

Close the firewall

service iptables stop
#查看防火墙是否开机自启动
chkconfig --list | grep iptables
chkconfig iptables off

Log in to the virtual ip address to view

http://192.168.126.88/

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