Example of how to implement master-slave hot standby using Docker+keepalived+nginx

docker pull centos:7

docker run -it -d --name centos1 -d centos:7

docker exec -it centos1 bash

yum updateyum install -y vimyum install -y wgetyum install -y gcc-c++ yum install -y pcre pcre-devel yum install -y zlib zlib-devel yum install -y openssl openssl--develyum install -y popt-develyum install -y initscripts
yum install -y net-tools

docker commit -a 'cfh' -m 'centos with common tools' centos1 centos_base

docker rm -f centos1
#The systemctl service needs to be used in the container, and /usr/sbin/init needs to be added
docker run -it --name centos_temp -d --privileged centos_base /usr/sbin/init
docker exec -it centos_temp bash

Author: Jianghu Jiujiu Link: https://juejin.im/post/5dc517386fb9a04a9272110b
Source: Nuggets. Copyright belongs to the author. For commercial reproduction, please contact the author for authorization. For non-commercial reproduction, please indicate the source.

#Use yum to install nginx. You need to include the Nginx library. Install the Nginx library rpm -Uvh http://nginx.org/packages/centos/7/noarch/RPMS/nginx-release-centos-7-0.el7.ngx.noarch.rpm
# Install nginx using the following command
yum install -y nginx
#Start nginx
systemctl start nginx.service
#Check whether the startup is successful. The nginx welcome interface appears, indicating that the installation is successful. curl 172.17.0.2

mkdir /etc/keepalivedcp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/Then copy the keepalived script file: cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/ln -s /usr/local/sbin/keepalived /usr/sbin/You can set it to start at boot: chkconfig keepalived on, now we have completed the installation!

#If an error occurs during startup, execute the following command cd /usr/sbin/ 
rm -f keepalived 
cp /usr/local/keepalived/sbin/keepalived /usr/sbin/ 

#Common commands systemctl daemon-reload reloads systemctl enable keepalived.service sets automatic startup at boot systemctl disable keepalived.service cancels automatic startup at boot systemctl start keepalived.service starts systemctl stop keepalived.service stops systemctl status keepalived.service checks service status

#Backup configuration file cp /etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf.backup

rm -f keepalived.conf
vim keepalived.conf
#The configuration file is as follows vrrp_script chk_nginx {
  script "/etc/keepalived/nginx_check.sh"
  interval 2
  weight -20
}

vrrp_instance VI_1 {
  state MASTER
  interface eth0
  virtual_router_id 121
  mcast_src_ip 172.17.0.6
  priority 100
  nopreempt
  advert_int 1
  authentication
    auth_type PASS
    auth_pass 1111
  }

  track_script {
    chk_nginx
  }

  virtual_ipaddress {
    172.17.0.100
  }
}

vim nginx_check.sh
#The following is the script content#!/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

chmod +x nginx_check.sh

systemctl enable keepalived.service

#Open keepalived
systemctl start keepalived.service

curl 172.17.0.100

docker commit -a 'cfh' -m 'centos with keepalived nginx' centos_temp centos_kn

docker rm -f `docker ps -a -q`

docker run --privileged -tid --name centos_master --restart=always centos_kn /usr/sbin/init

docker exec -it centos_master bash

vim /usr/share/nginx/html/index.html 

docker run --privileged -tid --name centos_slave --restart=always centos_kn /usr/sbin/init
docker exec -it centos_slave bash

#Modify the keepalived.conf configuration file, mainly the adjustment of the state and priority parameters. The priority value of the master node must be larger than that of the slave node. vrrp_script chk_nginx {
  script "/etc/keepalived/nginx_check.sh"
  interval 2
  weight -20
}

vrrp_instance VI_1 {
  state SLAVE
  interface eth0
  virtual_router_id 121
  mcast_src_ip 172.17.0.6
  priority 80
  nopreempt
  advert_int 1
  authentication
    auth_type PASS
    auth_pass 1111
  }

  track_script {
    chk_nginx
  }

  virtual_ipaddress {
    172.17.0.100
  }
}

systemctl daemon-reload
systemctl restart keepalived.service

vim /usr/share/nginx/html/index.html 

curl 172.17.0.100

curl 172.17.0.100

curl 172.17.0.100

chkconfig nginx on