Build keepalived to achieve dual-system hot backup, automatic master-slave failover

1. Environment description (the keepalived installation package is at the end of the page, just download it)

Operating system kernel version: CentOS 6.5
Keepalived software version: keepalived-1.2.13.tar.gz  

 2. Environment configuration

Primary Keepalived server IP address 192.168.10.10
Standby Keepalived server IP address 192.168.10.30
Keepalived virtual IP address 192.168.10.20

 

 3. Installation and configuration

First of all, you can build basic services according to my first article {Load Balancing - Reverse Proxy}
Install the support package on both the master and slave servers
[root@localhost ~]# yum -y install kernel-devel openssl-devel popt-devel ipvsadm

Upload keepalived to the /root/ directory on both the master and slave servers

[root@localhost ~]#tar zxf keepalived-1.2.13.tar.gz
[root@localhost ~]# cd keepalived-1.2.13
[root@localhost keepalived-1.2.13]# ./configure --prefix=/ --with-kernel-dir=/usr/src/kernels/2.6.32-431.el6.x86_64
[root@localhost keepalived-1.2.13]# make
[root@localhost keepalived-1.2.13]# make install
[root@localhost keepalived-1.2.13]# chkconfig --add keepalived
[root@localhost keepalived-1.2.13]# chkconfig keepalived on

Fourth, the main server configuration 

[root@localhost ~]#cd /etc/keepalived/
[root@localhost keepalived]#cp keepalived.conf keepalived.conf.backup #Backup a copy to prevent errors
[root@localhost keepalived]#vim keepalived.conf
The configuration content is as follows:
! Configuration File for keepalived

global_defs {
   router_id LVS_DEVEL_R1 #This server name
}

vrrp_instance VI_1 { #Define VRRP hot standby instance
    state MASTER #Hot standby state, MASTER indicates the master server
    interface eth0 #Physical interface carrying the VIP address
    virtual_router_id 1 #Virtual router ID number, consistent for each hot standby group
    priority 100 #Priority, the larger the value, the higher the priority
    advert_int 1 #advertisement interval in seconds
    authentication { #Authentication information, consistent for each hot standby group      
        auth_type PASS #Authentication type
        auth_pass 123456 #Password string
    }
    virtual_ipaddress { #Specify the VIP drift address, you can write multiple
        192.168.10.20    }
}
#Other code takes time to delete all first! ! !
[root@localhost keepalived]#service keepalived restart
[root@localhost keepalived]#ip addr show dev eth0 Check our VIP address and there will definitely be an IP address of 192.168.10.20

  

Five, from the server configuration

[root@localhost ~]#cd /etc/keepalived/
[root@localhost keepalived]#cp keepalived.conf keepalived.conf.backup #Also backup one to prevent errors
[root@localhost keepalived]#vim keepalived.conf
# The configuration content is as follows:
! Configuration File for keepalived

global_defs {
   router_id LVS_DEVEL_R2
}
 
vrrp_instance VI_1 {
    state BACKUP
    interface eth0
    virtual_router_id 1
    priority 10
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 123456
    }
    virtual_ipaddress {
        192.168.10.20  }
}
All other content is also deleted! ! !

[root@localhost keepalived]#service keepalived restart
[root@localhost keepalived]#ip addr show dev eth0
Now when you view from the service, you will only have your own interface IP. Because the main server is still there, the VIP address must still be on the main server. When the main server fails, the backup server will work and immediately take over the VIP address and continue to work. . 

6. Test

After this setting is completed, we can do a simple test first. We directly turn off the keepalived service on the master server, and then check whether there is a VIP address on the slave server, and it is successful. Let's start the keepalived service on the main server again to see if the VIP address has drifted to the main server again (test by ourselves)

Seven, the main server configuration WEB pool

[root@localhost keepalived]#vim keepalived.conf
Continue to add the following content under the original command configuration:
virtual_server 192.168.10.20 80 { #Virtual server VIP address and port
    delay_loop 6 #Interval time of health check (seconds)
    lb_algo rr #round-robin scheduling algorithm
    lb_kind DR #Direct routing cluster working mode
    persistence_timeout 50 #The connection retention time (seconds) can be added in front of it if it is not started (!)
    protocol TCP #Use the TCP protocol

    real_server 192.168.10.10 80 { #First WEB node address and port
        weight 1 #node weight
        TCP_CHECK { #Health check method
            connect_port 80 #Check directory port
            connect_timeout 3 #Connection timeout (seconds)
            nb_get_retry 3 #Number of retries
            delay_before_retry 3 #Retry interval (seconds)
        }

      }
real_server 192.168.10.10 8080 { #Address, port and partial information of the second web node
        weight 1
        TCP_CHECK {
            connect_port 8080
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
      }
    }
  }
[root@localhost keepalived]#service keepalived restart

Eight, configure the WEB pool from the server

[root@localhost keepalived]#vim keepalived.conf
#Continue to add the following content under the original command
virtual_server 192.168.10.20 80 {
    delay_loop 6
    lb_algo rr
    lb_kind DR
    persistence_timeout 50
    protocol TCP

    real_server 192.168.10.30 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }

      }
real_server 192.168.10.30 8080 {
        weight 1
        TCP_CHECK {
            connect_port 8080
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
      }
    }
  }
[root@localhost keepalived]#service keepalived restart

  9. Write scripts on the main service to achieve fully automated master-slave failover

[root@localhost ~]#vim /opt/keepalived.sh
#!/bin/bash
if [ `ps -C nginx --no-header |wc -l` -eq 0 ];
then
   /etc/init.d/keepalived stop
be
#Script means to detect Nginx service, if it is equal to 0, then stop keepalived directly
[root@localhost ~]#chmod +x /opt/keepalived.sh

 10. Apply the script to the keepalived configuration file of the main server  

[root@localhost keepalived]#vim keepalived.conf
.............
global_defs {
   router_id LVS_DEVEL_R1
}

vrrp_script chk_port { #Application script
    script "/opt/keepalived.sh"
    interval 2
    weight 2
}

.............
   authentication {
        auth_type PASS
        auth_pass 123456
    }

track_script { #tracking script
chk_port
 }
.............
.............

 11. Final Verification

We write different web page content in the master-slave web page. We can directly use the VIP address to access the web. Of course, the web page accessed first must be the master server, and the priority is high to determine who to visit first.
Now, in order to do the test, we can stop the Nginx service by hand, and then check the results, refresh the web page on the client machine, and we can see the web page content provided from the server. When the Nginx service of the main server is started, we need to start the keepalived service again, and the VIP address will return to the main server.