LVS + Keepalived for high-availability Load Balancing

Although LVS implements load balancing, it cannot solve a serious problem. When a RealServer is on the machine, it cannot direct subsequent requests allocated to the server to other surviving servers.

$ Sudo apt-get install ipvsadm keepalived
You can directly modify keepalived. conf without configuring ipvsadm.

$ Sudo vim/etc/keepalived. conf

Global_defs {
Router_id LVS_DEVEL
}

Vrrp_instance VI_1 {
State MASTER
Interface eth0
Virtual_router_id 51
Priority100
Advert_int 1

Authentication {
Auth_type PASS
Auth_pass 1111
}

Virtual_ipaddress {
192.168.1.100
}
}

Virtual_server 192.168.1.100 80 {
Delay_loop 1 # query RealServer status every 1 second
Lb_algo wrr # LVS Algorithm
Lb_kind DR # Direct Route
# Persistence_timeout 60 # the same IP address is allocated to the same RealServer within 60 seconds.
Protocol TCP # Use the TCP protocol to check the RealServer status

Real_server 192.168.1.10 80 {
Weight 3 # weight
TCP_CHECK {
Connect_timeout 10 # No response timeout in 10 seconds
Nb_get_retry 3
Delay_before_retry 3
Connect_port 80
}
}

Real_server 192.168.1.20 80 {
Weight 3
TCP_CHECK {
Connect_timeout 10
Nb_get_retry 3
Delay_before_retry 3
Connect_port 80
}
}
}}
Start the keepalived service.

$ Sudo service keepalived start
Check ipvsadm settings.

$ Sudo ipvsadm-ln

IP Virtual Server version 1.2.1 (size = 4096)
Prot LocalAddress: Port sched1_flags
-> RemoteAddress: Port Forward Weight ActiveConn InActConn
TCP 192.168.1.100: 80 wrr
-> 192.168.1.10: 80 Route 3 0 0
-> 192.168.1.20: 80 Route 3 0 0
Add configuration information to all RealServer/etc/rc. local and restart.

$ Sudo vim/etc/rc. local

#! /Bin/sh-e
#
# Rc. local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# Value on error.
#
# In order to enable or disable this script just change the execution
# Bits.
#
# By default this script does nothing.

Ifconfig lo: 0 192.168.1.100 netmask 255.255.255.255 broadcast 192.168.1.100 up
Route add-host 192.168.1.100 dev lo: 0

Echo "0">/proc/sys/net/ipv4/ip_forward
Echo "1">/proc/sys/net/ipv4/conf/lo/arp_ignore
Echo "2">/proc/sys/net/ipv4/conf/lo/arp_announce
Echo "1">/proc/sys/net/ipv4/conf/all/arp_ignore
Echo "2">/proc/sys/net/ipv4/conf/all/arp_announce

Exit 0
Then we can use a browser to test the load effect. Shut down a RealServer and you will find that the request is forwarded to another RealServer. After the "damaged" server is restarted, the Server Load balancer returns to normal.

(Check the firewall settings. I have been depressed for a long time)

Lab environment: Ubuntu Server 10.04

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In fact, we should also find a server to perform hot backup on the LVS server (see Keepalived dual-host Hot Backup). This is the real high-availability solution.