LVS + Keepalived 實現高可用負載均衡

$ sudo apt-get install ipvsadm keepalived
使用這兩個做配合時，無需配置 ipvsadm，直接修改 keepalived.conf 即可。

$ sudo vim /etc/keepalived/keepalived.conf

global_defs {
router_id LVS_DEVEL
}

vrrp_instance VI_1 {
state MASTER
interface eth0
virtual_router_id 51
priority 100
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 # 每隔 1 秒查詢 RealServer 狀態
lb_algo wrr # LVS 算法
lb_kind DR # Direct Route
#persistence_timeout 60 # 同一 IP 在 60 秒內分配到同一臺 RealServer
protocol TCP # 使用 TCP 協議檢查 RealServer 狀態

real_server 192.168.1.10 80 {
weight 3 # 權重
TCP_CHECK {
connect_timeout 10 # 10 秒無響應超時
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
}
}
}}
啟動 keepalived 服務。

$ sudo service keepalived start
檢查 ipvsadm 設置。

$ sudo ipvsadm -ln

IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler 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
在所有 RealServer /etc/rc.local 中添加配置信息后重啟。

$ 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
這時我們就可以用瀏覽器測試負載效果了。關閉某臺 RealServer，會發現請求被轉發給其他的 RealServer。重啟 "損壞" 的服務器后，負載均衡恢復正常。

(切記檢查防火墻設置，我為此郁悶了好長時間)

實驗環境: Ubuntu Server 10.04

------------ 分隔線 ------------

其實還應該找一臺服務器對 LVS 服務器做熱備(參見《Keepalived 雙機熱備》)，如此才是真正高可用方案。

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