作者:NetSeek http://www.linuxtone.org(IT運維專家網|集羣架構|性能調優)
更新時間:2008-10-27
文章來源：http://bbs.linuxtone.org/thread-1077-1-1.html
背景:
隨着你的網站業務量的增長你網站的服務器壓力越來越大？需要負載均衡方案！商業的硬件如F5又太貴，你們又是創業型互聯公司如何有效節約成本，節省不必要的浪費？同時實現商業硬件一樣的高性能高可用的功能？有什麼好的負載均衡可伸張可擴展的方案嗎？答案是肯定的！有！我們利用LVS+Keepalived基於完整開源軟件的架構可以爲你提供一個負載均衡及高可用的服務器。
LVS+Keepalived 介紹
LVS
LVS是Linux Virtual Server的簡寫，意即Linux虛擬服務器，是一個虛擬的服務器集羣系統。本項目在1998年5月由章文嵩博士成立，是中國國內最早出現的自由軟件項目之一。目前有三種IP負載均衡技術（VS/NAT、VS/TUN和VS/DR）；
十種調度算法（rrr|wrr|lc|wlc|lblc|lblcr|dh|sh|sed|nq）。
Keepalvied
Keepalived在這裏主要用作RealServer的健康狀態檢查以及LoadBalance主機和BackUP主機之間failover的實現
二. 網站負載均衡拓樸圖
IP信息列表：
名稱 IP
LVS-DR-BACKUP 61.164.122.7
LVS-DR-VIP 61.164.122.8
WEB1-Realserver 61.164.122.9
WEB2-Realserver 61.164.122.10
GateWay 61.164.122.1
三. 安裝LVS和Keepalvied軟件包
1. 下載相關軟件包
#cd /usr/local/src/lvs
#wget http://www.linuxvirtualserver.org/software/kernel-2.6/ipvsadm-1.24.tar.gz
#wget http://www.keepalived.org/software/keepalived-1.1.15.tar.gz
2. 安裝LVS和Keepalived
#uname -r
2.6.18-53.el5PAE
#ln -s /usr/src/kernels/2.6.18-53.el5PAE-i686//usr/src/linux
#tar zxvf ipvsadm-1.24.tar.gz
#cd ipvsadm-1.24
#make && make install
#find / -name ipvsadm# 查看ipvsadm的位置
#tar zxvf keepalived-1.1.15.tar.gz
#cd keepalived-1.1.15
#./configure&& make && make install
#find / -name keepalived# 查看keepalived位置
#cp /usr/local/etc/rc.d/init.d/keepalived /etc/rc.d/init.d/
#cp /usr/local/etc/sysconfig/keepalived /etc/sysconfig/
#mkdir /etc/keepalived
#cp /usr/local/etc/keepalived/keepalived.conf /etc/keepalived/
#cp /usr/local/sbin/keepalived /usr/sbin/
#service keepalived start|stop #做成系統啓動服務方便管理.
四. 配置LVS實現負載均衡
1． LVS-DR，配置LVS腳本實現負載均衡
注: 此腳本在於演示方便大家理解lvs,在keepalived方案中不要啓動此腳本，所以看後面有注掉，很多朋友對此有問題。關於LVS的keepalvied的HA方案，完全由keepalived.conf一個文件搞定，特此聲明！
#!/bin/bash
# description: start LVS of DirectorServer
#Written by :NetSeek http://www.linuxtone.org
GW=61.164.122.1
# website director vip.
SNS_VIP=61.164.122.8
SNS_RIP1=61.164.122.9
SNS_RIP2=61.164.122.10
./etc/rc.d/init.d/functions
logger $0 called with $1
case "$1" in
start)
# set squid vip
/sbin/ipvsadm --set 30 5 60
/sbin/ifconfig eth0:0 $SNS_VIP broadcast $SNS_VIP netmask 255.255.255.255 broadcast $SNS_VIP up
/sbin/route add -host $SNS_VIP dev eth0:0
/sbin/ipvsadm -A -t $SNS_VIP:80 -s wrr -p 3
/sbin/ipvsadm -a -t $SNS_VIP:80 -r $SNS_RIP1:80 -g -w 1
/sbin/ipvsadm -a -t $SNS_VIP:80 -r $SNS_RIP2:80 -g -w 1
touch /var/lock/subsys/ipvsadm >/dev/null 2>&1
;;
stop)
/sbin/ipvsadm -C
/sbin/ipvsadm -Z
ifconfig eth0:0 down
route del $SNS_VIP
rm -rf /var/lock/subsys/ipvsadm >/dev/null 2>&1
echo "ipvsadm stoped"
;;
status)
if [ ! -e /var/lock/subsys/ipvsadm ];then
echo "ipvsadm stoped"
exit 1
else
echo "ipvsadm OK"
fi
;;
*)
echo "Usage: $0 {start|stop|status}"
exit 1
esac
exit 0
2． 配置Realserver腳本.
#!/bin/bash
# description: Config realserver lo and apply noarp
#Written by :NetSeek http://www.linuxtone.org
SNS_VIP=61.164.122.8
. /etc/rc.d/init.d/functions
case "$1" in
start)
ifconfig lo:0 $SNS_VIP netmask 255.255.255.255 broadcast $SNS_VIP
/sbin/route add -host $SNS_VIP dev lo:0
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
sysctl -p >/dev/null 2>&1
echo "RealServer Start OK"
;;
stop)
ifconfig lo:0 down
route del $SNS_VIP >/dev/null 2>&1
echo "0" >/proc/sys/net/ipv4/conf/lo/arp_ignore
echo "0" >/proc/sys/net/ipv4/conf/lo/arp_announce
echo "0" >/proc/sys/net/ipv4/conf/all/arp_ignore
echo "0" >/proc/sys/net/ipv4/conf/all/arp_announce
echo "RealServer Stoped"
;;
*)
echo "Usage: $0 {start|stop}"
exit 1
esac
exit 0
或者採用secondary ip address方式配置
# vi /etc/sysctl.conf
net.ipv4.conf.lo.arp_announce = 2
net.ipv4.conf.all.arp_ignore = 1
net.ipv4.conf.all.arp_announce = 2
[code]
#sysctl ?p
#ip addr add 61.164.122.8/32 dev lo
#ip add list 查看是否綁定
3. 啓動lvs-dr腳本和realserver啓本，在DR上可以查看LVS當前狀態:
#watch ipvsadm ?ln
五．利用Keepalvied實現負載均衡和和高可用性
1.配置在主負載均衡服務器上配置keepalived.conf
#vi /etc/keepalived/keepalived.conf
global_defs {
notification_email {
[email protected]
}
notification_email_from [email protected]
smtp_server 127.0.0.1
# smtp_connect_timeout 30
router_id LVS_DEVEL
}
# 20081013 written by :netseek
# VIP1
vrrp_instance VI_1 {
state MASTER #備份服務器上將MASTER改爲BACKUP
interface eth0
virtual_router_id 51
priority 100 # 備份服務上將100改爲99
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
61.164.122.8
#(如果有多個VIP，繼續換行填寫.)
}
}
virtual_server 61.164.122.8 80 {
delay_loop 6 #(每隔10秒查詢realserver狀態)
lb_algo wrr #(lvs 算法)
lb_kind DR #(Direct Route)
persistence_timeout 60 #(同一IP的連接60秒內被分配到同一臺realserver)
protocol TCP #(用TCP協議檢查realserver狀態)
real_server 61.164.122.9 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 61.164.122.10 80 {
weight 3
TCP_CHECK {
connect_timeout 10
nb_get_retry 3
delay_before_retry 3
connect_port 80
}
}
}
2. BACKUP服務器同上配置，先安裝lvs再按裝keepalived,仍後配置/etc/keepalived/keepalived.conf，只需將紅色標示的部分改一下即可.
3. 停掉lvs_dr.sh演示腳本
vi /etc/rc.local
#/usr/local/sbin/lvs-dr.sh將lvs-dr.sh這個腳本註釋掉。
#/usr/local/sbin/lvs-dr.sh stop 停止lvs-dr腳本
#/etc/init.d/keepalived start啓動keepalived 服務，keepalived就能利用keepalived.conf 配置文件，實現負載均衡和高可用.
整個LVS負均衡HA方案，由keepalived.conf一個文件即可搞定！
4. 查看lvs服務是否正常
#watch ipvsadm ?ln
Prot LocalAddressort Scheduler Flags
-> RemoteAddressort Forward Weight ActiveConn InActConn
TCP61.164.122.8:80 wrr persistent 60
-> 61.164.122.10:80 Route 3 0 0
-> 61.164.122.9:80 Route 3 0 0
#tail ?f /var/log/message監聽日誌，查看狀態，測試LVS負載均衡及高可用性是否有效。
5．停Master服務器的keepalived服務，查看BAKCUP服務器是否能正常接管服務。
四．相關參考
1．LVS 基礎知識彙總
LVS的算法介紹 http://bbs.linuxtone.org/viewthread.php?tid=69
學習LVS的三種轉發模式 http://bbs.linuxtone.org/viewthread.php?tid=77
LVS中的IP負載均衡技術 http://bbs.linuxtone.org/viewthread.php?tid=68
更多的請到http://www.linuxtone.org 負載均衡版查看
Keepalived 相關參考資料。
http://www.keepalived.org/documentation.html
提供DOC文檔下載:
PDF下載： http://docs.linuxtone.org/ebooks/load%20balance/lvs/
