LVS簡介：
LVS集羣有DR、TUN、NAT三種配置模式，可以對www服務、FTP服務、MAIL服務等做負載均衡，下面通過搭建www服務的負載均衡實例，講述基於DR模式的LVS集羣配置
Director-Server: LVS的核心服務器，作用類似於一個路由器，含有爲LVS功能完成的路由表，通過路由表把用戶的請求分發給服務器組層的應用服務器（Real_Server),同時監控Real-servers
，在Real-Server不可用時，將其從LVS路由表中剔除，再恢復時，重新加入。
Real-Server:由web服務器，mail服務器，FTP服務器，DNS服務器，視頻服務器中的一個或多個，每個Real-Server通過LAN分佈或WAN分佈相連接。實際過程中DR，也可以同時兼任Real-server
LVS的三種負載均衡方式：
NAT：調度器將請求的目標地址和目標端口，改寫成Real-server的地址和端口，然後發送到選定的Real-server上，Real-Server端將數據返回給用戶時，需要再次經過DR將報文的源地址和源端口改成虛擬IP的地址和端口，然後把數據發送給用戶，完成整個負載調度過程。
弊端：調度器負載大
TUN: IP隧道方式，調度器將請求通過IP隧道轉發到Real-server，而Real-server直接響應用戶的請求，不再經調度器。D與R可不同網絡，TUN方式中，調度器將只處理用戶的報文請求，提高吞吐量。
弊端：有IP隧道開銷
DR：直接路由技術實現虛擬服務器，DR通過改寫請求的MAC，將請求發送給Real-server，而Real-server直接響應給Client，免去了隧道開銷。三種方式中，效果最好。
弊端：要求D與R同在一個物理網段
LVS的負載調度方式：
LVS是根據Real-Server的負載情況，動態的選擇Real-server響應，IPVS實現了8種負載調度算法，這裏講述4種調度算法：
rr 輪叫調度：
平等分配R，不考慮負載。
wrr 加權輪叫調度：
設置高低權值，分配給R。
lc 最少連接調度：
動態分配給已建立連接少的R上。
wlc 加權最少連接調度：
動態的設置R的權值，在分配新連接請求時，儘可能使R的已建立連接和R的權值成正比。
環境介紹：
本例使用三臺主機，一臺Director-server（調度服務器），兩臺web real_server（web服務器）
DS的真實IP：10.2.16.250
VIP：10.2.16.252
RealServer——1 的真實IP： 10.2.16.253
RealServer——2 的真實IP： 10.2.16.254
注意：本例採用LVS的DR模式，使用rr輪詢來做負載均衡
用keepalived方式安裝配置LVS
1、安裝keepalived
[root@proxy ~]# tar -zxvf keepalived-1.2.13.tar.gz -C ./
[root@proxy ~]# cd keepalived-1.2.13
[root@proxy keepalived-1.2.13]# ./configure --sysconf=/etc/ --with-kernel-dir=/usr/src/kernels/2.6.32-358.el6.x86_64/
[root@proxy keepalived-1.2.13]# make && make install
[root@proxy keepalived-1.2.13]# ln /usr/local/sbin/keepalived /sbin/
2、安裝LVS
yum -y install ipvsadm*
開啓路由轉發功能：
[root@proxy ~]# vim /etc/sysctl.conf
net.ipv4.ip_forward = 1
[root@proxy ~]# sysctl -p
3、在調度服務器上配置keepalived和LVS
[root@proxy ~]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
notification_email {
}
notification_email_from [email protected]
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id LVS_DEVEL
}
vrrp_instance VI_1 {
state MASTER
interface eth0 #LVS的真實物理網卡
virtual_router_id 51
priority 100
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress { #LVS的VIP
10.2.16.252
}
}
virtual_server 10.2.16.252 80 { #定義對外提供服務的LVS的VIP以及port
delay_loop 6 #設置運行情況檢查時間，單位是s
lb_algo rr #設置負載調度算法，RR爲輪詢調度
lb_kind DR #設置LVS的負載均衡機制，NAT/TUN/DR 三種模式
nat_mask 255.255.255.0
# persistence_timeout 50 #會話保持時間，單位是s，對動態網頁的session共享有用
protocol TCP #指定轉發協議類型
real_server 10.2.16.253 80 { #指定realserver的真實IP和port
weight 1 #設置權值，數字越大分配的機率越高
TCP_CHECK { #realserver的狀態檢測部分
connect_timeout 3 #表示3秒無響應超時
nb_get_retry 3 #重試次數
delay_before_retry 3 #重試間隔
}
}
real_server 10.2.16.254 80 { #配置服務節點2
weight 1
TCP_CHECK {
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
}
}
}
4、配置Real_Server
由於採用的是DR方式調度，Real_Server會以LVS的VIP來直接回復Client，所以需要在Real_Server的lo上開啓LVS的VIP來與Client建立通信
1、此處寫了一個腳本來實現VIP這項功能：
[root@web-1 ~]# cat /etc/init.d/lvsrs
#!/bin/bash
#description : start Real Server
VIP=10.2.16.252
./etc/rc.d/init.d/functions
case "$1" in
start)
echo " Start LVS of Real Server "
/sbin/ifconfig lo:0 $VIP broadcast $VIP netmask 255.255.255.255 up
/sbin/route add -host $VIP dev lo:0
echo "1" >/proc/sys/net/ipv4/conf/lo/arp_ignore #註釋：這四句目的是爲了關閉ARP廣播響應，使VIP不能向網絡內發送廣播，以防止網絡出現混亂
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
;;
stop)
/sbin/ifconfig lo:0 down
echo "close LVS Director server"
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 "Usage: $0 {start|stop}"
exit 1
esac
2、啓動腳本：
[root@web-1 ~]# service lvsrs start
Start LVS of Real Server
3、查看lo:0虛擬網卡的IP：
[root@web-1 ~]# ifconfig
eth0 Link encap:Ethernet HWaddr 00:0C:29:A2:C4:9F
inet addr:10.2.16.253 Bcast:10.2.16.255 Mask:255.255.255.0
inet6 addr: fe80::20c:29ff:fea2:c49f/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:365834 errors:0 dropped:0 overruns:0 frame:0
TX packets:43393 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:33998241 (32.4 MiB) TX bytes:4007256 (3.8 MiB)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:17 errors:0 dropped:0 overruns:0 frame:0
TX packets:17 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:1482 (1.4 KiB) TX bytes:1482 (1.4 KiB)
lo:0 Link encap:Local Loopback
inet addr:10.2.16.252 Mask:255.255.255.255
UP LOOPBACK RUNNING MTU:16436 Metric:1
4、確保nginx訪問正常
[root@web-1 ~]# netstat -anptul
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN 1024/nginx
5、在real_server2上，執行同樣的4步操作。
6、開啓DR上的keepalived：
[root@proxy ~]# service keepalived start
Starting keepalived: [ OK ]
查看keepalived啓動日誌是否正常：
[root@proxy ~]# tail -f /var/log/messeges
May 24 10:06:57 proxy Keepalived[2767]: Starting Keepalived v1.2.13 (05/24,2014)
May 24 10:06:57 proxy Keepalived[2768]: Starting Healthcheck child process, pid=2770
May 24 10:06:57 proxy Keepalived[2768]: Starting VRRP child process, pid=2771
May 24 10:06:57 proxy Keepalived_healthcheckers[2770]: Netlink reflector reports IP 10.2.16.250 added
May 24 10:06:57 proxy Keepalived_vrrp[2771]: Netlink reflector reports IP 10.2.16.250 added
May 24 10:06:57 proxy Keepalived_healthcheckers[2770]: Netlink reflector reports IP fe80::20c:29ff:fee6:ce1a added
May 24 10:06:57 proxy Keepalived_healthcheckers[2770]: Registering Kernel netlink reflector
May 24 10:06:57 proxy Keepalived_healthcheckers[2770]: Registering Kernel netlink command channel
May 24 10:06:57 proxy Keepalived_vrrp[2771]: Netlink reflector reports IP fe80::20c:29ff:fee6:ce1a added
May 24 10:06:57 proxy Keepalived_vrrp[2771]: Registering Kernel netlink reflector
May 24 10:06:57 proxy Keepalived_vrrp[2771]: Registering Kernel netlink command channel
May 24 10:06:57 proxy Keepalived_vrrp[2771]: Registering gratuitous ARP shared channel
May 24 10:06:57 proxy Keepalived_vrrp[2771]: Opening file '/etc/keepalived/keepalived.conf'.
May 24 10:06:57 proxy Keepalived_vrrp[2771]: Configuration is using : 63303 Bytes
May 24 10:06:57 proxy Keepalived_vrrp[2771]: Using LinkWatch kernel netlink reflector...
May 24 10:06:57 proxy Keepalived_healthcheckers[2770]: Opening file '/etc/keepalived/keepalived.conf'.
May 24 10:06:57 proxy Keepalived_healthcheckers[2770]: Configuration is using : 14558 Bytes
May 24 10:06:57 proxy Keepalived_vrrp[2771]: VRRP sockpool: [ifindex(2), proto(112), unicast(0), fd(10,11)]
May 24 10:06:57 proxy Keepalived_healthcheckers[2770]: Using LinkWatch kernel netlink reflector...
May 24 10:06:57 proxy Keepalived_healthcheckers[2770]: Activating healthchecker for service [10.2.16.253]:80
May 24 10:06:57 proxy Keepalived_healthcheckers[2770]: Activating healthchecker for service [10.2.16.254]:80
May 24 10:06:58 proxy Keepalived_vrrp[2771]: VRRP_Instance(VI_1) Transition to MASTER STATE
May 24 10:06:59 proxy Keepalived_vrrp[2771]: VRRP_Instance(VI_1) Entering MASTER STATE
May 24 10:06:59 proxy Keepalived_vrrp[2771]: VRRP_Instance(VI_1) setting protocol VIPs.
May 24 10:06:59 proxy Keepalived_vrrp[2771]: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 10.2.16.252
May 24 10:06:59 proxy Keepalived_healthcheckers[2770]: Netlink reflector reports IP 10.2.16.252 added
May 24 10:07:04 proxy Keepalived_vrrp[2771]: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 10.2.16.252
一切正常！
7、查看LVS的路由表：
[root@proxy ~]# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 10.2.16.252:80 rr
-> 10.2.16.253:80 Route 1 0 0
-> 10.2.16.254:80 Route 1 0 0
8、測試，打開網頁，輸入 http://10.2.16.252/
能正常出現兩臺負載均衡服務器的網頁，則證明已經成功！
9、測試其中一臺Real-Server服務掛掉
（1）把254的nginx進程殺掉，再開啓。
（2）查看keepalived的日誌：
[root@proxy ~]#tail -f /var/log/messeges
May 24 10:10:55 proxy Keepalived_healthcheckers[2770]: TCP connection to [10.2.16.254]:80 failed !!!
May 24 10:10:55 proxy Keepalived_healthcheckers[2770]: Removing service [10.2.16.254]:80 from VS [10.2.16.252]:80
May 24 10:10:55 proxy Keepalived_healthcheckers[2770]: Remote SMTP server [127.0.0.1]:25 connected.
May 24 10:10:55 proxy Keepalived_healthcheckers[2770]: SMTP alert successfully sent.
May 24 10:11:43 proxy Keepalived_healthcheckers[2770]: TCP connection to [10.2.16.254]:80 success.
May 24 10:11:43 proxy Keepalived_healthcheckers[2770]: Adding service [10.2.16.254]:80 to VS [10.2.16.252]:80
May 24 10:11:43 proxy Keepalived_healthcheckers[2770]: Remote SMTP server [127.0.0.1]:25 connected.
May 24 10:11:43 proxy Keepalived_healthcheckers[2770]: SMTP alert successfully sent.
可見keepalive的反應速度還是非常快的！
到此，LVS配置全部結束，圓滿成功！