2015年（68）
分类： LINUX
2015-08-31 17:11:24
介绍：
VRRP
VRRP（Virtual Router Redundancy Protocol）虚拟路由冗余协议将局域网的一组路由器（包括一个Master 即活动路由器和若干个Backup 即备份路由器）组织成一个虚拟路由器，并虚拟出一个IP（VIP），局域网内的主机知道这个虚拟路由器的IP 地址就可以了，不需要知道具体的Master 路由器的IP 地址以及Backup 路由器的IP 地址，它们将自己的缺省路由下一跳地址设置为该虚拟路由器的IP 地址并通过这个虚拟的路由器来与其它网络进行通信。如果备份组内的Master 路由器坏掉，Backup 路由器将会通过选举策略选出一个新的Master 路由器，继续向网络内的主机提供路由服务。从而实现网络内的主机不间断地与外部网络进行通信。关于VRRP 协议的详细信息，可以参考RFC 2338和这篇文章：http://www.cublog.cn/u/12313/showart_235796.html
KEEPALIVED
The main goal of the keepalived project is to add a strong & robust keepalive facility to the Linux Virtual Server project. This project is written in C with multilayer TCP/IP stack checks. Keepalived implements a framework based on three family checks : Layer3, Layer4 & Layer5/7. This framework gives the daemon the ability of checking a LVS server pool states. When one of the server of the LVS server pool is down, keepalived informs the linux kernel via a setsockopt call to remove this server entrie from the LVS topology. In addition keepalived implements an independent VRRPv2 stack to handle director failover. So in short keepalived is a userspace daemon for LVS cluster nodes healthchecks and LVS directors failover.
（选自）
简单说来就是keepalived是用来增强lvs服务器池中服务器的健康检查和故障隔离的，此外keepalived还实现了用 VRRPv2 stack 来处理节点的失败切换。
结构：
在我这个架构中，由于访问量不大，没有用到LVS，下面webserver的负载均衡是用nginx来做的，用keepalived的vrrp功能来做故障切换－〉在master 192.168.1.106出现故障时backup 192.168.1.107 接管vip并提供服务，在master正常情况下这个backup是用不到的。
VIP: 192.168.1.200
nginx1(master): 192.168.1.106
nginx2(backup): 192.168.1.107
webserver: 192.168.2.2/3/4
安装：
nginx:
[root@server1 ~]# ./configure --prefix=/usr/local/nginx
[root@server1 ~]# make && make install
keepalive:
[root@server1 ~]# yum install kernel-devel
[root@server1 ~]# wget
[root@server1 ~]# tar zxvf keepalived-1.2.1.tar.gz
[root@server1 ~]# cd keepalived-1.2.1
[root@server1 ~]# ./configure --prefix=/usr/local/keepalived --with-kernel-dir=/usr/src/kernels/2.6.18-238.9.1.el5-x86_64/
Keepalived configuration
------------------------
Keepalived version : 1.2.1
Compiler : gcc
Compiler flags : -g -O2 -DETHERTYPE_IPV6=0x86dd
Extra Lib : -lpopt -lssl -lcrypto
Use IPVS Framework : Yes
IPVS sync daemon support : Yes
Use VRRP Framework : Yes
Use Debug flags : No
[root@server1 ~]# make
[root@server1 ~]# make install
[root@server1 ~]# cp /usr/local/keepalived/sbin/keepalived /usr/sbin/
[root@server1 ~]# cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
[root@server1 ~]# cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/
[root@server1 ~]# mkdir /etc/keepalived
[root@server1 ~]# touch /etc/keepalived/keepalived.conf
配置：
nginx:
upstream solr {
server 192.168.2.2:80 weight=1 max_fails=3 fail_timeout=20s;
server 192.168.2.3:80 weight=1 max_fails=3 fail_timeout=20s;
server 192.168.2.4:80 weight=1 max_fails=3 fail_timeout=20s;
}
server {
listen 80;
server_name 172.16.2.7;
server_name_in_redirect off;
location / {
proxy_pass
}
}keepalive: master## global setting ##
global_defs {
router_id NGINX_FAILOVERE
}
## nginx check script ##
vrrp_script chk_nginx {
script "/opt/mytools/chk_nginx.sh"
interval 10
}
## vrrp setting ##
vrrp_instance VI_1 {
state MASTER
interface bond0
virtual_router_id 51
mcast_src_ip 192.168.1.106
priority 150
advert_int 5
authentication {
auth_type PASS
auth_pass imusic
}
track_script {
chk_nginx
}
virtual_ipaddress {
192.168.1.200
}
}
keepalive: backup
## global setting ##
global_defs {
router_id NGINX_FAILOVERE
}
## nginx check script ##
vrrp_script chk_nginx {
script "/opt/mytools/chk_nginx.sh"
interval 10
}
## vrrp setting ##
vrrp_instance VI_1 {
state BACKUP
interface bond0
virtual_router_id 51
mcast_src_ip 192.168.1.107
priority 130
advert_int 5
authentication {
auth_type PASS
auth_pass imusic
}
track_script {
chk_nginx
}
virtual_ipaddress {
192.168.1.200
}
}
nginx的配置没什么好说的，只是想做两个节点间的故障切换，所以keepalived 只要配置VRRP就可以了，主备配置不同的地方只有红色加粗的那些。
另外比较重要的是vrrp_script和track_script，track_script指定检查脚本，/opt/mytools/chk_nginx.sh的功能是检查本机nginx的状态，nginx服务死了则将它重启，如果重启失败就将keepalived停掉让另一台keepalived接管VIP，这样做是为了避免keepalived没有死而nginx死掉时发生的单点故障，如master 192.168.1.106上的keepalived运行正常而nginx没有启动，这时是不能成功访问的。
使用：
[root@server1 ~]# /etc/init.d/keepalived start #启动
[root@server1 ~]# ip add #可以看到VIP 192.168.1.200已经绑到了网卡bond0
7: bond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 1500 qdisc noqueue
link/ether 00:26:55:83:e2:10 brd ff:ff:ff:ff:ff:ff
inet 192.168.1.106/24 brd 192.168.1.255 scope global bond0
inet 192.168.1.200/32 scope global bond0
inet6 fe80::226:55ff:fe83:e210/64 scope link
valid_lft forever preferred_lft forever
附：
vrrp_script配置参数
script 脚本名或命令
interval 脚本执行间隔，隔多久执行一次，单位为秒
weight -40 #if failed, decrease 40 of the priority
fall 1 #require 2 failures for failures
rise 1 #equire 1 sucesses for ok
chk_nginx.sh 脚本内容：
#!/bin/sh
# check nginx server status
Nginx=/usr/local/nginx/sbin/nginx
NginxPort=80
Nmap=/usr/bin/nmap
Server=localhost
$Nmap $Server -p $NginxPort |grep "$NginxPort/tcp open"
if [ $? -ne 0 ];then
$Nginx
sleep 2
$Nmap $Server -p $NginxPort |grep "$NginxPort/tcp open"
[ $? -ne 0 ] && /etc/init.d/keepalived stop
fi
