keepalived入门之nginx高可用部署 (应用篇)
我们常常遇到这样一些应用环境：客户端通过访问nginx，nginx再通过反向代理将后端web server运行的业务反馈给客户端，但是如果nginx server出现宕机或者其他bug导致业务不能正常运营，所以为了不影响业务正常运营，我们引进了keepalive+nginx组合，来保证整个系统的高可用。Keepalive+Nginx双机热备
如图所示为整体的拓扑图：
一.部署前说明：
(1)系统版本: centos 6.6（64位）
(2)角色及ip相关信息:
角色名称网络ip信息客户端(CIP)10.58.137.203/24Master_DReth0:172.51.96.105/24 &ð1:192.168.0.105/24Backup_DReth0:172.51.96.119/24 &ð1:192.168.0.119/24VIP172.51.96.175/32 (3)相关中间件信息
keepalive版本信息: keepalived-1.2.15
nginx版本信息: nginx1.6.0（提供http服务）
二.部署操作：
负载均衡器上配置操作
nginx部署：
分别在Master_DR和backup_DR上安装nginx，操作如下：
1.1相关系统依赖包安装检查准备
1.2.1 检查系统自带nginx是否安装
rpm -qa | grep nginx 如有安装，请使用以下命令卸载相关程序
yum remove nginx -y 1.2.2 安装编译nginx需要的依赖包
yum install gcc openssl-devel pcre-devel zlib-devel -y 2.1.1到nginx官网下载nginx软件，如下所示：
cd ~ wget
http://nginx.org/download/nginx-1.8.0.tar.gz 2.1.2 添加运行nginx服务账号
groupadd -r nginx useradd -r -g nginx -s /bin/false -M nginx
2.1.3 解压编译安装nginx
cd ~ tar -zxf /root/nginx-1.8.0.tar.gz -C /usr/local/src
./configure \
--prefix=/usr/local/nginx \
--sbin-path=/usr/local/nginx/sbin/nginx \
--conf-path=/etc/nginx/nginx.conf\
--error-log-path=/var/log/nginx/error.log \
--http-log-path=/var/log/nginx/access.log\
--pid-path=/var/run/nginx/nginx.pid\
--lock-path=/var/lock/nginx.lock \
--user=nignx \
--group=nginx \
--with-http_ssl_module \
--with-http_stub_status_module \
--with-http_gunzip_module \
--with-http_gzip_static_module \
--http-client-body-temp-path=/var/tmp/nginx/client/ \
--http-proxy-temp-path=/var/tmp/nginx/proxy/ \
--http-fastcgi-temp-path=/var/tmp/nginx/fastcgi/ \
--http-uwsgi-temp-path=/var/tmp/nginx/uwsgi/ \
--http-scgi-temp-path=/var/tmp/nginx/scgi/ \
--with-pcre
make && make install
2.1.4 使用sed修改nginx的配置文件，指定nginx的运行用户
sed'3 iuser nginx;' -i /etc/nginx/nginx.conf 修改后，nginx主配置文件内容如下
注意：不修改nginx的运行用户的话，会报如下错误，如下图所示，
2.1.5 启动nginx服务
/usr/local/nginx/sbin/nginx 下面就可访问nginx的主页面了，如下：
至此，nginx部署就基本OK了！
注：关于nginx服务方式启动脚本示例请访问：http://blief.blog.51cto.com/6170059/1690492
Keepalive部署
(1)分别在Master_DR和backup_DR上安装keepalive，操作如下：
1. 安装Keepalive所需要的相关依赖包:
# yum install openssl-devel popt-devel libnl-devel kernel-devel-y 2. 编译安装keepalive
1.1 keepalived的源码获取
keepalived源码包我们可以到keepalived的官网:http://www.keepalived.org/去下载，相关说明文档亦可在其官网查看，比如keepalived的使用，相关配置说明，这里演示的版本为:1.2.15
# cd ~ # wget http://www.keepalived.org/software/keepalived-1.2.15.tar.gz
1.2 编译安装keepalived
# ln -s /usr/src/kernels/2.6.32-573.18.1.el6.x86_64/ /usr/src/linux # tar zxvf keepalived-1.2.15.tar.gz -C /usr/local/src
# cd /usr/local/src/keepalived-1.2.15/
# ./configure \
--prefix=/usr/local/keepalived \
--with-kernel-dir=/usr/src/kernels/2.6.32-573.18.1.el6.x86_64
# makemake install
# cp /usr/local/keepalived/sbin/keepalived /usr/sbin/
# cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
# cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/
# chkconfig --add keepalived
# chkconfig --level 2345 keepalived on
# mkdir -p /etc/keepalived
# cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived
(3)分别配置Master_DR以及Backup_DR上的keepalive实例，如下所示:
1. Lvs_master_dr配置代码示例（主调度器）
vim /etc/keepalived/keepalived.conf 内容如下
! Configuration File for keepalived
global_defs {
notification_email {
admin@bluemobi.cn
}
notification_email_fromlvs_admin@bluemobi.cn
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id DR_MASTER
}
vrrp_script check_nginx { #表示创建一个脚本check_nginx
script "/etc/keepalived/scripts/check_nginx.sh" #引用的脚本路径
interval 3 #表示检测时间的间隔为3s
}
vrrp_instance http {
state BACKUP
interface eth0
lvs sync daemon interface eth0 #类似HA心跳检测的端口
dont_track_primary
nopreempt #不抢占master
track_interface { #表示需要检测的网卡
eth0
eth1
}
mcast_src_ip 172.51.96.105 #表示设置组播的源地址
garp_master_delay 6
virtual_router_id 60
priority 110
advert_int 1
authentication {
auth_type PASS
autp_pass 1234
}
virtual_ipaddress {
172.51.96.175/24 brd172.51.96.255 dev eth0 label eth0:1
}
virtual_routes {
172.51.96.175/24 dev eth0
}
track_script {
check_nginx
}
notify_master /etc/keepalived/scripts/state_master.sh
notify_backup /etc/keepalived/scripts/state_backup.sh
notify_fault/etc/keepalived/scripts/state_fault.sh
}
2 Lvs_backup_dr配置示例（备调度器）
vim /etc/keepalived/keepalived.conf 内容如下
! Configuration File for keepalived
global_defs {
notification_email {
admin@bluemobi.cn
}
notification_email_fromlvs_admin@bluemobi.cn
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id DR_BACKUP
}
vrrp_script check_nginx {
script "/etc/keepalived/scripts/check_nginx.sh"
interval 3
}
vrrp_instance http {
state BACKUP
interface eth0
lvs sync daemon interface eth0
dont_track_primary
track_interface {
eth0
eth1
}
mcast_src_ip 172.51.96.119
garp_master_delay 6
virtual_router_id 60
priority 105
advert_int 1
authentication {
auth_type PASS
autp_pass 1234
}
virtual_ipaddress {
172.51.96.175/24 brd172.51.96.255 dev eth0 label eth0:1
}
virtual_routes {
172.51.96.175/24 dev eth0
}
track_script {
check_nginx
}
notify_master /etc/keepalived/scripts/state_master.sh
notify_backup /etc/keepalived/scripts/state_backup.sh
notify_fault/etc/keepalived/scripts/state_fault.sh
}
3.分别在主调度server和备调度server编写以下脚本，如下：
i 当调度器为切换master server时，记录切换时间日志
vim /etc/keepalived/scripts/state_master.sh
代码如下:
#!/bin/bash
echo -e>> $LOGFILE
host=CN-SH-DR01 #设置当前的主机名
LOGFILE="/var/log/keepalived-state.log"
echo "" >> $LOGFILE
date >> $LOGFILE
echo "The ${host}Starting to become master server...." >> $LOGFILE 2>&1
echo "Please run the “ipvsadm -Ln”check the keepalived state ..." >> $LOGFILE
echo ".........................................................................!">> $LOGFILE
echo >>$LOGFILE
ii 当调度器为切换backup server时，记录切换时间日志
vim /etc/keepalived/scripts/state_backup.sh
代码如下:
#!/bin/bash
echo -e >> $LOGFILE
host=CN-SH-DR01 #设置当前的主机名
LOGFILE="/var/log/keepalived-state.log"
echo "" >> $LOGFILE
date >> $LOGFILE
echo "The ${host}Starting to become Backup server...." >> $LOGFILE 2>&1
echo "Please run the “ipvsadm -Ln”check the state ..." >> $LOGFILE
echo "........................................................................!">> $LOGFILE
echo>> $LOGFILE
iii当调度器出现错误时，记录错误时间日志
vim /etc/keepalived/scripts/state_fault.sh
代码如下:
#!/bin/bash
echo -e >> $LOGFILE
host=CN-SH-DR01 #设置当前的主机名
LOGFILE="/var/log/keepalived-state.log"
echo "" >> $LOGFILE
date >> $LOGFILE
echo "The ${host}is fault error...." >> $LOGFILE 2>&1
echo "Please check the server state ..." >> $LOGFILE
echo "........................................................................!">> $LOGFILE
echo>> $LOGFILE
iiii 服务状态健康监测脚本,比如当nginx不可用时，及时切换到backup调度器上
vim /etc/keepalived/scripts/check_nginx.sh
#!/bin/bash
#nginx="/usr/local/nginx/sbin/nginx"
PID=`ps -C nginx --no-heading|wc -l`
if [ "${PID}" = "0" ];
then
/etc/init.d/nginx start
sleep 3
LOCK=`ps -C nginx --no-heading|wc -l`
if [ "${LOCK}" = "0" ];
then
/etc/init.d/keepalived stop
fi
fi
(4)依次重启master_dr,backup-dr上keepalive服务
# service keepalived restart
三.测试验证：
在两台调度器创建相关测试页，如下：
master-dr主调度服务器的测试页面
# curl 172.51.96.105
this is master server
#
backup-dr主调度服务器的测试页面
# curl 127.0.0.1
this is backup server
#
通过messages查看vip抢夺情况，如下所示:
述上发现vip已经被master-dr抢夺，通过ifconfig看到master-dr已经存在vip地址，如下
在客户端通过:http://vip 就可以访问到页面，此时访问的是master-dr的页面：
将nginx的启动命令:/usr/local/nginx/sbin/nginx命名为：/usr/local/nginx/sbin/nginx1,再关闭nginx来模仿nginx服务故障
分别查看master-dr和backup-dr的keepalive日志：
此时vip已经由backup-dr接管了，因为master-dr上nginx服务异常，而keepalive会定时触发引用的检查脚本“check_nginx”检查nginx状态，发现nginx可用就停止了keepalive服务，从而使vip顺利的飘逸到backup-dr上；
查看keepalive-state.log,可以看到master-dr和backup-dr会记录每个状态的的信息：同时日志记录脚本也会记录相关信息：
# tail -10/var/log/keepalived-state.log
The CN-SH-DR01Starting to become Backup server....
Please run the “ipvsadm -Ln”check the state ...
...............................................................................!
Fri Mar 11 15:28:48 CST 2016
The CN-SH-DR01is fault error....
Please check the server state ...
...............................................................................!
# tail -10 /var/log/keepalived-state.log
Fri Mar 11 14:42:56 CST 2016
The CN-SH-DR02Starting to become Backup server....
Please run the “ipvsadm -Ln”check the state ...
...............................................................................!
Fri Mar 11 15:06:58 CST 2016
The CN-SH-DR02Starting to become master server....
Please run the “ipvsadm -Ln”check the state ...
...............................................................................!
再次访问http://vip 发现页面为backup-dr的页面：
到这里，整个keepalive+nginx双机热备就部署完成了
总结:关于keepalive+nginx双机热备适合很多web前端高可用集群应用，相对于keepalive+lvs案例应用，配置起来更方便，更简单，与它同样的经典应用案例：keepalive+haproxy也是一个不错的双机热备方案，比如在很多反向代理场景，往往需要根据业务应用来选择这两个应用组合！
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