nginx + keepalive

jgfh · 发表于 2016-9-1 10:17:08

目的: 学习nginx + keepalive结合实现双机热备。

【实现图】

【环境】
master系统配置:
[iyunv@master html]# ifconfig |grep -A 1 eth0
eth0    Link encap:Ethernet  HWaddr 00:0C:29:65:14:0F
      inet addr:192.168.100.10  Bcast:192.168.100.255  Mask:255.255.255.0
[iyunv@master html]# hostname
master
[iyunv@master html]# ifconfig |grep -A 1 eth0
eth0    Link encap:Ethernet  HWaddr 00:0C:29:65:14:0F
      inet addr:192.168.100.10  Bcast:192.168.100.255  Mask:255.255.255.0
[iyunv@master html]# cat /etc/issue | head -1
entOS release 6.4 (Final)

master nginx提前web环境:
[iyunv@master html]# curl 192.168.100.10
<!DOCTYPE html>
<html>
  <h1>192.168.100.10 -- lnmp master -- bbs.test.com</h1>
</html>

slave系统配置:
[iyunv@master ~]# ifconfig |grep -A 2 eth0
eth0    Link encap:Ethernet  HWaddr 00:0C:29:65:14:0F
      inet addr:192.168.100.10  Bcast:192.168.100.255  Mask:255.255.255.0
      inet6 addr: fe80::20c:29ff:fe65:140f/64 Scope:Link
[iyunv@master ~]# hostname
master
[iyunv@master ~]# ifconfig |grep -A 1 eth0
eth0    Link encap:Ethernet  HWaddr 00:0C:29:65:14:0F
      inet addr:192.168.100.10  Bcast:192.168.100.255  Mask:255.255.255.0
[iyunv@master ~]# head -1 /etc/issue
entOS release 6.4 (Final)

slave nginx配置:
[iyunv@slave ~]# curl 192.168.100.13
<!DOCTYPE html>
<html>
<h1>192.168.100.13 -- lnmp slave -- bbs.test.com</h1>
</html>

【安装keepalive】
yum install  keepalived
keepalived-1.2.13-5.el6_6.x86_64

版本号:
[iyunv@master html]# keepalived -v
Keepalived v1.2.13 (03/19,2015)

安装的重要文件:
/etc/keepalived #配置文件目录
/etc/keepalived/keepalived.conf  #配置文件
/etc/rc.d/init.d/keepalived    #启动文件
/etc/sysconfig/keepalived    #keepalived的系统初识化文件
/usr/bin/genhash          #不知道 hash相关的吧
/usr/sbin/keepalived       #keepalived的可执行文件

【配置文件的编写】

去除默认的配置文件
> /etc/keepalived/keepalived.conf
master配置配置文件

! Configuration File for keepalived

#core的定义
global_defs {
notification_email {
      735896273@qq.com
   }
notification_email_from andy@126.com
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id LVS_DEVEL
}

#定义检查脚本
vrrp_script check_http {
      script "/root/check_nginx.sh" # verify the pid existance
      interval 2                   # check every 2 seconds
      weight 2                   # add 2 points of prio if OK 如果检测监本是成功的则优先级加2
}

#配置实例
vrrp_instance VI_1 {
state MASTER #主机为MASTER，备用机为BACKUP
interface eth0                #interface to monitor #HA监测网络接口
virtual_router_id 51          # Assign one ID for this route 主、备机的virtual_router_id必须相同
priority 101                   # 101 on master,100 on backup
nopreempt　　#非抢占(因为默认如果master挂了，backup顶上去，即使master恢复也不抢占！
debug
authentication {
         auth_type PASS       ##VRRP认证方式
         auth_pass mynginx    #密码为mynginx
      }
#VIP地址
virtual_ipaddress {
         192.168.100.12
      }

track_script {
               check_http  (调用nginx进程检测脚本)
      }

}

###############check_http的脚本
[iyunv@master html]# cat /root/check_nginx.sh

1
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#!/bin/bash
A=`ps -C nginx --no-header | wc -l`
if [ $A -eq 0 ];then
/etc/init.d/nginx start
sleep 3
if [ `ps -C nginx --no-header | wc -l` -eq 0 ];then
killall keepalived
fi
fi

当检测到nginx进程不存在的时候，就干掉所有的keepalived，这时候，请求将会由keepalived的backup接管！！
注意: 脚本一定要有执行权限
chmod +x /root/check_nginx.sh

slave配置配置文件：
......

......
state BACKUP #主机为MASTER，备用机为BACKUP

...
priority 100

【启动】
master和slave 的keepalive和nginx都启动
/etc/init.d/keepalived start
/etc/init.d/nignx start

此时可以看到vip在master机器行，因为优先级高
[iyunv@master html]# ip addr show eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 00:0c:29:65:14:0f brd ff:ff:ff:ff:ff:ff
inet 192.168.100.10/24 brd 192.168.100.255 scope global eth0
inet 192.168.100.12/32 scope global eth0
inet6 fe80::20c:29ff:fe65:140f/64 scope link
valid_lft forever preferred_lft forever

【会导致切换的情况】
1 master挂了(机器挂了或者keepalive进程没了)，终归到底keepalive进程没了，此时会vrrp检查对端没包，此时backup接管VIP。
2 check_nginx.sh检查脚本，当检测到nginx进程挂了，且起不来的时候，就把keepalived全部杀掉。
这样当然，就切换到了backup咯。

【疑问】
1 抓包如何抓到vrrp包？
2 keepalive的日志如何弄？
tail -f /var/log/messages
3 非强制好像不起作用。先关掉master的keepalivd再启动master 的keepalived和nginx,master依然会把VIP抢占古来
4 weight像没啥用？
5 检查时间
advert_int 1 #检查间隔，默认1秒6 track_script其实就是用来检测nginx的。

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