Keepalived双机热备

偏执的太偏执、 2022-08-08 19:31 268阅读 0赞

这里我们仅仅只利用Keepalive做双机热备，也就是保证服务器的高可用性，其他的不用管。可能您会说这样在实际应用中很少会这样用，这您可就错了，Keepalived仅仅做双机热备的情况还是有的，我就碰到过几次这样的案例，下面就我碰到的几个案例做个小结  
  
一，Keepalived双机热备的应用场景  
  
1，网站流量不高，压力不大，但是对服务器的可靠性要求极其高，例如实时在线OA系统，政府部门网站系统，医院实时报医系统，公安局在线报案系统，股市后台网站系统等等，他们的压力不是很大，但是对可靠性要求是非常高的  
  
2，有钱没地方花的，典型的政府企业，公办学校等等  
  
二，Keepalived双机热备的特性以及优缺点  
  
特性：  
1，至少需要两台服务器，其中一台为master始终提供服务，另外一台作为backup始终处于空闲状态，只有在主服务器挂掉的时候他就来帮忙了，这是典型的双击热备  
  
2，能根据需求判断服务是否可用，在不可用的时候要即使切换  
优缺点：  
  
优点：数据同步非常简单，不像负载均衡对数据一致性要求非常高，实现起来相对复杂维护也颇为不便，双机热备用rsync就可以实现了操作和维护非常简单  
  
缺点：服务器有点浪费，始终有一台处于空闲状态  
  
  
三，Keepalived双机热备的配置  
首先画个双机热备拓扑图吧：

![150748peex6wcwcnnegwpt.jpg.thumb.jpg][]

这里我只写最终实现的配置，至于Keepalived的理论知识请参考《 [Keepalived原理与实战精讲][Keepalived] 》  
  
1，本例通过Keepalived来实现两台LNMP(也就是linux+nginx+mysql+php)架构服务器的双机热备  
  
LNMP的配置请参考：《 [Lnmp配置精讲第一版][Lnmp] 》  
  
2，Keepalived配置双机安装配置  
  
1》Keepalived安装  
  
keepalived官方地址： [http://www.keepalived.org/download.html][http_www.keepalived.org_download.html] ，大家可以到这里下载最新版本的keepalived  
  
操作系统：centos 5.5 32bit  
系统安装：最小化安装，也就是去掉所有组件  
环境配置：安装make 和 gcc openssl openssl-devel等等

1.  yum -y install gcc make openssl openssl-devel wget kernel-devel  
    
2.  mkdir -p /usr/local/src/hasoft  
    
3.  cd /usr/local/src/hasoft  
    
4.  wget http://www.keepalived.org/software/keepalived-1.2.2.tar.gz  
    
5.  tar -zxvf keepalived-1.2.2.tar.gz  
    
6.  cd keepalived-1.2.2  
    
7.  ./configure --prefix=/usr/local/keepalived --with-kernel-dir=/usr/src/kernels/2.6.18-238.19.1.el5-i686/

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预编译后出现：

1.  Keepalived configuration  
    
2.  \------------------------  
    
3.  Keepalived version : 1.2.2  
    
4.  Compiler : gcc  
    
5.  Compiler flags : -g -O2 -DETHERTYPE\_IPV6=0x86dd  
    
6.  Extra Lib : -lpopt -lssl -lcrypto  
    
7.  Use IPVS Framework : Yes  
    
8.  IPVS sync daemon support : Yes  
    
9.  IPVS use libnl : No  
    
10. Use VRRP Framework : Yes  
    
11. Use Debug flags : No

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1.  make && make install

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这里注意哦，我上面是指通用的安装方法，如果你没有用到LVS可以把lvs去掉即  
./configure --prefix=/usr/local/keepalived --with-kernel-dir=/usr/src/kernels/2.6.18-238.19.1.el5-i686/ --disable-lvs-syncd --disable-lvs  
  
但这个没有影响，就按照我的来配置吧，不过如果你要是集成了LVS，那么就不可加这两个参数了哦  
  
整理管理文件：  
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/  
  
  
建立配置文件目录(注意：keepalived的配置文件默认在/etc/keepalived/目录)  
mkdir -p /etc/etc/keepalived/  
  
两台服务器(两个节点)都这样安装即可  
  
2》配置  
  
节点A配置如下：  
vi /etc/keepalived/keepalived.conf

1.  global\_defs  
    
2.  \{  
    
3.  notification\_email  
    
4.  \{  
    
5.  admin@example.com  
    
6.  admin@ywlm.net  
    
7.  \}  
    
8.  notification\_email\_from admin@example.com  
    
9.  smtp\_server 127.0.0.1  
    
10. stmp\_connect\_timeout 30  
    
11. router\_id lnmp\_node1  
    
12. \}  
    
13.   
    
14. vrrp\_instance lnmp \{  
    
15. state MASTER  
    
16. interface eth0  
    
17. virtual\_router\_id 100  
    
18. priority 200  
    
19. advert\_int 5  
    
20. track\_interface \{  
    
21. eth0  
    
22. eth1  
    
23. \}  
    
24. authentication \{  
    
25. auth\_type PASS  
    
26. auth\_pass 123456  
    
27. \}  
    
28. virtual\_ipaddress \{  
    
29. 192.168.17.200  
    
30. \}  
    
31. \}

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节点B配置如下：  
vi /etc/keepalived/keepalived.conf

1.  global\_defs  
    
2.  \{  
    
3.  notification\_email  
    
4.  \{  
    
5.  admin@example.com  
    
6.  admin@ywlm.net  
    
7.  \}  
    
8.  notification\_email\_from admin@example.com  
    
9.  smtp\_server 127.0.0.1  
    
10. stmp\_connect\_timeout 30  
    
11. router\_id lnmp\_node1  
    
12. \}  
    
13.   
    
14. vrrp\_instance lnmp \{  
    
15. state MASTER  
    
16. interface eth0  
    
17. virtual\_router\_id 100  
    
18. priority 150  
    
19. advert\_int 5  
    
20. track\_interface \{  
    
21. eth0  
    
22. eth1  
    
23. \}  
    
24. authentication \{  
    
25. auth\_type PASS  
    
26. auth\_pass 123456  
    
27. \}  
    
28. virtual\_ipaddress \{  
    
29. 192.168.17.200  
    
30. \}  
    
31. \}

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四，启动调试  
在节点A上启动  
/usr/local/keepalived/sbin/keepalived  
  
启动日志：  
Sep 8 18:26:02 centosa Keepalived\_vrrp: Registering Kernel netlink reflector  
Sep 8 18:26:02 centosa Keepalived\_vrrp: Registering Kernel netlink command channel  
Sep 8 18:26:02 centosa Keepalived\_vrrp: Registering gratutious ARP shared channel  
Sep 8 18:26:02 centosa Keepalived\_vrrp:  Opening file '/etc/keepalived/keepalived.conf'.  
Sep 8 18:26:02 centosa Keepalived\_vrrp: Configuration is using : 36076 Bytes  
Sep 8 18:26:02 centosa Keepalived\_vrrp: Using LinkWatch kernel netlink reflector...  
Sep 8 18:26:02 centosa Keepalived: Starting VRRP child process, pid=5606  
Sep 8 18:26:07 centosa Keepalived\_vrrp:  VRRP\_Instance(lnmp) Transition to MASTER STATE  
Sep 8 18:26:12 centosa Keepalived\_vrrp:  VRRP\_Instance(lnmp) Entering MASTER STATE  
Sep 8 18:26:12 centosa avahi-daemon\[2528\]: Registering new address record for 192.168.17.200 on eth0.  
  
  
在节点B上启动  
/usr/local/keepalived/sbin/keepalived  
  
开机自动启动  
echo /usr/local/keepalived/sbin/keepalived >> /etc/rc.local  
  
启动日志：  
Sep 8 18:30:02 centosb Keepalived: Starting Keepalived v1.2.2 (09/08,2011)  
Sep 8 18:30:02 centosb Keepalived: Starting Healthcheck child process, pid=5837  
Sep 8 18:30:02 centosb Keepalived\_vrrp: Registering Kernel netlink reflector  
Sep 8 18:30:02 centosb Keepalived\_vrrp: Registering Kernel netlink command channel  
Sep 8 18:30:02 centosb Keepalived\_vrrp: Registering gratutious ARP shared channel  
Sep 8 18:30:02 centosb Keepalived: Starting VRRP child process, pid=5839  
Sep 8 18:30:02 centosb kernel: IPVS: Registered protocols (TCP, UDP, AH, ESP)  
Sep 8 18:30:02 centosb kernel: IPVS: Connection hash table configured (size=4096, memory=32Kbytes)  
Sep 8 18:30:02 centosb kernel: IPVS: ipvs loaded.  
Sep 8 18:30:02 centosb Keepalived\_healthcheckers: Registering Kernel netlink reflector  
Sep 8 18:30:02 centosb Keepalived\_healthcheckers: Registering Kernel netlink command channel  
Sep 8 18:30:02 centosb Keepalived\_healthcheckers: Opening file '/etc/keepalived/keepalived.conf'.  
Sep 8 18:30:02 centosb Keepalived\_vrrp:  Opening file '/etc/keepalived/keepalived.conf'.  
Sep 8 18:30:02 centosb Keepalived\_vrrp: Configuration is using : 36252 Bytes  
Sep 8 18:30:02 centosb Keepalived\_vrrp: Using LinkWatch kernel netlink reflector...  
Sep 8 18:30:02 centosb Keepalived\_healthcheckers: Configuration is using : 6271 Bytes  
Sep 8 18:30:02 centosb Keepalived\_healthcheckers: Using LinkWatch kernel netlink reflector...  
Sep 8 18:30:02 centosb Keepalived\_vrrp:  VRRP\_Instance(lnmp) Entering BACKUP STATE  
  
从日志可以看出，启动都没有问题，并且安装我给的优先级完成了竞选，各自成就了各自的状态  
  
关闭节点A的网卡测试切换是否正常  
ifdown eth0  
  
观察节点B的日志：  
Sep 8 18:32:55 centosb Keepalived\_vrrp: VRRP\_Instance(lnmp) Transition to MASTER STATE  
Sep 8 18:33:00 centosb Keepalived\_vrrp: VRRP\_Instance(lnmp) Entering MASTER STATE  
Sep 8 18:33:00 centosb avahi-daemon\[2531\]:  Registering  new address record for 192.168.17.200 on eth0.  
  
  
启动节点A的网卡测试切换是否正常  
ifup eth0  
观察节点B的日志：  
Sep 8 18:33:31 centosb Keepalived\_vrrp: VRRP\_Instance(lnmp) Received higher prio advert  
Sep 8 18:33:31 centosb Keepalived\_vrrp: VRRP\_Instance(lnmp) Entering BACKUP STATE  
Sep 8 18:33:31 centosb avahi-daemon\[2531\]:  Withdrawing  address record for 192.168.17.200 on eth0.  
  
Received higher prio advert：表示接收到更高优先级的公告(advert公告的意思)  
Withdrawing： 撤回的意思，可以看出切换过程一目了然  
  
  
OK，到这里我们的安装部分完成，下面我们来看看如何监控服务吧，我们这里仅仅是监控了网络故障和keepalived本身进程，在网络或者keepalived进程出现问题的时候会切换，但是我的节点A里面还有很多服务呢，例如nginx，PHP，mysql进程出问题或高负载的时候相应过慢怎么办，怎么切换的呢，这时就要用到脚本了，下面我们来看看keepalived是如何控制脚本来实现对服务器的监控和切换的  
  
写个脚本来实时监控三个服务，若有一个出现问题遍切换mkdir /root/shell/  
cd /root/shell  
vi keepcheck.sh

1.  \#!/bin/bash  
    
2.  while :  
    
3.  do  
    
4.  mysqlcheck=\`/usr/local/lnmp/mysql/bin/mysqladmin -uroot ping 2>&1\`  
    
5.  mysqlcode=\`echo $?\`  
    
6.  phpcheck=\`ps -C php-fpm --no-header | wc -l\`  
    
7.  nginxcheck=\`ps -C nginx --no-header | wc -l\`  
    
8.  keepalivedcheck=\`ps -C keepalived --no-header | wc -l\`  
    
9.  if \[ $nginxcheck -eq 0 \]|| \[ $phpcheck -eq 0 \]||\[ $mysqlcode -ne 0 \];then  
    
10. if \[ $keepalivedcheck -ne 0 \];then  
    
11. killall -TERM keepalived  
    
12. else  
    
13. echo "keepalived is stoped"  
    
14. fi  
    
15. else  
    
16. if \[ $keepalivedcheck -eq 0 \];then  
    
17. /etc/init.d/keepalived start  
    
18. else  
    
19. echo "keepalived is running"  
    
20. fi  
    
21. fi  
    
22. sleep 5  
    
23. done  
    
24.

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注意，用 /etc/init.d/keepalived start如果起不来，可以用/usr/local/keepalived/sbin/keepalived二进制文件直接执行启动即可  
启动脚本：

1.  chmod +x /root/shell/keepcheck.sh  
    
2.  nohup sh /root/shell/keepcheck.sh &

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节点B也用这个脚本  
  
写入/etc/rc.local开机自动启动

1.  echo "nohup sh /root/shell/keepcheck.sh &" >> /etc/rc.loal

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可以测试了  
  
本文就写完了，这个可以用于生产环境，本人环境就这样配置的，但不同业务有不同环境，一定要按需调整，不要盲目盲从！

[150748peex6wcwcnnegwpt.jpg.thumb.jpg]: http://bbs.nanjimao.com/data/attachment/forum/201109/09/150748peex6wcwcnnegwpt.jpg.thumb.jpg
[Keepalived]: http://bbs.ywlm.net/thread-845-1-1.html
[Lnmp]: http://bbs.ywlm.net/thread-2-1-1.html
[http_www.keepalived.org_download.html]: http://www.keepalived.org/download.html