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  • Keepalived案例一：Keepalived双机热备(HA)精讲

    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：



    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》

    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》

    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，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/
    复制代码

    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
    复制代码
    1. make && make install
    复制代码

    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. }
    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. }
    复制代码


    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. }
    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. }
    复制代码

    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
    复制代码

    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 &
    复制代码

    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
    复制代码

    可以测试了

    开了防火墙之后双节点都变成master了，日志如下
    Sep 13 21:21:27 centosb avahi-daemon[2528]: Withdrawing address record for fe80::20c:29ff:fede:99ab on eth1.
    Sep 13 21:21:27 centosb avahi-daemon[2528]: Withdrawing address record for 192.168.27.212 on eth1.
    Sep 13 21:21:27 centosb avahi-daemon[2528]: Withdrawing address record for fe80::20c:29ff:fede:99a1 on eth0.
    Sep 13 21:21:27 centosb avahi-daemon[2528]: Withdrawing address record for 192.168.17.212 on eth0.
    Sep 13 21:21:27 centosb avahi-daemon[2528]: Host name conflict, retrying with <centosb-48>
    Sep 13 21:21:27 centosb avahi-daemon[2528]: Registering new address record for fe80::20c:29ff:fede:99ab on eth1.
    Sep 13 21:21:27 centosb avahi-daemon[2528]: Registering new address record for 192.168.27.212 on eth1.
    Sep 13 21:21:27 centosb avahi-daemon[2528]: Registering new address record for fe80::20c:29ff:fede:99a1 on eth0.
    Sep 13 21:21:27 centosb avahi-daemon[2528]: Registering new address record for 192.168.17.200 on eth0.
    Sep 13 21:21:27 centosb avahi-daemon[2528]: Registering new address record for 192.168.17.212 on eth0.

    解决方法如下：(一般使用第二种情况）

    第一种情况，如果用的是默认防火墙
    只需要添加：iptables -I RH-Firewall-1-INPUT -d 224.0.0.18 -j ACCEPT

    第二种情况：如果是自己用脚本设置的防火墙，只需要添加西门规则即可
    iptables -A OUTPUT -o eth0 -d 224.0.0.18 -j ACCEPT
    iptables -A OUTPUT -o eth0  -s 224.0.0.18 -j ACCEPT
    iptables -A INPUT -i eth0 -d 224.0.0.18 -j ACCEPT
    iptables -A INPUT -i eth0  -s 224.0.0.18 -j ACCEPT

    修改完后，记得使用/etc/rc.d/init.d/iptables save 保存修改的规则，并会将规则写入/etc/sysconfig/iptables文件中去，否则重启后会失效。

    在/etc/sysconfig/iptables文件中，要将INPUT链和OUTPUT链中的REJECT规则放到最后，否则会影响上面设置的功能。

    最后，使用service iptables restart ，重启iptables使规则生效。

    转自 http://bbs.nanjimao.com/thread-855-1-1.html
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  • 原文地址：https://www.cnblogs.com/enet01/p/11641304.html
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