keepalived工作原理和配置说明

一、keepalived是什么

keepalived是集群管理中保证集群高可用的一个服务软件，其功能类似于heartbeat，用来防止单点故障。

二、keepalived工作原理

keepalived是以VRRP协议为实现基础的，VRRP全称Virtual Router Redundancy Protocol，即虚拟路由冗余协议。
虚拟路由冗余协议，可以认为是实现路由器高可用的协议，即将N台提供相同功能的路由器组成一个路由器组，这个组里面有一个master和多个backup，master上面有一个对外提供服务的vip（该路由器所在局域网内其他机器的默认路由为该vip），master会发组播，当backup收不到vrrp包时就认为master宕掉了，这时就需要根据VRRP的优先级来选举一个

三、keepalived的安装和配置

安装

1. 解压到指定路径

   tar -zxvf keepalived-1.2.19.tar.gz -C /usr/local/src

2. 切换目录

   cd /usr/local/src/keepalived-1.2.19

3. 配置环境

   ./configure –prefix=/apps/keepalived

4. 编译并且安装

   make && make install

将keepalived添加到系统服务中

• 拷贝执行文件

  cp /apps/keepalived/sbin/keepalived /usr/sbin/

• 将init.d文件拷贝到etc下,加入开机启动项

  cp /apps/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/keepalived

• 将keepalived文件拷贝到etc下

  cp /apps/keepalived/etc/sysconfig/keepalived /etc/sysconfig/

• 创建keepalived文件夹

  mkdir -p /etc/keepalived

• 将keepalived配置文件拷贝到etc下

  cp /apps/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf

• 添加可执行权限

  chmod +x /etc/init.d/keepalived

• 添加keepalived到开机启动

  chkconfig –add keepalived
  chkconfig keepalived on

配置keepalived虚拟IP

修改MASTER配置文件： /etc/keepalived/keepalived.conf

global_defs {}vrrp_instance VI_1 {    state MASTER       interface eth0        virtual_router_id 51       priority 100       advert_int 1      authentication {            auth_type PASS        auth_pass 1111    }    virtual_ipaddress {    #指定虚拟IP, 两个节点设置必须一样     192.168.0.250/24    }}

修改BACKUP配置文件： /etc/keepalived/keepalived.conf

global_defs {}vrrp_instance VI_1 {    state BACKUP    interface eth0    virtual_router_id 51    priority 99    advert_int 1    authentication {        auth_type PASS        auth_pass 1111    }    virtual_ipaddress {        192.168.0.250/24    }}

测试

• 启动MASTER和BACKUP的keepalived服务

service keepalived start

查看ip地址的命令

ip addr

测试结果

杀掉master上的keepalived进程，你会发现，在slave机器上的eth0网卡多了一个ip地址

ps -ef | grep keepalived

* 注意：在MASTER的主机未宕机之前，BACKUP主机网卡地址就出现两个ip地址，可能是BACKUP方主机防火墙未关闭，导致主从之间无法通信*

配置keepalived心跳检查

原理：
Keepalived并不跟nginx耦合，它俩完全不是一家人
但是keepalived提供一个机制：让用户自定义一个shell脚本去检测用户自己的程序，返回状态给keepalived就可以了

MASTER节点

global_defs {}vrrp_script chk_health {    script "[[ `ps -ef | grep nginx | grep -v grep | wc -l` -ge 2 ]] && exit 0 || exit 1"    interval 1    #每隔1秒执行上述的脚本，去检查用户的程序ngnix    weight -2}vrrp_instance VI_1 {    state MASTER    interface eth0    virtual_router_id 1    priority 100    advert_int 2    authentication {        auth_type PASS        auth_pass 1111    }    track_script {        chk_health    }    virtual_ipaddress {        10.0.0.10/24    }    notify_master "/usr/local/keepalived/sbin/notify.sh master"    notify_backup "/usr/local/keepalived/sbin/notify.sh backup"    notify_fault "/usr/local/keepalived/sbin/notify.sh fault"}

添加切换通知脚本

vi /usr/local/keepalived/sbin/notify.sh

#!/bin/bashcase "$1" in    master)        /usr/local/nginx/sbin/nginx        exit 0    ;;backup)        /usr/local/nginx/sbin/nginx -s stop        /usr/local/nginx/sbin/nginx        exit 0    ;;    fault)        /usr/local/nginx/sbin/nginx -s stop        exit 0    ;;    *)        echo 'Usage: notify.sh {master|backup|fault}'        exit 1    ;;esac

添加执行权限

chmod +x /usr/local/keepalived/sbin/notify.sh

global_defs {}vrrp_script chk_health {    script "[[ `ps -ef | grep nginx | grep -v grep | wc -l` -ge 2 ]] && exit 0 || exit 1"    interval 1    weight -2}vrrp_instance VI_1 {    state BACKUP    interface eth0    virtual_router_id 1    priority 99    advert_int 1    authentication {        auth_type PASS        auth_pass 1111    }    track_script {        chk_health    }    virtual_ipaddress {        10.0.0.10/24    }    notify_master "/usr/local/keepalived/sbin/notify.sh master"    notify_backup "/usr/local/keepalived/sbin/notify.sh backup"    notify_fault "/usr/local/keepalived/sbin/notify.sh fault"}