keepalived+nginx实现负载均衡

nginx实现负载均衡，keepalived则主要用来监控nginx的健康状态（keepalived其实不止可以监控nginx其实可以监控redis,memcached等等需要监控的服务），官网：https://www.keepalived.org，nginx的使用方法见我另外一篇文章nginx实现负载均衡，keepalived下载地址https://www.keepalived.org/download.html，下载好了之后，我们先开始安装。

一、使用源码安装

[root@localhost src]# cd /usr/local
[root@localhost src]# mkdir keepalived
[root@localhost src]# wget http://www.keepalived.org/software/keepalived-2.0.20.tar.gz
[root@localhost src]# tar xvf keepalived-2.0.20.tar.gz
[root@localhost src]# cd keepalived-2.0.20
[root@localhost keepalived-2.0.20]# ./configure --prefix=/usr/local/keepalived

#编译后安装
[root@localhost keepalived-2.0.20]# make && make install

# keepalived启动脚本变量引用文件，默认文件路径是/etc/sysconfig/，也可以不做软链接，直接修改启动脚本中文件路径即可（安装目录下）
[root@localhost /]# cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/keepalived

# 将keepalived主程序加入到环境变量（安装目录下）
[root@localhost /]# cp /usr/local/keepalived/sbin/keepalived /usr/sbin/keepalived

# keepalived启动脚本（源码目录下），放到/etc/init.d/目录下就可以使用service命令便捷调用
[root@localhost /]# cp /usr/local/keepalived/keepalived-2.0.20/keepalived/etc/init.d/keepalived /etc/init.d/keepalived

# 将配置文件放到默认路径下
[root@localhost /]# mkdir /etc/keepalived
[root@localhost /]# cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf

二、配置

发现很多第三方软件其实安装了主要就是配置了，比如nginx也是nginx.conf,redis的redis.conf，我实验过如果KeepAlived一个MASTER一个BACKUP，其中MASTER停机后，会出现虚拟ip不会漂移到BACKUP，所以后面我采用的方式是两台都采用backup方式，

这里给出backup01和backup02的配置

BACKUP01配置

! Configuration File for keepalived
vrrp_script chk_nginx {
        script "/etc/keepalived/nginx_check.sh" ## 检测 nginx 状态的脚本路径
        interval 5 ## 检测时间间隔秒
        ##weight -20 ## 如果条件成立，权重-20
}
vrrp_instance VI_1 {
    state BACKUP
    interface eth0
    virtual_router_id 51 ##两台必须一致
    priority 100  ##数字越大优先级越高
    advert_int 1 ##检测是否正常 单位秒
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    track_script {
       chk_nginx ## 执行 Nginx 监控的服务
    }
    nopreempt ##非抢占模式
    unicast_src_ip 100.252.95.101 ##当前服务器ip
    unicast_peer {
        100.252.95.109  ##另外一台备机ip
    }
    virtual_ipaddress {
        100.252.95.88 ##虚拟ip
    }
}

BACKUP02配置

! Configuration File for keepalived
vrrp_script chk_nginx {
        script "/etc/keepalived/nginx_check.sh" ## 检测 nginx 状态的脚本路径
        interval 5 ## 检测时间间隔
        ##weight -20 ## 如果条件成立，权重-20
}
vrrp_instance VI_1 {
    state BACKUP
    interface eth0
    virtual_router_id 51
    priority 99
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    track_script {
       chk_nginx ## 执行 Nginx 监控的服务
    }
    nopreempt
    unicast_src_ip 100.252.95.109
    unicast_peer {
        100.252.95.101
    }
    virtual_ipaddress {
        100.252.95.88
    }
}

这个配置的意思每隔5秒执行一次nginx_check.sh的脚本，即检查nginx是否是健康的，nginx_check.sh的脚本如下

#!/bin/bash
counter=$(ps -C nginx --no-heading|wc -l)
if [ "${counter}" = "0" ]; then
    /usr/local/nginx/sbin/nginx
    sleep 2
    counter=$(ps -C nginx --no-heading|wc -l)
    if [ "${counter}" = "0" ]; then
        /etc/init.d/keepalived stop
    fi
fi

这段代码的意思是入门发现nginx进程不存在了，那么启动异常，启动后发现还不存在，那么keepalived这进程也停止，免得不断的尝试启动Nginx。

三、相关命令

keepalived+nginx实现负载均衡

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