centos安装与配置keepalived+nginx高可用

一、安装启动keepalived

1、下载keepalived

在centos系统中，用wget下载最新版本：

mkdir tool

cd tool

wget https://www.keepalived.org/software/keepalived-2.0.19.tar.gz

2、解压安装keepalived

cd tool 

tar -zxvf keepalived-2.0.19.tar.gz -C /usr/local/

yum install -y openssl openssl-devel（需要安装一个软件包）

cd keepalived-2.0.19/ && ./configure --prefix=/usr/local/keepalived

make && make install

3、把keepalived服务配置成开机自启动

将keepalived安装成Linux系统服务，因为没有使用keepalived的默认安装路径（默认路径：/usr/local）,安装完成之后，需要做一些修改工作：
首先创建文件夹，将keepalived配置文件进行复制：
mkdir /etc/keepalived
cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/
然后复制keepalived脚本文件：
#高版本init.d不存在，可以忽略
cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/
cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
ln -s /usr/local/sbin/keepalived /usr/sbin/
ln -s /usr/local/keepalived/sbin/keepalived /sbin/
可以设置开机启动：chkconfig keepalived on，到此我们安装完毕!

4、启动关闭重启

service keepalived start 
service keepalived stop
service keepalived restart 

5、查看安装启动状态，如下启动成功

systemctl status keepalived.service

二、配置keepalived+nginx实现高可用

1、假设keepalived，nginx安装成功，我们开始配置高可用，首先编辑我们时候copy到etc目录的配置文件

vim /etc/keepalived/keepalived.conf

2、在原配置文件keepalived.conf，增加如下画线配置，保存重启keepalived

! Configuration File for keepalived

vrrp_script chk_nginx {
    script "/etc/keepalived/nginx_check.sh" #运行脚本，脚本内容下面有，就是起到一个nginx宕机以后，自动开启服务
    interval 2 #检测时间间隔
    weight -20 #权重
}
# 定义虚拟路由，VI_1 为虚拟路由的标示符，自己定义名称
vrrp_instance VI_1 {
    state MASTER #来决定主从
　　interface ens33 # 绑定虚拟 IP 的网络接口，根据自己的机器填写
    virtual_router_id  # 虚拟路由的 ID 号
    mcast_src_ip 192.168.2.130 #填写本机ip
    priority  # 节点优先级,主要比从节点优先级高
    nopreempt # 优先级高的设置 nopreempt 解决异常恢复后再次抢占的问题
    advert_int  # 组播信息发送间隔，两个节点设置必须一样，默认 1s
    authentication {
        auth_type PASS
        auth_pass
    }
    # 将 track_script 块加入 instance 配置块
    track_script {
        chk_nginx #执行 Nginx 监控的服务
    }

    virtual_ipaddress {
        192.168.2.222 # 虚拟ip,也就是解决写死程序的ip怎么能切换的ip,也可扩展，用途广泛。可配置多个。
    }
}

3、nginx_check.sh文件存在/etc/keepalived目录下/etc/keepalived/nginx_check.sh，内容如下

#!/bin/bash
A=`ps -C nginx 每no-header |wc -l`
if [ $A -eq  ];then
    /usr/local/nginx/sbin/nginx
    sleep
    if [ `ps -C nginx --no-header |wc -l` -eq  ];then
        killall keepalived
    fi
fi

4、如果配置成功，手动 关闭nginx进程，keepalived也会帮我们自动启动 /usr/local/nginx/sbin/nginx，说明配置成功

注意，如果启动keepalived没有报错，但nginx启动失败，大部分原因可能 nginx_check.sh没有权限，也可能是文档格式错误

解决方法：https://blog.csdn.net/chuchanlu6163/article/details/100874598

5、从机也要安装相同的配置的keepalived+nginx

! Configuration File for keepalived

global_defs {
   router_id bhz006
}

vrrp_script chk_nginx {
    script "/etc/keepalived/nginx_check.sh"
    interval 2
    weight -20
}

vrrp_instance VI_1 {
    state BACKUP
    interface eth7
    virtual_router_id
    mcast_src_ip 192.168.1.173
    priority  #优先级配置
    advert_int
    authentication {
        auth_type PASS
        auth_pass 111
    }

    track_script {
        chk_nginx
    }

    virtual_ipaddress {
        192.168.2.220  #主从要一致
    }
}

6、我们可以测试在nginx出现问题的情况下，实现切换，这个时候我们只需要把nginx的配置文件进行修改，让其变得不可用，然后强杀掉nginx进程即可，发现也会实现自动切换服务器节点。

三、如何查看keepalived运行日志？

1、修改vim /etc/sysconfig/keepalived，最后一行为

KEEPALIVED_OPTIONS="-D -d -S 0"

2、修改vi /etc/rsyslog.conf 文件，在最后一行增加

local0.*                      /var/log/keepalived.log

3、重启rsyslog ，如果不知道如何重启rsyslog，首先ps -ef|grep rsyslog，找到该启动进程

然后，/usr/sbin/rsyslogd  -s stop 、/usr/sbin/rsyslogd，有时候用/usr/sbin/rsyslogd restart命令重启失效

4、然后重启keepalived

service keepalived stop

service keepalived start

或者

service keepalived restart

5、然后vim /var/log/keepalived.log就可以看到keepalived日志的的生成