keepalived

Keepalived的作⽤是检测服务器的状态，如果有⼀台web服务器宕机，或⼯作出现故障，Keepalived将检测到，并将有故障的服务器从系统中剔除，同时使⽤其他服务器代
替该服务器的⼯作，当服务器⼯作正常后Keepalived⾃动将服务器加⼊到服务器群中，这些⼯作全部⾃动完成，不需要⼈⼯⼲涉，需要⼈⼯做的只是修复故障的服务器。

⼀个监控+⾃愈的软件

Keepalived 安装

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keepalived 安装在分发器上（nginx + keepalived）

http://www.keepalived.org/download.html
wget http://www.keepalived.org/software/keepalived-2.0.8.tar.gz

#cat keepalived_install.sh
#!/bin/bash
pkg=keepalived-2.0.8.tar.gz
tar xf $pkg
yum -y install kernel-devel
ln -s /usr/src/kernels/3.10.0-862.14.4.el7.x86_64/ /usr/src/linux
cd keepalived-2.0.8/
yum install openssl-* -y
./configure --prefix=/usr/local/keepalived
make
make install
mkdir -pv /etc/keepalived
cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/
ln -s /usr/local/keepalived/sbin/keepalived /sbin/

配置Nginx集群

upstream web {
    server 192.168.10.42 max_fails=2 fail_timeout=3;
    server 192.168.10.43 max_fails=2 fail_timeout=3;
}
server {
    listen 80;
    server_name localhost;
    location / {
        proxy_pass http://web;
    }
}

配置keepalived

global_defs {
    router_id NGINX_DEVEL
}
#  定义一个脚本
vrrp_script check_nginx {
    #  脚本路径
    script "/etc/keepalived/nginx_pid.sh"
    #  探针  没两秒运行一次脚本
    interval 2
    #  失败次数
    fall 1
}
#  定义一个实例（使用的是vrrp协议）
vrrp_instance nginx {
    #  定义当前nginx 的状态是  master(主)
    state MASTER
    interface ens33
    mcast_src_ip 192.168.10.40
    virtual_router_id 51
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    track_script {
        #  调用上面定义的脚本
        check_nginx
    }
    virtual_ipaddress {
        192.168.10.213/24
    }
}

关联脚本 nginx_pid.sh

#chmod 755 /etc/keepalived/nginx_pid.sh
#cat /etc/keepalived/nginx_pid.sh
#!/bin/bash
nginx_kp_check () {
    nginxpid=`ps -C nginx --no-header |wc -l`
    if [ $nginxpid -eq 0 ];then
        /usr/local/nginx/sbin/nginx
        sleep 1
        nginxpid=`ps -C nginx --no-header |wc -l`
        if [ $nginxpid -eq 0 ];then
            systemctl stop keepalived
        fi
    fi
}