1. keepalived简介

1.1 keepalived是什么？

Keepalived 软件起初是专为LVS负载均衡软件设计的，用来管理并监控LVS集群系统中各个服务节点的状态，后来又加入了可以实现高可用的VRRP功能。因此，Keepalived除了能够管理LVS软件外，还可以作为其他服务（例如：Nginx、Haproxy、MySQL等）的高可用解决方案软件。
Keepalived软件主要是通过VRRP协议实现高可用功能的。VRRP是Virtual Router RedundancyProtocol(虚拟路由器冗余协议）的缩写，VRRP出现的目的就是为了解决静态路由单点故障问题的，它能够保证当个别节点宕机时，整个网络可以不间断地运行。
所以，Keepalived 一方面具有配置管理LVS的功能，同时还具有对LVS下面节点进行健康检查的功能，另一方面也可实现系统网络服务的高可用功能。

1.2 keepalived的重要功能

keepalived 有三个重要的功能，分别是：
管理LVS负载均衡软件
实现LVS集群节点的健康检查
作为系统网络服务的高可用性（failover）

1.3 keepalived高可用故障转移的原理

Keepalived 高可用服务之间的故障切换转移，是通过 VRRP (Virtual Router Redundancy Protocol ,虚拟路由器冗余协议）来实现的。
在 Keepalived 服务正常工作时，主 Master 节点会不断地向备节点发送（多播的方式）心跳消息，用以告诉备 Backup 节点自己还活看，当主 Master 节点发生故障时，就无法发送心跳消息，备节点也就因此无法继续检测到来自主 Master 节点的心跳了，于是调用自身的接管程序，接管主 Master 节点的 IP 资源及服务。而当主 Master 节点恢复时，备 Backup 节点又会释放主节点故障时自身接管的IP资源及服务，恢复到原来的备用角色。
那么，什么是VRRP呢？
VRRP ,全称 Virtual Router Redundancy Protocol ,中文名为虚拟路由冗余协议，VRRP的出现就是为了解决静态踣甶的单点故障问题，VRRP是通过一种竞选机制来将路由的任务交给某台VRRP路由器的。

1.4 keepalived原理

1.4.1 keepalived高可用架构图

1.4.2 keepalived工作原理描述

Keepalived高可用是通过 VRRP 进行通信的， VRRP是通过竞选机制来确定主备的，主的优先级高于备，因此，工作时主会优先获得所有的资源，备节点处于等待状态，当主挂了的时候，备节点就会接管主节点的资源，然后顶替主节点对外提供服务。
在 Keepalived 服务之间，只有作为主的服务器会一直发送 VRRP 广播包,告诉备它还活着，此时备不会枪占主，当主不可用时，即备监听不到主发送的广播包时，就会启动相关服务接管资源，保证业务的连续性.接管速度最快可以小于1秒。

2.keepalived实现nginx负载均衡机高可用

2.1 keepalived安装

配置主keepalived

//关闭防火墙与SELINUX
[root@localhost ~]# systemctl stop firewalld
[root@localhost ~]# systemctl disable firewalld
Removed symlink /etc/systemd/system/multi-user.target.wants/firewalld.service.
Removed symlink /etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service.
[root@localhost ~]# setenforce 0
[root@localhost ~]# sed -ri 's/^(SELINUX=).*/1disabled/g' /etc/selinux/config

//配置网络源
[root@localhost yum.repos.d]# wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
[root@localhost yum.repos.d]# sed -i 's#$releasever#7#g' /etc/yum.repos.d/CentOS-Base.repo
[root@localhost yum.repos.d]# wget -O /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-7.repo

//安装keepalived
[root@localhost ~]# yum -y install keepalived

用同样的方法在备服务器上安装keepalived

//关闭防火墙与SELINUX
[root@liping ~]# systemctl stop firewalld
[root@liping ~]# systemctl disable firewalld
Removed symlink /etc/systemd/system/multi-user.target.wants/firewalld.service.
Removed symlink /etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service.
[root@liping ~]# setenforce 0
[root@liping ~]# sed -ri 's/^(SELINUX=).*/1disabled/g' /etc/selinux/config

//配置网络源
[root@liping ~]# wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
[root@liping ~]# sed -i 's#$releasever#7#g' /etc/yum.repos.d/CentOS-Base.repo
[root@liping ~]# wget -O /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-7.repo

//安装keepalived
[root@liping ~]# yum -y install keepalived

2.2 在主备机上分别安装nginx

在master上安装nginx

[root@localhost ~]# yum -y install nginx
[root@localhost ~]# cd /usr/share/nginx/html/
[root@localhost html]# ls
404.html  50x.html  en-US  icons  img  index.html  nginx-logo.png  poweredby.png
[root@localhost html]# mv index.html{,.bak}
[root@localhost html]# echo 'master' > index.html
[root@localhost html]# ls
404.html  50x.html  en-US  icons  img  index.html  index.html.bak  nginx-logo.png  poweredby.png
[root@localhost html]# systemctl start nginx
[root@localhost html]# systemctl enable nginx
Created symlink from /etc/systemd/system/multi-user.target.wants/nginx.service to /usr/lib/systemd/system/nginx.service.
[root@localhost html]# ss -antl
State       Recv-Q Send-Q         Local Address:Port                        Peer Address:Port              
LISTEN      0      128                        *:80                                     *:*                  
LISTEN      0      128                        *:22                                     *:*                  
LISTEN      0      100                127.0.0.1:25                                     *:*                  
LISTEN      0      25                         *:514                                    *:*                  
LISTEN      0      128                       :::80                                    :::*                  
LISTEN      0      128                       :::22                                    :::*                  
LISTEN      0      100                      ::1:25                                    :::*                  
LISTEN      0      25                        :::514                                   :::*

在slave上安装nginx

[root@liping ~]# yum -y install nginx
[root@liping ~]# cd /usr/share/nginx/html/
[root@liping html]# ls
404.html  50x.html  en-US  icons  img  index.html  nginx-logo.png  poweredby.png
[root@liping html]# mv index.html{,.bak}
[root@liping html]# echo 'slave' > index.html
[root@liping html]# ls
404.html  50x.html  en-US  icons  img  index.html  index.html.bak  nginx-logo.png  poweredby.png
[root@liping html]# systemctl start nginx
[root@liping html]# systemctl enable nginx
Created symlink from /etc/systemd/system/multi-user.target.wants/nginx.service to /usr/lib/systemd/system/nginx.service.
[root@liping html]# ss -antl
State       Recv-Q Send-Q         Local Address:Port                        Peer Address:Port              
LISTEN      0      128                        *:80                                     *:*                  
LISTEN      0      128                        *:22                                     *:*                  
LISTEN      0      100                127.0.0.1:25                                     *:*                  
LISTEN      0      128                       :::80                                    :::*                  
LISTEN      0      128                       :::22                                    :::*                  
LISTEN      0      100                      ::1:25                                    :::*

在浏览器上访问试试，确保master上的nginx服务能够正常访问

2.3 keepalived配置

2.3.1 配置主keepalived

[root@localhost html]# cd /etc/keepalived
[root@localhost keepalived]# mv keepalived.conf{,-bak}
[root@localhost keepalived]# ls
keepalived.conf-bak
[root@localhost keepalived]# vim keepalived.conf
global_defs {
    router_id node1
}
vrrp_instance VI_1 {
    state MASTER
    interface ens33
    virtual_router_id 51
    priority 150
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 123456
    }   
    virtual_ipaddress {
        192.168.136.250 dev ens33
    }   
}   
virtual_server 192.168.136.250 80 {
    delay_loop 3
    lvs_sched rr
    lvs_method DR
    protocol TCP
    real_server 192.168.136.153 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
            nb_get_retry 3
  delay_before_retry 3
        }
    }
    real_server 192.168.136.152 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }
}
[root@localhost keepalived]# systemctl start keepalived
[root@localhost keepalived]# systemctl enable keepalived

2.3.2 配置备keepalived

[root@liping html]# cd /etc/keepalived/
[root@liping keepalived]# ls
keepalived.conf
[root@liping keepalived]# mv keepalived.conf{,-bak}
[root@liping keepalived]# ls
keepalived.conf-bak
[root@liping keepalived]# vim keepalived.conf
global_defs {
    router_id node2
}
vrrp_instance VI_1 {
    state BACKUP
    interface ens33
    virtual_router_id 51
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 123456
    }   
    virtual_ipaddress {
        192.168.136.250 dev ens33
    }   
}   
virtual_server 192.168.136.250 80 {
    delay_loop 3
    lvs_sched rr
    lvs_method DR
    protocol TCP
    real_server 192.168.136.153 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
            nb_get_retry 3
  delay_before_retry 3
        }
    }
    real_server 192.168.136.152 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }
}
[root@liping keepalived]# systemctl restart keepalived
[root@liping keepalived]# systemctl enable keepalived

2.3.3 查看VIP在哪里

在MASTER上查看

[root@localhost keepalived]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 00:0c:29:00:52:6e brd ff:ff:ff:ff:ff:ff
    inet 192.168.136.153/24 brd 192.168.136.255 scope global dynamic ens33
       valid_lft 1395sec preferred_lft 1395sec
    inet 192.168.136.250/32 scope global ens33
       valid_lft forever preferred_lft forever
    inet6 fe80::cb81:16ba:de26:872d/64 scope link 
       valid_lft forever preferred_lft forever

在SLAVE上查看

[root@liping keepalived]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 00:0c:29:26:a4:52 brd ff:ff:ff:ff:ff:ff
    inet 192.168.136.152/24 brd 192.168.136.255 scope global dynamic ens33
       valid_lft 1508sec preferred_lft 1508sec
    inet6 fe80::ff7a:d77e:ff2:64bd/64 scope link 
       valid_lft forever preferred_lft forever

用VIP访问

关闭MASTER上的keepalived再用VIP访问

[root@localhost ~]# systemctl stop keepalived
[root@localhost ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 00:0c:29:00:52:6e brd ff:ff:ff:ff:ff:ff
    inet 192.168.136.153/24 brd 192.168.136.255 scope global dynamic ens33
       valid_lft 1103sec preferred_lft 1103sec
    inet6 fe80::cb81:16ba:de26:872d/64 scope link 
       valid_lft forever preferred_lft forever
[root@liping ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 00:0c:29:26:a4:52 brd ff:ff:ff:ff:ff:ff
    inet 192.168.136.152/24 brd 192.168.136.255 scope global dynamic ens33
       valid_lft 1235sec preferred_lft 1235sec
    inet 192.168.136.250/32 scope global ens33
       valid_lft forever preferred_lft forever
    inet6 fe80::ff7a:d77e:ff2:64bd/64 scope link 
       valid_lft forever preferred_lft forever

2.4 让keepalived监控nginx负载均衡机

keepalived通过脚本来监控nginx负载均衡机的状态
在master上编写脚本

[root@localhost ~]# mkdir /scripts
[root@localhost ~]# cd /scripts/
[root@localhost scripts]# vim check_n.sh

#!/bin/bash
nginx_status=$(ps -ef|grep -Ev "grep|$0"|grep 'nginx'|wc -l)
if [ $nginx_status -lt 1 ];then
    systemctl stop keepalived
fi
[root@localhost scripts]# chmod +x check_n.sh 
[root@localhost scripts]# vim notify.sh

#!/bin/bash
VIP=$2
sendmail (){
        subject="${VIP}'s server keepalived state is translate"
        content="`date +'%F %T'`: `hostname`'s state change to master"
        echo $content | mail -s "$subject" 1470044516@qq.com
}
case "$1" in
  master)
        nginx_status=$(ps -ef|grep -Ev "grep|$0"|grep 'nginx'|wc -l)
        if [ $nginx_status -lt 1 ];then
            systemctl start nginx
        fi
        sendmail
  ;;
  backup)
        nginx_status=$(ps -ef|grep -Ev "grep|$0"|grep 'nginx'|wc -l)
        if [ $nginx_status -gt 0 ];then
            systemctl stop nginx
        fi
  ;;
  *)
        echo "Usage:$0 master|backup VIP"
  ;;
esac
[root@localhost scripts]# chmod +x notify.sh

在slave上编写脚本

[root@liping ~]# mkdir /scripts
[root@liping ~]# cd /scripts/
[root@liping scripts]# vim notify.sh

#!/bin/bash
VIP=$2
sendmail (){
        subject="${VIP}'s server keepalived state is translate"
        content="`date +'%F %T'`: `hostname`'s state change to master"
        echo $content | mail -s "$subject" 1470044516@qq.com
}
case "$1" in
  master)
        nginx_status=$(ps -ef|grep -Ev "grep|$0"|grep 'nginx'|wc -l)
        if [ $nginx_status -lt 1 ];then
            systemctl start nginx
        fi
        sendmail
  ;;
  backup)
        nginx_status=$(ps -ef|grep -Ev "grep|$0"|grep 'nginx'|wc -l)
        if [ $nginx_status -gt 0 ];then
            systemctl stop nginx
        fi
  ;;
  *)
        echo "Usage:$0 master|backup VIP"
  ;;
esac
[root@liping scripts]# chmod +x notify.sh

2.5 配置keepalived加入监控脚本的配置

配置主keepalived

[root@localhost ~]# vim /etc/keepalived/keepalived.conf
global_defs {
    router_id node1
}
vrrp_script nginx_check {
    script "/scripts/check_n.sh"
    interval 1
    weight -20
}
vrrp_instance VI_1 {
    state MASTER
    interface ens33
    virtual_router_id 52
    priority 150
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 123456
    }
    virtual_ipaddress {  
        192.168.136.250 dev ens33
    }
}   
track_script {
        nginx_check
    }
    notify_master "/scripts/notify.sh master 192.168.136.250"
    notify_backup "/scripts/notify.sh backup 192.168.136.250"
}   
virtual_server 192.168.136.250 80 {
delay_loop 3
    lvs_sched rr
    lvs_method DR
    protocol TCP
    real_server 192.168.136.153 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }
    real_server 192.168.136.152 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }
}
[root@localhost ~]# systemctl restart keepalived

配置备keepalived

[root@liping ~]# vim /etc/keepalived/keepalived.conf
global_defs {
    router_id node2
}
vrrp_instance VI_1 {
    state BACKUP
    interface ens33
    virtual_router_id 52
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 123456
    }
    virtual_ipaddress {
        192.168.136.250 dev ens33
    }
    notify_master "/scripts/notify.sh master 192.168.136.250"
    notify_backup "/scripts/notify.sh backup 192.168.136.250"
}
virtual_server 192.168.136.250 80 {
    delay_loop 3
    lvs_sched rr
    lvs_method DR
    protocol TCP
    real_server 192.168.136.153 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
global_defs {
    router_id node2
}
vrrp_instance VI_1 {
    state BACKUP
    interface ens33
    virtual_router_id 52
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 123456
    }
    virtual_ipaddress {
        192.168.136.250 dev ens33
    }
    notify_master "/scripts/notify.sh master 192.168.136.250"
    notify_backup "/scripts/notify.sh backup 192.168.136.250"
}
virtual_server 192.168.136.250 80 {
    delay_loop 3
    lvs_sched rr
    lvs_method DR
    protocol TCP
    real_server 192.168.136.153 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
nb_get_retry 3
  delay_before_retry 3
        }
    }
    real_server 192.168.136.152 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }
}

//关闭slave上的nginx，关闭master上的keepalived
[root@liping ~]# systemctl stop nginx
[root@liping ~]# ss -antl
State       Recv-Q Send-Q         Local Address:Port                        Peer Address:Port              
LISTEN      0      128                        *:22                                     *:*                  
LISTEN      0      100                127.0.0.1:25                                     *:*                  
LISTEN      0      128                       :::22                                    :::*                  
LISTEN      0      100                      ::1:25                                    :::*        
[root@localhost ~]# systemctl stop keepalived
//slave上的nginx自动开启
[root@liping ~]# ss -antl
State       Recv-Q Send-Q         Local Address:Port                        Peer Address:Port              
LISTEN      0      128                        *:80                                     *:*                  
LISTEN      0      128                        *:22                                     *:*                  
LISTEN      0      100                127.0.0.1:25                                     *:*                  
LISTEN      0      128                       :::80                                    :::*                  
LISTEN      0      128                       :::22                                    :::*                  
LISTEN      0      100                      ::1:25                                    :::*                  
[root@liping ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 00:0c:29:26:a4:52 brd ff:ff:ff:ff:ff:ff
    inet 192.168.136.152/24 brd 192.168.136.255 scope global dynamic ens33
       valid_lft 1413sec preferred_lft 1413sec
    inet 192.168.136.250/32 scope global ens33
       valid_lft forever preferred_lft forever
    inet6 fe80::ff7a:d77e:ff2:64bd/64 scope link 
       valid_lft forever preferred_lft forever

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