[系统运维]Nginx教程 5.Nginx高可用整合KeepAlived搭建四层负载均衡

nginx自带负载均衡可以实现服务的高可用，但是如果nginx挂了高可用就会有问题，nginx的高可用通过如下来组件实现：

LVS：Linux Virtual Server（Linux虚拟服务器），可以实现虚拟ip，利用服务器集群来实现高可用，与nginx区别在于LVS是OSI四层负载均衡(传输层TCP、UDP)，Nginx用于OSI七层负载均衡（应用层http）

KeepAlived：KeeAlived是在LVS上面做扩展功能，可用于提供监听服务的心跳，自动重启服务。通常与nginx、haproxy搭配使用。支持负载均衡的除了nginx还有haproxy，是专门做负载均衡，相比nginx负载均衡功能更强大

KeepAlived

准备两台Linux服务器：主节点（192.168.126.157）、备节点（192.168.126.161）。分别都安装好KeepAlived并配置，详细步骤如下：

安装步骤

# 下载keepalived安装包
wget http://www.keepalived.org/software/keepalived-2.0.18.tar.gz --no-check-certificate
# 解压
tar -zxvf keepalived-2.0.18.tar.gz && cd keepalived-2.0.18
# 安装相关依赖
# yum -y install libnl libnl-devel
# 编译
./configure --prefix=/usr/local/keepalived
# make一下
make && make install

常见报错
Issued certificate has expired. To connect to www.keepalived.org insecurely,

wget下载https开头的网址域名 时报错，你需要加上 --no-check-certificate (不检查证书)选项

环境搭建

KeepAlived 默认会从 /etc/keepalived/keepalived.conf 路径读取配置文件，所以需要额外cp一份到文件夹中

# 创建目录
mkdir /etc/keepalived
# 拷贝
cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/

拷贝相关文件

# 从安装包目录拷贝
[root@localhost keepalived-2.0.18]# cp keepalived/etc/init.d/keepalived /etc/init.d/
# 从编译好的目录拷贝
cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
cp /usr/local/keepalived/sbin/keepalived /usr/sbin/

配置文件

编写nginx自检测启动脚本

vim /etc/keepalived/nginx_check.sh

脚本内容如下

#!/bin/bash
A=`ps -C nginx –no-header |wc -l`
if [ $A -eq 0 ];then
/usr/local/nginx/sbin/nginx
sleep 2
if [ `ps -C nginx --no-header |wc -l` -eq 0 ];then
	killall keepalived
fi
fi

授权脚本

chmod +x /etc/keepalived/nginx_check.sh

查看网卡信息

[root@localhost keepalived]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    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 group default qlen 1000
    link/ether 00:0c:29:5c:33:98 brd ff:ff:ff:ff:ff:ff
    inet 192.168.126.157/24 brd 192.168.126.255 scope global noprefixroute dynamic ens33
       valid_lft 1351sec preferred_lft 1351sec
    inet6 fe80::4f2e:8438:92e8:f2dd/64 scope link tentative noprefixroute dadfailed 
       valid_lft forever preferred_lft forever
    inet6 fe80::64f9:8f45:f3bf:7da/64 scope link tentative noprefixroute dadfailed 
       valid_lft forever preferred_lft forever
    inet6 fe80::72a5:e5bc:df85:5ef0/64 scope link tentative noprefixroute dadfailed 
       valid_lft forever preferred_lft forever

KeepAlived配置文件内容

1. 主节点配置文件内容

vim /etc/keepalived/keepalived.conf

内容如下

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 #如果条件成立的话，则权重 -20
}
# 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 111 # 虚拟路由的 ID 号， 两个节点设置必须一样
    mcast_src_ip 192.168.126.157 #填写本机ip
    priority 100 # 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 1 # 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 1111
    }
    # 将 track_script 块加入 instance 配置块
    track_script {
        chk_nginx #执行 Nginx 监控的服务
    }

    virtual_ipaddress {
        192.168.126.156 # 虚拟ip,从当前网段找一个没被占用的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。
    }
}

2.备节点配置文件内容

vim /etc/keepalived/keepalived.conf

配置内容如下

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 #如果条件成立的话，则权重 -20
}
# 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 BACKUP #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 111 # 虚拟路由的 ID 号， 与主节点配置一样
    mcast_src_ip 192.168.126.157 #填主节点IP
    priority 90 # 节点优先级,主要比从节点优先级高
    nopreempt
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }

    track_script {
        chk_nginx
    }

    virtual_ipaddress {
        192.168.126.156 # 虚拟ip,与主节点配置一样
    }
}

开启服务

service keepalived start

成功提示

Starting keepalived (via systemctl):                       [  OK  ]

访问虚拟IP：192.168.126.156，测试主备

可停止keepalived用于测试

service keepalived stop

通常云服务器（阿里云）不支持安装KeepAlived虚拟IP，需要额外购买

参考文献：

https://blog.csdn.net/l1028386804/article/details/72801492

https://blog.csdn.net/qq_28533563/article/details/107932712

创作打卡挑战赛

赢取流量/现金/CSDN周边激励大奖