前言

用nginx做负载均衡，作为架构的最前端或中间层，随着日益增长的访问量，需要给负载均衡做高可用架构，利用keepalived解决单点风险，一旦 nginx宕机能快速切换到备份服务器。

Vmware网络配置可能遇到的问题解决方法

安装

节点部署

web的配置

web1启动python http服务器

vim index.html



Web Svr 1



nohup python -m SimpleHTTPServer 8080 > running.log 2>&1 &

web2启动python http服务器

vim index.html



Web Svr 2



nohup python -m SimpleHTTPServer 8080 > running.log 2>&1 &

关闭防火墙

firewall-cmd --state
systemctl stop firewalld.service
systemctl disable firewalld.service

现在浏览器访问就正常了，页面显示Web Svr 1 和 2

centos1和2安装Nginx

首先配置阿里云的源

mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
wget -O /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-7.repo
sed -i -e "/mirrors.cloud.aliyuncs.com/d" -e "/mirrors.aliyuncs.com/d" /etc/yum.repos.d/CentOS-Base.repo

安装依赖包

yum -y install gcc
yum install -y pcre pcre-devel
yum install -y zlib zlib-devel
yum install -y openssl openssl-devel

下载nginx，并解压

wget http://nginx.org/download/nginx-1.8.0.tar.gz
tar -zxvf nginx-1.8.0.tar.gz

安装nginx

cd nginx-1.8.0
./configure --user=nobody --group=nobody --prefix=/usr/local/nginx --with-http_stub_status_module --with-http_gzip_static_module --with-http_realip_module --with-http_sub_module --with-http_ssl_module
make
make install
cd /usr/local/nginx/sbin/
# 检查配置文件
./nginx -t
# 启动nginx
./nginx

开放nginx访问

firewall-cmd --zone=public --add-port=80/tcp --permanent
systemctl restart firewalld.service

此时访问130和131都可以看到nginx的首页。

创建nginx启动文件

需要在init.d文件夹中创建nginx启动文件。 这样每次服务器重新启动init进程都会自动启动Nginx。

cd /etc/init.d/
vim nginx

#!/bin/sh
#
# nginx - this script starts and stops the nginx daemin
#
# chkconfig:   - 85 15
# description:  Nginx is an HTTP(S) server, HTTP(S) reverse 
#               proxy and IMAP/POP3 proxy server
# processname: nginx
# config:      /etc/nginx/nginx.conf
# pidfile:     /var/run/nginx.pid
# user:        nginx

# Source function library.
. /etc/rc.d/init.d/functions

# Source networking configuration.
. /etc/sysconfig/network

# Check that networking is up.
[ "$NETWORKING" = "no" ] && exit 0

nginx="/usr/local/nginx/sbin/nginx"
prog=$(basename $nginx)

NGINX_CONF_FILE="/usr/local/nginx/conf/nginx.conf"

lockfile=/var/run/nginx.lock

start() {
    [ -x $nginx ] || exit 5
    [ -f $NGINX_CONF_FILE ] || exit 6
    echo -n $"Starting $prog: "
    daemon $nginx -c $NGINX_CONF_FILE
    retval=$?
    echo
    [ $retval -eq 0 ] && touch $lockfile
    return $retval
}

stop() {
    echo -n $"Stopping $prog: "
    killproc $prog -QUIT
    retval=$?
    echo
    [ $retval -eq 0 ] && rm -f $lockfile
    return $retval
}

restart() {
    configtest || return $?
    stop
    start
}

reload() {
    configtest || return $?
    echo -n $"Reloading $prog: "
    killproc $nginx -HUP
    RETVAL=$?
    echo
}

force_reload() {
    restart
}

configtest() {
  $nginx -t -c $NGINX_CONF_FILE
}

rh_status() {
    status $prog
}

rh_status_q() {
    rh_status >/dev/null 2>&1
}

case "$1" in
    start)
        rh_status_q && exit 0
        $1
        ;;
    stop)
        rh_status_q || exit 0
        $1
        ;;
    restart|configtest)
        $1
        ;;
    reload)
        rh_status_q || exit 7
        $1
        ;;
    force-reload)
        force_reload
        ;;
    status)
        rh_status
        ;;
    condrestart|try-restart)
        rh_status_q || exit 0
            ;;
    *)
        echo $"Usage: $0 {start|stop|status|restart|condrestart|try-restart|reload|force-reload|configtest}"
        exit 2
esac

校验配置文件依次输入下列命令

chkconfig --add nginx
chkconfig --level 345 nginx on

给这个文件添加执行权限

chmod +x nginx 
ls

functions  netconsole  network  nginx  README

启动Nginx服务

service nginx start
service nginx status
service nginx reload

Nginx反向代理、负载均衡（centos_1）

修改nginx.conf配置文件，去除注释的代码

cd /usr/local/nginx/conf/
mv nginx.conf nginx.conf.bak
egrep -v "^#" nginx.conf.bak
egrep -v "^#|^[ ]*#" nginx.conf.bak
egrep -v "^#|^[ ]*#|^$" nginx.conf.bak 
egrep -v "^#|^[ ]*#|^$" nginx.conf.bak >> nginx.conf
cat nginx.conf

输出如下

worker_processes  1;
events {
    worker_connections  1024;
}
http {
    include       mime.types;
    default_type  application/octet-stream;
    sendfile        on;
    keepalive_timeout  65;
    server {
        listen       80;
        server_name  localhost;
        location / {
            root   html;
            index  index.html index.htm;
        }
        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   html;
        }
    }
}

重新加载nginx配置

# 测试配置文件是否正常
../sbin/nginx -t
# 重新加载nginx配置
../sbin/nginx -s reload

配置nginx反向代理、负载均衡

worker_processes  1;
events {
    worker_connections  1024;
}
http {
    include       mime.types;
    default_type  application/octet-stream;
    sendfile        on;
    keepalive_timeout  65;
    
    # websvr 服务器集群（也可以叫负载均衡池）	
    upstream websvr {
        server 192.168.211.128:8001  weight=1;
        server 192.168.211.129:8001  weight=2;
    }
	
    server {
        listen       80;
        # 用来指定ip地址或者域名，多个配置之间用空格分隔
        server_name  192.168.211.130;
        location / {
            # 将所有请求交给websvr集群去处理
            proxy_pass http://websvr;
        }
        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   html;
        }
    }
}

现在重启nginx

sbin/nginx -s reload

websvr名称可自定义，可以指明这些服务器的含义。也就是只需要添加upstream websvr和proxy_pass就可以实现负载均衡。

现在访问130，页面上就会出现Web Svr 1和Web Svr 2切换，会根据权重选择服务器，weight值越大，权重越高，也就是重复刷新该页面，平均Web Svr 2出现2次，Web Svr 1出现1次。

到目前为止，仍然不能实现高可用，虽然web服务可以这样做，单点故障可以通过这种方式处理，但是如果nginx服务故障了，整个系统基本就无法访问了，那么就需要使用多台Nginx来保障。

多个Nginx协同工作，Nginx高可用【双机主从模式】

在131服务器（centos_2）上新增一台nginx服务，和之前的配置一样，只需要修改 nginx.conf 即可

worker_processes  1;
events {
    worker_connections  1024;
}
http {
    include       mime.types;
    default_type  application/octet-stream;
    sendfile        on;
    keepalive_timeout  65;

        upstream websvr {
        server 192.168.211.128:8001  weight=1;
        server 192.168.211.129:8001  weight=2;
    }

    server {
        listen       80;
        server_name  192.168.211.131;
        location / {
            proxy_pass http://websvr;
        }
        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   html;
        }
    }
}

# 重新加载nginx
sbin/nginx -s reload

现在访问 http://192.168.211.130/ 也可以得到和 http://192.168.211.131/ 类似的结果。

这两台Nginx服务器的IP是不同的，那怎么做才能将这两台nginx服务器一起工作呢？这就需要用到keepalived了。

安装软件，两台centos同时安装

yum install keepalived pcre-devel  -y

配置keepalived

两台均备份

cp /etc/keepalived/keepalived.conf keepalived.conf.bak

centos_1配置Keepalived-MASTER

[root@localhost keepalived]# cat keepalived.conf
! Configuration File for keepalived

global_defs {
    script_user root
	enable_script_security
}

vrrp_script chk_nginx {
    # 指定监控脚本，检测nginx服务是否正常运行
    script "/etc/keepalived/chk_nginx.sh"
    # 指定监控时间，每10s执行一次
    interval 10
    # 脚本结果导致的优先级变更，检测失败（脚本返回非0）则优先级 -5
    # weight -5
    # # 检测连续2次失败才算确定是真失败。会用weight减少优先级（1-255之间）
    # fall 2
    # 检测1次成功就算成功。但不修改优先级
    # rise 1
}

vrrp_instance VI_1 {
	# 指定keepalived的角色，主机设置为MASTER，备用机设置为BACKUP
    state BACKUP
	# 指定HA监测网络的接口。centos7使用 ip addr 获取
    interface ens33
	# 主备的virtual_router_id必须一样，可以设置为IP后一组：must be between 1 & 255
    virtual_router_id 51
	# 优先级值，在同一个vrrp_instance下， MASTRE 一定要高于 BAUCKUP，MASTER恢复后，BACKUP自动交接
    priority 90
	# VRRP 广播周期秒数，如果没检测到该广播，就被认为服务挂了，将切换主备
    advert_int 1
	# 设置验证类型和密码。主从必须一样
    authentication {
		# 设置vrrp验证类型，主要有PASS和AH两种
        auth_type PASS
		# 加密的密码，两台服务器一定要一样，才能正常通信
        auth_pass 1111
    }
	track_script {
        # 执行监控的服务，引用VRRP脚本，即在 vrrp_script 部分指定的名字。定期运行它们来改变优先级
        chk_nginx
    }
    virtual_ipaddress {
		# VRRP HA 虚拟地址 如果有多个VIP，继续换行填写
        192.168.211.140
    }
}

把配置文件发送到131节点

scp /etc/keepalived/keppalived.conf 192.168.211.131:/etc/keepalived/keepalived.conf

对于131节点只需要修改

state BACKUP
priority 90

主keepalived配置监控脚本chk_nginx.sh

创建一个脚本，用于在keepalived中执行

vi /etc/keepalived/chk_nginx.sh

#!/bin/bash
# 查看是否有 nginx进程 把值赋给变量counter
counter=`ps -C nginx --no-header |wc -l`
# 如果没有进程值得为 0
if [ $counter -eq 0 ];then
    # 尝试启动nginx
    echo "Keepalived Info: Try to start nginx" >> /var/log/messages
    /etc/nginx/sbin/nginx
    sleep 3
    if [ `ps -C nginx --no-header |wc -l` -eq 0 ];then
        # 输出日至道系统消息
        echo "Keepalived Info: Unable to start nginx" >> /var/log/messages
        # 如果还没没启动，则结束 keepalived 进程
        # killall keepalived
        # 或者停止
        /etc/init.d/keepalived stop
        exit 1
    else
        echo "Keepalived Info: Nginx service has been restored" >> /var/log/messages
        exit 0
    fi
else
    # 状态正常
    echo "Keepalived Info: Nginx detection is normal" >> /var/log/messages;
    exit 0
fi

接下来授予执行权限，并测试

chmod +x chk_nginx.sh
./chk_nginx.sh

两边重启keepalived

systemctl restart keepalived
systemctl status keepalived

此时访问.140也是可以正常显示的，也就是绑定的IP成功了。执行前可以通过下面命令实时查看 messages 中的输出日志

tail -f /var/log/messages 

# 如果nginx关闭
Keepalived Info: Try to start nginx
Keepalived Info: Nginx service has been restored
# nginx正常打开
Keepalived Info: Nginx detection is normal

当nginx检测正常，就会返回0；检测没有了，返回1，但是keepalived似乎不是检测这个返回值来实现转移，而是检测keepalived服务是否存在，来释放本地VIP后，最终转移虚拟IP，到另一台服务器。

参考文章

https://www.jianshu.com/p/7e8e61d34960
https://www.cnblogs.com/zhangxingeng/p/10721083.html

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