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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
启动VMware DHCP Service和VMware NAT Service两个服务 在网络适配器开启网络共享，允许其他网络打勾保存，重启虚拟机安装
节点部署
节点 地址 服务 centos7_1 192.168.211.130 Keepalived+Nginx centos7_2 192.168.211.131 Keepalived+Nginx centos7_3 192.168.211.132 Redis服务器 web1（物理机） 192.168.211.128 FastApi+Celery web2（物理机） 192.168.211.129 FastApi+Celeryweb的配置
web1启动python http服务器
vim index.html <html> <body> <h1>Web Svr 1</h1> </body> </html> nohup python -m SimpleHTTPServer 8080 > running.log 2>&1 &web2启动python http服务器
vim index.html <html> <body> <h1>Web Svr 2</h1> </body> </html> 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: $0 {start|stop|status|restart|condrestart|try-restart|reload|force-reload|configtest}” exit 2 esac校验配置文件依次输入下列命令
chkconfig –add nginx chkconfig –level 345 nginx on给这个文件添加执行权限
chmod +x nginx ls functions netconsole network nginx README启动Nginx服务
service nginx start service nginx status service nginx reloadNginx反向代理、负载均衡（centos_1）
修改nginx.conf配置文件，去除注释的代码
cd /usr/local/nginx/conf/ mv nginx.conf nginx.conf.bak egrep -v ^# nginx.conf.bak egrep -v ^#|^[ ]*# nginx.conf.bak egrep -v ^#|^[ ]*#|^$ 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 reloadwebsvr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.bakcentos_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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