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
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+Celery |
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 {
includemime.types;
default_type application/octet-stream;
sendfile on;
keepalive_timeout 65;
server {
listen80;
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 {
includemime.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 {
listen80;
# 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 {
includemime.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 {
listen80;
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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