What is nginx in linux

In Linux, nginx is a high-performance HTTP and reverse proxy web server. It is a high-performance http server, reverse proxy server and email (IMAP/POP3) proxy server.

#The operating environment of this tutorial: linux5.9.8 system, Dell G3 computer.

What is nginx

Apache static resource server

nginx is a reverse proxy static resource server.

nginx is a high-performance http server and reverse proxy server developed using c language. Nginx is a high-performance http server/reverse proxy server and email (IMAP/POP3) proxy server. Developed by Russian programmer Igor Sysoev, the official test of nginx can support 50,000 concurrent connections, and consumes very low CPU, memory and other resources, and runs very stably.

Forward proxy:

Reverse proxy:

Reverse proxy is generally used on the server side to distribute requests and achieve load balanced.

Application scenarios of Nginx

1. http server. Nginx is an http service that can provide http services independently. Can be used as a static web server.

2. Virtual host. Multiple websites can be virtualized on one server. For example, a virtual host used by a personal website.

Port-based, different terminals

Based on domain name, different domain names

3. Reverse proxy, load balancing. When the number of visits to the website reaches a certain level and a single server cannot satisfy user requests, multiple server clusters are needed and nginx can be used as a reverse proxy. And multiple servers can share the load evenly, and there will be no downtime due to a high load on a certain server and a certain server will not be idle.

nginx click version to install and start the service

1. Install the plug-ins required for the nginx service

yum install -y yum-utils

2. Install nginx

There is no nginx in the official yum source, but we can configure the yam source of nginx on this machine to implement the yum installation of nginx.

Then create a nginx.repo file:

[nginx]
 name=nginx repo
 baseurl=http://nginx.org/packages/centos/7/$basearch/
 gpgcheck=0
 enabled=1

Installed:

Management commands for nginx service ：

systemctl start/stop/restart/status nginx

3. The selinux service of the linux operating system needs to be closed

Selinux is a security service suite for Linux

Modify the vi /etc/selinux/config file and modify the following content:

After modification, Linux must be restarted.
nginx configuration file:

The configuration file we will often modify in the future is /etc/nginx/conf.d/default.conf:

Use nginx for load balancing

After downloading the compressed package, transfer it to the linux opt folder through xftp and decompress it

The first step is to start two tomcats on our linux server

先配置jdk环境变量：


然后 保存退出 ，在命令行执行 source 命令 编译环境变量文件，让环境变量立刻生效：

tomcat 启动：

第二步，准备两个tomcat 一个端口号弄成8000 另外一个9000



第三步，修改nginx的配置文件
没有安装vim，使用vi命令


然后重启nginx服务：

nginx支持的负载均衡的策略

轮询策略

默认nginx支持的策略，来了请求之后 排队把请求一个一个的分发出去。

权重策略

IP_HASH方式

根据 客户端ip地址 固定分配到一台服务器上，以后这个ip来的所有请求 都会只到这一个服务器上。

使用keepalived 完成 nginx 高可用配置

上面我们实现的集群方式 可以解决tomcat 服务器单点故障的问题，但是解决不了 nginx服务器单点故障的问题。

解决nginx 单点故障问题，市场上通用的解决方案就是使用keepalived 这种插件。

先安装keepalived服务：


下面修改keepalived的配置文件: vim /etc/keepalived/keepalived.conf文件：

global_defs { 
	notification_email { 
		#keepalived如果检测到nginx服务不能用会往这个邮件发信心 
		test@163.com 
	}
	#配置邮件服务器的信息 
	notification_email_from keepalived@localhost 
	smtp_server 127.0.0.1 
	smtp_connect_timeout 30 
	router_id LVS_MASTER
}
#声明一个脚本 
vrrp_script chk_http_port { 
	#检测本机nginx的服务是否能用的脚本 这个脚本等下要自己编写 
	script "/usr/local/src/check_nginx_pid.sh" 
	#每隔多长时间自动调用上述脚本 
	interval 2 
	#权重 
	weight 2 
}
vrrp_instance VI_1 { 
	#state MASTER 
	#配置当前的nginx服务器是主机还是备机 
	state BACKUP 
	#配置当前nginx服务是是否非抢占模式 
	#nopreempt 
	#配置心跳网卡的名称 
	interface ens33 
	#所有的keepalived的服务器的虚拟化路由都要一致 
	virtual_router_id 50 
	#nginx服务器的初始化权重 
	priority 100
	#心跳连接发送的间隔 
	advert_int 1 
	#认证方式和认证密码 要保证所有keepalive的服务器的验证方式和密码都一样 
	authentication { 
		auth_type PASS 
		auth_pass 1111 
	}
	#启用上述脚本 
	track_script {
		 chk_http_port 
	}
	virtual_ipaddress { 
		#配置了keeplived服务器之后再访问tomcat集群虚拟的ip地址时多少
		192.168.17.222 
		#虚拟ip 
	} 
}

下一步，写/usr/local/src/check_nginx_pid.sh这个脚本：

#! /bin/bash 
A=`ps -C nginx --no-header |wc -l` 
if [ $A -eq 0 ];then 
systemctl start nginx 
if [ `ps -C nginx --no-header |wc -l` -eq 0 ];then 
killall keepalived 
fi
fi

创建好这个脚本之后 不要忘记修改文件的权限：

下面启动keepalived服务：

systemctl start keepalived

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