nginx配置

1 Nginx概念

1.1.反向代理

反向代理（Reverse Proxy）方式是指以代理服务器来接受internet上的连接请求，然后将请求转发给内部网络上的服务器，并将从服务器上得到的结果返回给internet上请求连接的客户端，此时代理服务器对外就表现为一个服务器。

1.2.负载均衡

负载均衡，英文名称为Load Balance，是指建立在现有网络结构之上，并提供了一种廉价有效透明的方法扩展网络设备和服务器的带宽、增加吞吐量、加强网络数据处理能力、提高网络的灵活性和可用性。其原理就是数据流量分摊到多个服务器上执行，减轻每台服务器的压力，多台服务器共同完成工作任务，从而提高了数据的吞吐量。

2 Nginx的安装

下载http://nginx.org/
更新yum源yum -y install gcc pcre-devel openssl openssl-devel
上传并解压nginx

cd /usr/local/src
tar -zxvf nginx-1.8.1.tar.gz

编译nginx

cd nginx-1.8.1
./configure --prefix=/usr/local/src/nginx
make && make install

安装完后测试是否正常：

./sbin/nginx
netstat -ntlp | grep 80

3 Nginx配置（配置文件在/conf/nginx.conf）

3.1.配置反向代理

server {
    listen       80;
    server_name  nginx-01.itcast.cn;    #nginx所在服务器的主机名
#反向代理的配置
location / {             #拦截所有请求
        root html;
        proxy_pass http://120.78.70.223:8080;   #这里是代理走向的目标服务器：tomcat
    }
}

重启nginx
kill -HUP `cat /usr/local/src/nginx/logs/nginx.pid `
访问80端口，发现进入8080端口。（相当于将8080端口反向代理给了80端口）

3.2.动静分离

• 动态资源如 index.jsp | do | action | controller

location ~ .*.(jsp|do|action|controller)$ {
    proxy_pass http://120.78.70.223:8080;
}

• 静态资源

location ~ .*.(html|js|css|gif|jpg|jpeg|png)$ {
    expires 3d;
}

3.3.负载均衡

• 在http这个节下面配置一个叫upstream的，后面的名字可以随意取，但是要和location下的proxy_pass http://后的保持一致。

http {
    #是在http里面的, 不是在server里,在server外面
    upstream tomcats {
        server 120.78.70.223:8081 weight=1;
        server 120.78.70.223:8080 weight=1;
    }
#卸载server里
location ~ .*.(jsp|do|action) {
    proxy_pass http://tomcats;        #tomcats是后面的tomcat服务器组的逻辑组号
}
}

4 利用keepalived实现高可靠（HA）（因为如果nginx挂掉了，服务就瘫痪了）

4.1.高可靠概念

• HA(High Available), 高可用性集群，是保证业务连续性的有效解决方案，一般有两个或两个以上的节点，且分为活动节点及备用节点。
  

4.2.高可靠软件keepalived

• keepalive是一款可以实现高可靠的软件，通常部署在2台服务器上，分为一主一备。Keepalived可以对本机上的进程进行检测，一旦Master检测出某个进程出现问题，将自己切换成Backup状态，然后通知另外一个节点切换成Master状态。

4.3.keepalived安装

• 下载keepalived官网:http://keepalived.org
• 解压安装

将keepalived解压到/usr/local/src目录下
cd /usr/local/src/
tar -zxvf  keepalived-1.2.19.tar.gz -C /usr/local/src
cd /usr/local/src/keepalived-1.2.19
开始configure
./configure --prefix=/usr/local/src/keepalived
#编译并安装
make && make install

4.4.将keepalived添加到系统服务中

拷贝执行文件
cp /usr/local/src/keepalived/sbin/keepalived /usr/sbin/
将init.d文件拷贝到etc下,加入开机启动项
cp /usr/local/src/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/keepalived
将keepalived文件拷贝到etc下
cp /usr/local/src/keepalived/etc/sysconfig/keepalived /etc/sysconfig/ 
创建keepalived文件夹
mkdir -p /etc/keepalived
将keepalived配置文件拷贝到etc下
cp /usr/local/src/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf
添加可执行权限
chmod +x /etc/init.d/keepalived
添加keepalived到开机启动
chkconfig --add keepalived	
chkconfig keepalived on

4.5.配置keepalived虚拟IP

修改配置文件： /etc/keepalived/keepalived.conf

• MASTER节点

global_defs {
}
vrrp_instance VI_1 {
    state MASTER   #指定A节点为主节点 备用节点上设置为BACKUP即可
    interface eth0    #绑定虚拟IP的网络接口
    virtual_router_id 51   #VRRP组名，两个节点的设置必须一样，以指明各个节点属于同一VRRP组
    priority 100   #主节点的优先级（1-254之间），备用节点必须比主节点优先级低
    advert_int 1  #组播信息发送间隔，两个节点设置必须一样
    authentication {    #设置验证信息，两个节点必须一致
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {    #指定虚拟IP, 两个节点设置必须一样
        120.78.70.223/24    #如果两个nginx的ip分别是120.78.70.223...224，则此处的虚拟ip跟它俩同一个网段即可
    }
}

• BACKUP节点

global_defs {
}
vrrp_instance VI_1 {
    state BACKUP
    interface eth0
    virtual_router_id 51
    priority 99
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        120.78.70.223/24
    }
}

分别启动两台机器上的keepalived

service keepalived start
测试：
杀掉master上的keepalived进程，你会发现，在slave机器上的eth0网卡多了一个ip地址
查看ip地址的命令： ip addr

4.6.配置keepalived心跳检查

• 原理：
  • Keepalived并不跟nginx耦合，它俩完全不是一家人
  • 但是keepalived提供一个机制：让用户自定义一个shell脚本去检测用户自己的程序，返回状态给keepalived就可以了
• MASTER节点

global_defs {
}

vrrp_script chk_health {
    script "[[ `ps -ef | grep nginx | grep -v grep | wc -l` -ge 2 ]] && exit 0 || exit 1"
    interval 1    #每隔1秒执行上述的脚本，去检查用户的程序ngnix
    weight -2
}

vrrp_instance VI_1 {
    state MASTER
    interface eth0
    virtual_router_id 1
    priority 100
    advert_int 2
    authentication {
        auth_type PASS
        auth_pass 1111
    }

    track_script {
        chk_health
    }

    virtual_ipaddress {
        10.0.0.10/24
    }

    notify_master "/usr/local/src/keepalived/sbin/notify.sh master"
    notify_backup "/usr/local/src/keepalived/sbin/notify.sh backup"
    notify_fault "/usr/local/src/keepalived/sbin/notify.sh fault"
}

• 添加切换通知脚本vim /usr/local/src/keepalived/sbin/notify.sh

#!/bin/bash

case "$1" in
    master)
        /usr/local/nginx/sbin/nginx
        exit 0
    ;;
backup)
        /usr/local/nginx/sbin/nginx -s stop
        /usr/local/nginx/sbin/nginx
        exit 0
    ;;
    fault)
        /usr/local/nginx/sbin/nginx -s stop
        exit 0
    ;;
    *)
        echo 'Usage: notify.sh {master|backup|fault}'
        exit 1
    ;;
esac

• 添加执行权限chmod +x /usr/local/src/keepalived/sbin/notify.sh

• BACKUP节点

global_defs {
}

vrrp_script chk_health {
    script "[[ `ps -ef | grep nginx | grep -v grep | wc -l` -ge 2 ]] && exit 0 || exit 1"
    interval 1
    weight -2
}

vrrp_instance VI_1 {
    state BACKUP
    interface eth0
    virtual_router_id 1
    priority 99
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }

    track_script {
        chk_health
    }

    virtual_ipaddress {
        10.0.0.10/24
    }
	
    notify_master "/usr/local/src/keepalived/sbin/notify.sh master"
    notify_backup "/usr/local/src/keepalived/sbin/notify.sh backup"
    notify_fault "/usr/local/src/keepalived/sbin/notify.sh fault"
}

• 在第二台机器上添加notify.sh脚本
• 分别在两台机器上启动keepalived
  • service keepalived start
  • chkconfig keepalived on