Nginx + keepalived

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Nginx相关概念

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。
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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。
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Nginx的安装

下载nginx

• 官网：http://nginx.org/

上传并解压nginx

命令：tar -zxvf nginx-1.8.1.tar.gz -C /usr/local/src

编译nginx

• 进入到nginx源码目录
  cd /usr/local/src/nginx-1.8.1

• 检查安装环境,并指定将来要安装的路径
  ./configure --prefix=/usr/local/nginx

• 缺包报错

./configure: error: C compiler cc is not found

• 使用YUM安装缺少的包
  yum -y install gcc pcre-devel openssl openssl-devel

• 编译安装
  make && make install

• 安装完后测试是否正常：
  /usr/loca/nginx/sbin/nginx

• 查看端口是否有ngnix进程监听
  netstat -ntlp | grep 80

配置nginx

配置反向代理

• 修改nginx配置文件
  • vim /usr/local/nginx/conf/nginx.conf

server {
    listen       80;
    server_name  demo.nginx.com;    #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://192.168.0.21:8080;   #这里是代理走向的目标服务器：tomcat
    }
}

• 启动配置的tomcat
• 启动nginx
  • ./nginx
• 重启nginx
  • ./nginx -s reload
• 关闭
  • 查询nginx主进程号
    • ps -ef | grep nginx
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  • 从容停止kill -QUIT 主进程号
  • 快速停止kill -TERM 主进程号
  • 强制停止kill -9 nginx所有进程
  • 若nginx.conf配置了pid文件路径，如果没有，则在logs目录下
    • kill -信号类型 '/usr/local/nginx/logs/nginx.pid'

动静分离

#动态资源 index.jsp
location ~ .*\.(jsp|do|action)$ {
    proxy_pass http://tomcat-01.itcast.cn:8080;
}
#静态资源
location ~ .*\.(html|js|css|gif|jpg|jpeg|png)$ {
    expires 3d;
}

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, 已有http, 不是在server里,在server外面
    upstream tomcats { 
        server shizhan02:8080 weight=1;#weight表示权重 数字越大越高
        server shizhan03:8080 weight=1;
        server shizhan04:8080 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
    }
}

利用keepalived实现高可靠

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。

  
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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。

keepalived安装

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

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

将keepalived添加到系统服务中

• 拷贝执行文件
  cp /usr/local/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/keepalived/etc/rc.d/init.d/keepalived
/etc/init.d/keepalived
• 将keepalived文件拷贝到etc下
  cp /usr/local/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/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf
• 添加可执行权限
  chmod +x /etc/init.d/keepalived

以上所有命令一次性执行(绝对路径)：

cp /usr/local/keepalived/sbin/keepalived /usr/sbin/
cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/keepalived
cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/ 
mkdir -p /etc/keepalived
cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf
chmod +x /etc/init.d/keepalived
chkconfig --add keepalived  
chkconfig keepalived on

添加keepalived到开机启动

chkconfig --add keepalived
chkconfig keepalived on

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
        192.168.33.60/24    #如果两个nginx的ip分别是192.168.33.61,,...62，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 {
        192.168.33.60/24
    }
}

• 分别启动两台机器上的keepalived
• 启动命令：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

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

添加切换通知脚本

• vi /usr/local/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/keepalived/sbin/notify.sh

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/keepalived/sbin/notify.sh master"
    notify_backup "/usr/local/keepalived/sbin/notify.sh backup"
    notify_fault "/usr/local/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