1. Nginx相关概念

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

2.1.  下载nginx

官网：

2.2.  上传并解压nginx

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

2.3.  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

3. 配置Nginx

3.1 配置反向代理

1.修改nginx配置文件

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://192.168.0.21:8080;   #这里是代理走向的目标服务器：tomcat    }}

2. 启动tomcat-01上的tomcat

3. 启动nginx-01上的nginx

./nginx

重启:

kill -HUP `cat /usr/local/nginx/logs/nginx.pid `

参考网址:

3.2 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;}

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, 已有http, 不是在server里,在server外面    upstream tomcats {         server shizhan02:8080 weight=1;#weight表示多少个        server shizhan03:8080 weight=1;        server shizhan04:8080 weight=1;}#写在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）

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

keepalived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:

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

4.4 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 

添加keepalived到开机启动 

chkconfig --add keepalived      chkconfig keepalived on

##以上所有命令一次性执行：

cp /usr/local/keepalived/sbin/keepalived /usr/sbin/cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/keepalivedcp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/ mkdir -p /etc/keepalivedcp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/keepalived.confchmod +x /etc/init.d/keepalivedchkconfig --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        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 

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，它俩完全没有任何关系。

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/bashcase "$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

#在第二台机器上添加notify.sh脚本 

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"}

#分别在两台机器上启动keepalived

service keepalived startchkconfig keepalived on