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：http://nginx.org/
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（/usr/local/nginx/conf下的nginx.conf文件）
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upstream myproject{
#server 183.232.41.1;
server 42.156.140.7;
server 61.129.48.158;
}
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;](http://192.168.0.21:8080/) #这里是代理走向的目标服务器：tomcat
#proxy_pass http://myproject;
}
}
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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
或者
/usr/local/nginx/sbin/nginx -s reload;
3.2. 动静分离
动态资源 index.jsp
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location ~ .*.(jsp|do|action)$ {
proxy_pass http://tomcat-01.itcast.cn:8080;
}
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静态资源
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location ~ .*.(html|js|css|gif|jpg|jpeg|png)$ {
expires 3d;
}
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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。
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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;
}
卸载server里
location ~ .*.(jsp|do|action) {
proxy_pass [http://tomcats;](http://blog.51cto.com/yushiwh/1906974) #tomcats是后面的tomcat服务器组的逻辑组号
}
}
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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
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
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
以上所有命令一次性执行：
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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
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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
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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
}
}
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BACKUP节点
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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
}
}
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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
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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"
}
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添加切换通知脚本
vi /usr/local/keepalived/sbin/notify.sh
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!/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
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添加执行权限
chmod +x /usr/local/keepalived/sbin/notify.sh
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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"
}
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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