1. 课程目标
1.1. 了解反向代理和负载均衡的概念
1.2. 掌握Nginx的安装和使用
1.3. 利用Nginx实现负载均衡
2. Nginx相关概念
2.1. 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。
2.2. 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。
3. Nginx的安装
3.1. 下载nginx
3.2. 上传并解压nginx
tar -zxvf nginx-1.8.1.tar.gz -C /usr/local/src
3.3. 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
4. 配置nginx
4.1. 配置反向代理
1.修改nginx配置文件
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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:http://www.cnblogs.com/jianxie/p/3990377.html
4.2. 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; } |
#静态资源
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location ~ .*.(html|js|css|gif|jpg|jpeg|png)$ { expires 3d; } |
4.3. 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; #tomcats是后面的tomcat服务器组的逻辑组号 } } |
5. 利用keepalived实现高可靠（HA）
5.1. 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。
5.2. 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。
5.3. 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
5.4. 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 |
添加keepalived到开机启动
chkconfig --add keepalived
chkconfig keepalived on
5.5. 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 } } |
#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 } } |
#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
5.6. 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" } |
#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 |
#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" } |
#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