Nginx&&Keepalived（一）Keepalived介绍

一、背景：

案例1：如现有服务my-service-demo，希望实现高可用和负载均衡：

首先，my-service-demo服务部署在两台机器上，通过nginx去代理这两个节点，负载均衡就实现了。如果只有一个nginx，这台nginx机器一旦宕机，访问nginx会报错。这时候在另外一台机器nginx2上也安装nginx，并配置同样的代理，可以解决上述问题，但是暴露给用户的只有一个域名（或ip），不可能给用户提供两个域名，域名1（nginx机器1）访问不了了再让用户访问域名2（nginx机器2），这时候就可以使用keepalived将nginx机器1和nginx机器2封装成一个Vritrual IP（虚拟ip），把这个虚拟ip暴露给用户实现高可用。

再如，前后端分离项目，后端地址在nginx中做负载均衡代理，前端访问upstream代理的域名，再由一个虚拟ip代理前端页面实现高可用：

案例2：再如mysql配置主从数据库，主库可写，从库只读。项目里面需要配置主库的地址，如果主库挂了，从库切为主库，则需要改代码配置，并且需要重启项目比较麻烦。这时候可以把主从库绑定成一个vip提供给项目连接。如果主从库切换，只需要改动keepalived的配置，不需要改代码。

二、Keepalived下载与安装（linux环境）：

方法一：yum方式

1、yum安装：

安装依赖包
[root@localhost ~]# yum install -y curl gcc openssl-devel libnl3-devel net-snmp-devel
[root@localhost ~]# yum install -y keepalived

2、初始化及启动：

[root@localhost ~]# systemctl start keepalived   //启动keepalived
[root@localhost ~]# systemctl enable keepalived  //加入开机启动keepalived
[root@localhost ~]# systemctl restart keepalived  //重新启动keepalived
[root@localhost ~]# systemctl status keepalived   //查看keepalived状态

 方法二：源码包

1、官网下载keepalived的最新版本，解压并安装：

[root@master src]# pwd
/usr/local/src
[root@master src]# wget http://www.keepalived.org/software/keepalived-2.0.7.tar.gz
[root@master src]# tar xvf keepalived-2.0.7.tar.gz
[root@master src]# cd keepalived-2.0.7
[root@master keepalived-2.0.7]# ./configure --prefix=/usr/local/keepalived
[root@master keepalived-2.0.7]# make && make install

 完成后会在以下路径生成：

/usr/local/keepalived/etc/keepalived/keepalived.conf
/usr/local/keepalived/etc/sysconfig/keepalived
/usr/local/keepalived/sbin/keepalived

 2、初始化及启动：依次执行以下命令

# keepalived启动脚本变量引用文件，默认文件路径是/etc/sysconfig/，也可以不做软链接，直接修改启动脚本中文件路径即可（安装目录下）
[root@localhost /]# cp /usr/local/keepalived/etc/sysconfig/keepalived  /etc/sysconfig/keepalived 
 
# 将keepalived主程序加入到环境变量（安装目录下）
[root@localhost /]# cp /usr/local/keepalived/sbin/keepalived /usr/sbin/keepalived
 
# keepalived启动脚本（源码目录下），放到/etc/init.d/目录下就可以使用service命令便捷调用
[root@localhost /]# cp /usr/local/src/keepalived-2.0.7/keepalived/etc/init.d/keepalived  /etc/init.d/keepalived
 
# 将配置文件放到默认路径下
[root@localhost /]# mkdir /etc/keepalived
[root@localhost /]# cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf

 最后执行启动、关闭、重启命令：service keepalived start|stop|restart 

三、Keepalived介绍：

安装后默认配置文件：

! Configuration File for keepalived

global_defs {
   notification_email {
     [email protected]
     [email protected]
     [email protected]
   }
   notification_email_from [email protected]
   smtp_server 192.168.200.1
   smtp_connect_timeout 30
   router_id LVS_DEVEL
   vrrp_skip_check_adv_addr
   vrrp_strict
   vrrp_garp_interval 0
   vrrp_gna_interval 0
}

vrrp_instance VI_1 {
    state MASTER
    interface eth0
    virtual_router_id 51
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        192.168.200.16
        192.168.200.17
        192.168.200.18
    }
}

virtual_server 192.168.200.100 443 {
    delay_loop 6
    lb_algo rr
    lb_kind NAT
    persistence_timeout 50
    protocol TCP

    real_server 192.168.201.100 443 {
        weight 1
        SSL_GET {
            url {
              path /
              digest ff20ad2481f97b1754ef3e12ecd3a9cc
            }
            url {
              path /mrtg/
              digest 9b3a0c85a887a256d6939da88aabd8cd
            }
            connect_timeout 3
            retry 3
            delay_before_retry 3
        }
    }
}

virtual_server 10.10.10.2 1358 {
    delay_loop 6
    lb_algo rr
    lb_kind NAT
    persistence_timeout 50
    protocol TCP

    sorry_server 192.168.200.200 1358

    real_server 192.168.200.2 1358 {
        weight 1
        HTTP_GET {
            url {
              path /testurl/test.jsp
              digest 640205b7b0fc66c1ea91c463fac6334d
            }
            url {
              path /testurl2/test.jsp
              digest 640205b7b0fc66c1ea91c463fac6334d
            }
            url {
              path /testurl3/test.jsp
              digest 640205b7b0fc66c1ea91c463fac6334d
            }
            connect_timeout 3
            retry 3
            delay_before_retry 3
        }
    }

    real_server 192.168.200.3 1358 {
        weight 1
        HTTP_GET {
            url {
              path /testurl/test.jsp
              digest 640205b7b0fc66c1ea91c463fac6334c
            }
            url {
              path /testurl2/test.jsp
              digest 640205b7b0fc66c1ea91c463fac6334c
            }
            connect_timeout 3
            retry 3
            delay_before_retry 3
        }
    }
}

virtual_server 10.10.10.3 1358 {
    delay_loop 3
    lb_algo rr
    lb_kind NAT
    persistence_timeout 50
    protocol TCP

    real_server 192.168.200.4 1358 {
        weight 1
        HTTP_GET {
            url {
              path /testurl/test.jsp
              digest 640205b7b0fc66c1ea91c463fac6334d
            }
            url {
              path /testurl2/test.jsp
              digest 640205b7b0fc66c1ea91c463fac6334d
            }
            url {
              path /testurl3/test.jsp
              digest 640205b7b0fc66c1ea91c463fac6334d
            }
            connect_timeout 3
            retry 3
            delay_before_retry 3
        }
    }

    real_server 192.168.200.5 1358 {
        weight 1
        HTTP_GET {
            url {
              path /testurl/test.jsp
              digest 640205b7b0fc66c1ea91c463fac6334d
            }
            url {
              path /testurl2/test.jsp
              digest 640205b7b0fc66c1ea91c463fac6334d
            }
            url {
              path /testurl3/test.jsp
              digest 640205b7b0fc66c1ea91c463fac6334d
            }
            connect_timeout 3
            retry 3
            delay_before_retry 3
        }
    }
}