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高可用：两台业务系统启动着相同的服务，如果有一台故障，另一台自动接管,我们将将这个称之为高可用；
Keekpalived工作原理：通过vrrp协议实现
vrrp原理
vrrp抓包
Keepalived工作方式：抢占式、非抢占式
安装：yum install keepalived -y
日志存放位置：/var/log/messages
1、keepaliaved 抢占式配置
master配置
[root@lb01 ~]# rpm-qc keepalived/etc/keepalived/keepalived.conf/etc/sysconfig/keepalived[root@lb01 ~]# cat/etc/keepalived/keepalived.conf!Configuration Fileforkeepalivedglobal_defs{router_id lb02 #标识信息，一个名字而已；}vrrp_instance VI_1{state MASTER #角色是masterinterfaceeth0 #vip 绑定端口 virtual_router_id50#让master 和backup在同一个虚拟路由里，id 号必须相同； priority150#优先级,谁的优先级高谁就是master;advert_int1#心跳间隔时间 authentication{auth_type PASS #认证 auth_pass1111#密码}virtual_ipaddress{10.0.0.3#虚拟ip}}
backup配置
[root@lb02 ~]# cat/etc/keepalived/keepalived.conf!Configuration Fileforkeepalivedglobal_defs{router_id lb02}vrrp_instance VI_1{state BACKUPinterfaceeth0 virtual_router_id50priority100advert_int1authentication{auth_type PASS auth_pass1111}virtual_ipaddress{10.0.0.3}}[root@lb02 ~]#
2、Keepalived非抢占式配置：
非抢占式不再有主从之分，全部都为BACKUP,并且配置文件中添加nopreempt，用来标识为非抢占式；
[root@lb01/etc/nginx/upstream]# cat/etc/keepalived/keepalived.conf!Configuration Fileforkeepalivedglobal_defs{router_id lb01}vrrp_instance VI_1{state MASTERinterfaceeth0 virtual_router_id50priority150advert_int1authentication{auth_type PASS auth_pass1111}virtual_ipaddress{10.0.0.3}}
[root@lb02/etc/nginx/upstream]# cat/etc/keepalived/keepalived.conf!Configuration Fileforkeepalivedglobal_defs{router_id lb02}vrrp_instance VI_1{state BACKUPinterfaceeth0 virtual_router_id50priority100nopreempt advert_int1authentication{auth_type PASS auth_pass1111}virtual_ipaddress{10.0.0.3}}You havenewmail in/var/spool/mail/root[root@lb02/etc/nginx/upstream]#
3、nginx+keepalived
实现思路：将keepalived 中的vip作为nginx负载均衡的监听地址，并且域名绑定的也是vip的地址。
说明：Nginx 负载均衡实现高可用，需要借助Keepalived地址漂移功能。
在不考虑后端数据库和存储的时候如下架构
keepalived+Nginx
两台负载均衡配置：
[root@lb01/etc/nginx/upstream]# ip add show eth02:eth0:<BROADCAST,MULTICAST,UP,LOWER_UP>mtu1500qdisc pfifo_fast state UP groupdefaultqlen1000link/ether00:0c:29:97:e1:ff brd ff:ff:ff:ff:ff:ff inet10.0.0.5/24brd10.0.0.255scope global eth0 valid_lft forever preferred_lft forever inet10.0.0.3/32scope global eth0 valid_lft forever preferred_lft forever inet6 fe80::20c:29ff:fe97:e1ff/64scope link valid_lft forever preferred_lft forever[root@lb01/etc/nginx/upstream]# cat/etc/keepalived/keepalived.conf!Configuration Fileforkeepalivedglobal_defs{router_id lb01}vrrp_instance VI_1{state MASTERinterfaceeth0 virtual_router_id50priority150advert_int1authentication{auth_type PASS auth_pass1111}virtual_ipaddress{10.0.0.3}}[root@lb01/etc/nginx/upstream]#
[root@lb02/etc/nginx/upstream]# ip add show eth02:eth0:<BROADCAST,MULTICAST,UP,LOWER_UP>mtu1500qdisc pfifo_fast state UP groupdefaultqlen1000link/ether00:0c:29:6f:18:48brd ff:ff:ff:ff:ff:ff inet10.0.0.6/24brd10.0.0.255scope global eth0 valid_lft forever preferred_lft forever inet6 fe80::20c:29ff:fe6f:1848/64scope link valid_lft forever preferred_lft forever[root@lb02/etc/nginx/upstream]# cat/etc/keepalived/keepalived.conf!Configuration Fileforkeepalivedglobal_defs{router_id lb02}vrrp_instance VI_1{state BACKUPinterfaceeth0 virtual_router_id50priority100nopreempt advert_int1authentication{auth_type PASS auth_pass1111}virtual_ipaddress{10.0.0.3}}[root@lb02/etc/nginx/upstream]#
4、keepalived脑裂现象
由于某些原因，导致两台keepalived高可用服务器在指定时间内，无法检测到对方存活心跳信息，从而导致互相抢占对方的资源和服务所有权，然而此时两台高可用服务器有都还存活。
可能出现的原因：
1、服务器网线松动等网络故障；
2、服务器硬件故障发生损坏现象而崩溃；
3、主备都开启了firewalld 防火墙。
4、在Keepalived+nginx 架构中，当Nginx宕机，会导致用户请求失败，但是keepalived不会进行切换，
所以需要编写一个检测nginx的存活状态的脚本，如果nginx不存活，则kill掉宕掉的nginx主机上面的keepalived。(所有的keepalived都要配置)
架构如下：
image.png
脚本如下：
[root@lb01/server/scripts]# cat/server/scripts/check_list #!/bin/shnginxpid=$(ps-C nginx--no-header|wc-l)#1.判断Nginx是否存活,如果不存活则尝试启动Nginxif[$nginxpid-eq0];then systemctl start nginx sleep3#2.等待3秒后再次获取一次Nginx状态 nginxpid=$(ps-C nginx--no-header|wc-l)#3.再次进行判断,如Nginx还不存活则停止Keepalived,让地址进行漂移,并退出脚本if[$nginxpid-eq0];then systemctl stop keepalived fifi[root@lb01/server/scripts]#
配置文件如下：
[root@lb01/server/scripts]# cat/etc/keepalived/keepalived.conf!Configuration Fileforkeepalivedglobal_defs{router_id lb01}vrrp_script check{script"/server/scripts/check_list"interval10}vrrp_instance VI_1{state MASTERinterfaceeth0 virtual_router_id50priority150advert_int1authentication{auth_type PASS auth_pass1111}virtual_ipaddress{10.0.0.3}track_script{check}}[root@lb01/server/scripts]#
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作者：你好_请关照
链接：https://www.jianshu.com/p/a6b5ab36292a
来源：简书
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