keepalived高可用

keepalived是什么keepalived是集群管理中保证集群高可用的一个服务软件，用来防止单点故障。keepalived工作原理keepalived是以VRRP协议为实现基础的，VRRP全称Virtual Router Redundancy Protocol，即虚拟路由冗余协议。虚拟路由冗余协议，可以认为是实现路由器高可用的协议，即将N台提供相同功能的路由器组成一个路由器组，这个组里面有一个master和多个backup，master上面有一个对外提供服务的vip（该路由器所在局域网内其他机器的默认路由为该vip），master会发组播，当backup收不到vrrp包时就认为master宕掉了，这时就需要根据VRRP的优先级来选举一个backup当master。这样的话就可以保证路由器的高可用了。keepalived主要有三个模块，分别是core、check和vrrp。core模块为keepalived的核心，负责主进程的启动、维护以及全局配置文件的加载和解析。check负责健康检查，包括常见的各种检查方式。vrrp模块是来实现VRRP协议的。
==============================================
脑裂  split barin：
Keepalived的BACKUP主机在收到不MASTER主机报文后就会切换成为master，如果是它们之间的通信线路出现问题，无法接收到彼此的组播通知，但是两个节点实际都处于正常工作状态，这时两个节点均为master强行绑定虚拟IP，导致不可预料的后果，这就是脑裂。
解决方式:
1、添加更多的检测手段，比如冗余的心跳线（两块网卡做健康监测），ping对方等等。尽量减少"裂脑"发生机会。(指标不治本，只是提高了检测到的概率)；
2、设置仲裁机制。两方都不可靠，那就依赖第三方。比如启用共享磁盘锁，ping网关等。(针对不同的手段还需具体分析)；
3、爆头，将master停掉。然后检查机器之间的防火墙。网络之间的通信

Nginx+keepalived实现七层的负载均衡

配置安装nginx 所有的机器，关闭防火墙和selinux
[root@proxy-master ~]# systemctl stop firewalld         //关闭防火墙
[root@proxy-master ~]# sed -i 's/^SELINUX=.*/SELINUX=disabled/' /etc/sysconfig/selinux        //关闭selinux，重启生效
[root@proxy-master ~]# setenforce 0        　　　　　　　　//关闭selinux，临时生效安装nginx， 全部4台
[root@proxy-master ~]# cd /etc/yum.repos.d/
[root@proxy-master yum.repos.d]# vim nginx.repo
[nginx-stable]
name=nginx stable repo
baseurl=http://nginx.org/packages/centos/$releasever/$basearch/
gpgcheck=0
enabled=1
[root@proxy-master yum.repos.d]# yum install yum-utils -y
[root@proxy-master yum.repos.d]# yum install nginx -y

一、实施过程 
1、选择两台nginx服务器作为代理服务器。
2、给两台代理服务器安装keepalived制作高可用生成VIP
3、配置nginx的负载均衡
# 两台配置完全一样
[root@proxy-master ~]# vim /etc/nginx/nginx.conf
user nginx;
worker_processes auto;
error_log /var/log/nginx/error.log;
pid /run/nginx.pid;
include /usr/share/nginx/modules/*.conf;
events {worker_connections 1024;
}
http {log_format  main  '$remote_addr - $remote_user [$time_local] "$request" ''$status $body_bytes_sent "$http_referer" ''"$http_user_agent" "$http_x_forwarded_for"';access_log  /var/log/nginx/access.log  main;sendfile            on;tcp_nopush          on;tcp_nodelay         on;keepalive_timeout   65;types_hash_max_size 2048;include             /etc/nginx/mime.types;default_type        application/octet-stream;include /etc/nginx/conf.d/*.conf;upstream backend {server 172.16.147.154:80 weight=1 max_fails=3 fail_timeout=20s;server 172.16.147.153:80 weight=1 max_fails=3 fail_timeout=20s;}server {listen       80;server_name  localhost;location / {proxy_pass http://backend;proxy_set_header Host $host:$proxy_port;proxy_set_header X-Forwarded-For $remote_addr;}}
}

keepalived是实现调度HA


注：主/备调度器均能够实现正常调度
1. 主/备调度器安装软件
[root@proxy-master ~]# yum install -y keepalived
[root@proxy-slave ~]# yum install -y keepalived
[root@proxy-master ~]# cp /etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf.bak
[root@proxy-master ~]# vim /etc/keepalived/keepalived.conf
! Configuration File for keepalivedglobal_defs {router_id directory1   #辅助改为directory2
}vrrp_instance VI_1 {state MASTER        #定义主还是备interface ens33     #VIP绑定接口virtual_router_id 80  #整个集群的调度器一致priority 100         #back改为50advert_int 1authentication {auth_type PASSauth_pass 1111}virtual_ipaddress {172.16.147.100/24   # vip}
}[root@proxy-slave ~]# cp /etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf.bak
[root@proxy-slave ~]# vim /etc/keepalived/keepalived.conf
! Configuration File for keepalivedglobal_defs {router_id directory2
}vrrp_instance VI_1 {state BACKUP    #设置为backupinterface ens33nopreempt        #设置到back上面，不抢占资源virtual_router_id 80priority 50   #辅助改为50advert_int 1authentication {auth_type PASSauth_pass 1111}virtual_ipaddress {172.16.147.100/24}
}
3. 启动KeepAlived（主备均启动）
[root@proxy-master ~]# systemctl enable keepalived
[root@proxy-slave ~]# systemctl start keepalived
[root@proxy-master ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00inet 127.0.0.1/8 scope host lovalid_lft forever preferred_lft foreverinet 172.16.147.100/32 scope global lovalid_lft forever preferred_lft foreverinet6 ::1/128 scope host valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000link/ether 00:0c:29:ec:8a:fe brd ff:ff:ff:ff:ff:ffinet 172.16.147.155/24 brd 172.16.147.255 scope global noprefixroute dynamic ens33valid_lft 1115sec preferred_lft 1115secinet 172.16.147.101/24 scope global secondary ens33valid_lft forever preferred_lft forever到此：
可以解决心跳故障keepalived
不能解决Nginx服务故障
4. 扩展对调度器Nginx健康检查（可选）两台都设置
思路：
让Keepalived以一定时间间隔执行一个外部脚本，脚本的功能是当Nginx失败，则关闭本机的Keepalived
(1) script
[root@proxy-master ~]# vim /etc/keepalived/check_nginx_status.sh
#!/bin/bash												        
/usr/bin/curl -I http://localhost &>/dev/null	
if [ $? -ne 0 ];then										    
#	/etc/init.d/keepalived stopsystemctl stop keepalived
fi															        	
[root@proxy-master ~]# chmod a+x /etc/keepalived/check_nginx_status.sh(2). keepalived使用script
! Configuration File for keepalivedglobal_defs {router_id director1
}
vrrp_script check_nginx {script "/etc/keepalived/check_nginx_status.sh"interval 5
}vrrp_instance VI_1 {state MASTERinterface ens33virtual_router_id 80priority 100advert_int 1authentication {auth_type PASSauth_pass 1111}virtual_ipaddress {192.168.246.16/24}track_script {check_nginx}
}
注：必须先启动nginx，再启动keepalived

keepalived高可用

Nginx+keepalived实现七层的负载均衡

相关文章

安装MySQL驱动程序笔记一

Django一分钟：借助Django的认证系统快速实现RBAC权限校验以及Session会话

Java String trim()方法

SAP B1 Web Client MS Teams App集成连载三

热题系列章节20

python异常处理知识简记

《机器人SLAM导航核心技术与实战》第1季：第9章_视觉SLAM系统

聚焦API安全未来，F5打造无缝集成的解决方案