linux学习第五十六篇:集群介绍,keepalived介绍,用keepalived配置高可用集群
2018-01-22 16:49
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集群介绍
根据功能划分为两大类:高可用和负载均衡。高可用集群通常为两台服务器,一台工作,另外一台作为冗余,当提供服务的机器宕机,冗余将接替继续提供服务。实现高可用的开源软件有:heartbeat、keepalived。负载均衡集群,需要有一台服务器作为分发器,它负责把用户的请求分发给后端的服务器处理,在这个集群里,除了分发器外,就是给用户提供服务的服务器了,这些服务器数量至少为2。实现负载均衡的开源软件有LVS、keepalived、haproxy、nginx,商业的有F5、Netscalerkeepalived介绍
在这里我们使用keepalived来实现高可用集群,因为heartbeat在centos6上有一些问题,影响实验效果keepalived通过VRRP(Virtual Router Redundancy Protocl)来实现高可用。
在这个协议里会将多台功能相同的路由器组成一个小组,这个小组里会有1个master角色和N(N>=1)个backup角色。
master会通过组播的形式向各个backup发送VRRP协议的数据包,当backup收不到master发来的VRRP数据包时,就会认为master宕机了。此时就需要根据各个backup的优先级来决定谁成为新的mater。
Keepalived要有三个模块,分别是core、check和vrrp。其中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模块负责健康检查,vrrp模块是来实现VRRP协议的。
用keepalived配置高可用集群
准备两台机器,一台作为master,一台作为backup两台机器都执行:
yum install -y keepalived
两台机器都安装nginx,其中master上已经编译安装过nginx,backup上需要yum安装nginx: yum install -y nginx
master上
重新编辑master上keepalived配置文件 vim /etc/keepalived/keepalived.conf ,把原配置文件内容清空,加入如下内容:global_defs { notification_email { aming@aminglinux.com //出现问题时给指定邮箱发邮件 } notification_email_from root@aminglinux.com //由哪一个邮件发出去 smtp_server 127.0.0.1 smtp_connect_timeout 30 router_id LVS_DEVEL } vrrp_script chk_nginx { script "/usr/local/sbin/check_ng.sh" //检测服务是否正常 interval 3 //检测间断3秒钟 } vrrp_instance VI_1 { state MASTER interface ens33 //通过vrrp协议去发广播,通过指定网卡去发,这里的网卡是ens33 virtual_router_id 51 //定义路由器的ID priority 100 advert_int 1 authentication { //认证相关的信息 auth_type PASS auth_pass aminglinux>com } virtual_ipaddress { //VIP,如果主宕机了,从马上绑定定义的这个VIP 192.168.188.100 //这个IP可以在主上用ip add命令查看 } track_script { chk_nginx //加载检查脚本 } }
master编辑监控脚本 vim /usr/local/sbin/check_ng.sh 路径在keepalived配置文件已定义的:
#!/bin/bash #时间变量,用于记录日志 d=`date --date today +%Y%m%d_%H:%M:%S` #计算nginx进程数量 n=`ps -C nginx --no-heading|wc -l` #如果进程为0,则启动nginx,并且再次检测nginx进程数量, #如果还为0,说明nginx无法启动,此时需要关闭keepalived if [ $n -eq "0" ]; then /etc/init.d/nginx start n2=`ps -C nginx --no-heading|wc -l` if [ $n2 -eq "0" ]; then echo "$d nginx down,keepalived will stop" >> /var/log/check_ng.log systemctl stop keepalived fi fi
给脚本755权限:
chmod 755 /usr/local/sbin/check_ng.sh
master启动服务
systemctl start keepalived
backup上
backup上编辑配置文件 vim /etc/keepalived/keepalived.confglobal_defs { notification_email { aming@aminglinux.com } notification_email_from root@aminglinux.com smtp_server 127.0.0.1 smtp_connect_timeout 30 router_id LVS_DEVEL } vrrp_script chk_nginx { script "/usr/local/sbin/check_ng.sh" interval 3 } vrrp_instance VI_1 { state BACKUP interface ens33 virtual_router_id 51 priority 90 //主上是100,这里是90,优先级 advert_int 1 authentication { auth_type PASS auth_pass aminglinux>com } virtual_ipaddress { 192.168.188.100 //跟主上的IP一样 } track_script { chk_nginx } }
backup上编辑监控脚本 vim /usr/local/sbin/check_ng.sh
#时间变量,用于记录日志 d=`date --date today +%Y%m%d_%H:%M:%S` #计算nginx进程数量 n=`ps -C nginx --no-heading|wc -l` #如果进程为0,则启动nginx,并且再次检测nginx进程数量, #如果还为0,说明nginx无法启动,此时需要关闭keepalived if [ $n -eq "0" ]; then systemctl start nginx n2=`ps -C nginx --no-heading|wc -l` if [ $n2 -eq "0" ]; then echo "$d nginx down,keepalived will stop" >> /var/log/check_ng.log systemctl stop keepalived fi fi
给脚本755权限
chmod 755 /usr/local/sbin/check_ng.sh
backup上也启动服务
systemctl start keepalived
测试高可用
先确定好两台机器上nginx差异,比如可以通过curl -I 来查看nginx版本测试1:关闭master上的nginx服务
测试2:在master上增加iptabls规则
iptables -I OUTPUT -p vrrp -j DROP
测试3:关闭master上的keepalived服务
VIP这个IP会被释放,backup上就会获取到这个VIP
测试4:启动master上的keepalived服务
VIP会被重新获取
扩展
heartbeat和keepalived比较http://blog.csdn.net/yunhua_lee/article/details/9788433
DRBD工作原理和配置 http://502245466.blog.51cto.com/7559397/1298945
mysql+keepalived http://lizhenliang.blog.51cto.com/7876557/1362313
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