linux集群-keepalived介绍-用keepalived配置高可用集群
2018-09-05 21:41
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linux集群介绍:
以功能划分: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。实现高可用的开源软件有:heartbeat、keepalived
负载均衡集群:一台服务器作为分发器,负责把用户的请求分发给后端的服务器处理,后端服务器数量至少为2 。实现负载均衡的开源软件有LVS、keepalived、haproxy、nginx,商业的有F5、Netscaler
keepalived介绍:
keepalived通过VRRP(Virtual Router Redundancy Protocl:虚拟路由冗余协议)来实现高可用(HA,又叫做双机热备)。定义多台功能相同的机器组成小组,小组有1个master角色和N(N>=1)个backup角色,master以组播的形式向backup发送VRRP协议的数据包,当backup收不到VRRP数据包时,会认为master宕机了。此时根据各个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:
1.准备操作:两台机器192.168.1.100(master) 和192.168.1.101(backup);均安装keepalived和nginx(nginx服务是实现高可用的实验对象):yum install -y keepalived nginx;并启动nginx服务;检查两台机器防火墙和selinux服务是否已关闭
2.master修改keepalived配置:
vim /etc/keepalived/keepalived.conf #可将原有配置备份,全新添加以下内容:
global_defs { notification_email { #出现问题时发送信息到该邮箱;可以不用定义 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 { #检测nginx服务是否正常 script "/usr/local/sbin/check_ng.sh" #定义脚本路径,该脚本需自己编写检测流程 interval 3 #检测时间间隔为3秒 } vrrp_instance VI_1 { #定义master相关 state MASTER #角色名称,此角色为master,若为backup,此处填BACKUP interface ens33 #通过该网卡发送vrrp报文 virtual_router_id 51 #主备id需要一致 priority 100 #权重 advert_int 1 authentication { #定义认证相关 auth_type PASS #密码形式 auth_pass aminglinux>com #密码为aminglinux>com } virtual_ipaddress { 192.168.1.2 #定义虚拟IP,该IP使用在工作节点上,主备定义一样 } track_script { chk_nginx #加载检查脚本chk_nginx } }
3.master上编写检测nginx服务脚本:
vim /usr/local/sbin/check_ng.sh #此路径和脚本名称在第2步定义的路径相应;添加以下内容:
#!/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
chmod 755 /usr/local/sbin/check_ng.sh #更改脚本权限
4.启动master的keepalived服务:
systemctl start keepalived #启动服务;keepalived相关日志在/var/log/messages里面
5.backup修改keepalived配置:
vim /etc/keepalived/keepalived.conf #可将原有配置备份,全新添加以下内容:
global_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 #角色名称为backup interface ens33 virtual_router_id 51 priority 90 #权重,比master低 advert_int 1 authentication { auth_type PASS auth_pass aminglinux>com } virtual_ipaddress { 192.168.2.100 } track_script { chk_nginx } }
6.backup上编写检测nginx服务脚本:
vim /usr/local/sbin/check_ng.sh #与master检测脚本一样;添加以下内容:
#!/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
chmod 755 /usr/local/sbin/check_ng.sh #更改脚本权限
7.启动master的keepalived服务:
systemctl start keepalived #启动服务;keepalived相关日志在/var/log/messages里面
8.简单测试:
测试1:手动关闭master上的nginx服务,看nginx服务能否自动开启。能则正常
测试2:master上添加iptables规则:iptables -I output -p vrrp -j DROP ,看虚拟ip是否仍然在master上,或检查虚拟IP访问的nginx默认页面是否是master的。是则正常;注意测试后清除规则。
测试3:master上关闭keepalived服务,看虚拟ip是否更换到backup上,或检查虚拟IP访问的nginx默认页面是否是backup的。是则正常
测试4:master上启动keepalived服务,看虚拟ip是否更换到master上
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