Keepalived - Keepalived 实现 tomcat双机热备
文章目录
- Pre
- 环境信息
- 官网
- 原理
- keepalived 安装
- 137 安装 keepalived
- 138 安装 keepalived
- 配置keepalived的配置文件/etc/keepalived/keepalived.conf
- 关键参数解读
- 137
- 138
- 检测脚本
- 日志
- 状态发生变更,触发脚本
- 小结
- Questions
- exited due to signal 15
- notify_master notify_backup未生效
Pre
双机热备是指两台机器都在运行,但并不是两台机器都同时在提供服务。
环境信息
节点 | 软件 | IP |
---|---|---|
节点A | keepalived + tomcat | 192.168.126.137 |
节点B | keepalived + tomcat | 192.168.126.138 |
虚拟IP | - | 192.168.126.200 |
官网
https://keepalived.readthedocs.io/en/latest/#
原理
keepalived用于保证环境高可用,防止单点故障。
keepalived主要有三个模块,分别是core、check和VRRP。
- core核心模块,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模块实现VRRP协议
VRRP(Virtual Router Redundancy Protocol) 即虚拟路由冗余协议,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 安装
两个节点均需要安装, 在137 和 138 节点上安装 ,执行 yum install keepalived
137 安装 keepalived
[root@localhost ~]# yum install keepalived
Loaded plugins: fastestmirror
.......
....... Complete!
[root@localhost ~]#
138 安装 keepalived
[root@localhost ~]# yum install keepalived
Loaded plugins: fastestmirror
.......
....... Complete!
[root@localhost ~]#
tomcat 也都装下哈 ,用于验证,可以yum安装
CentOS 7 yum安装与配置 Tomcat 写的挺不错,没有的话可以参考
配置keepalived的配置文件/etc/keepalived/keepalived.conf
关键参数解读
state 主服务器为MASTER,其他服务器均为BACKUP
interface 通信用的网卡,ip addr可以查看,以实际为准
virtual_router_id 主从服务器此ID必须一致
priority 优先级,主服务器必须大于其他服务器,数值越大优先级越高
authentication 主从服务器必须一致
virtual_ipaddress 虚拟IP地址,主从服务器必须一致,该VIP为客户端访问时使用的IP
137
! Configuration File for keepalived
global_defs {notification_email {acassen@firewall.locfailover@firewall.locsysadmin@firewall.loc}notification_email_from example@example.comsmtp_server mail.example.comsmtp_connect_timeout 30router_id LVS_DEVEL
}
vrrp_script chk_tomcat {script "/etc/keepalived/tomcat_check.sh"interval 5weight -5fall 3 rise 2
}
vrrp_instance VI_1 {state MASTERinterface ens33mcast_src_ip 192.168.126.137virtual_router_id 51priority 101advert_int 2authentication {auth_type PASSauth_pass 1111}virtual_ipaddress {192.168.126.200}track_script {chk_tomcat}
}
138
! Configuration File for keepalived
global_defs {notification_email {acassen@firewall.locfailover@firewall.locsysadmin@firewall.loc}notification_email_from example@example.comsmtp_server mail.example.comsmtp_connect_timeout 30router_id LVS_DEVEL
}
vrrp_script chk_tomcat {script "/etc/keepalived/tomcat_check.sh"interval 5weight -5fall 3 rise 2
}
vrrp_instance VI_1 {state BACKUPinterface ens33mcast_src_ip 192.168.126.138virtual_router_id 51priority 99advert_int 2authentication {auth_type PASSauth_pass 1111}virtual_ipaddress {192.168.126.200}track_script {chk_tomcat}
}
与主节点的配置上的区别,需要注意
state 表示一个是主机一个是备机,mcast_src_ip 当前服务器的ip,priority 主机要比备机的要高
检测脚本
!/bin/bash
JAVA_PROCESS=`ps -C java --no-heading| wc -l`
if [ $JAVA_PROCESS -eq 0 ];thenecho "tomcat is stop"sleep 2if [ `ps -C java --no-heading| wc -l` -eq 0 ];thensystemctl stop keepalived.service fi
fi
比较简单,根据实际情况调整
检测是否有tomcat在运行,如果没有的话,等2秒,如果还没有就把keepalived给停止掉,这样vip就能从主机master切换到备机BACKUP上了。
日志
可以查看 /var/log/messages 日志 观察切换和选主的过程。
状态发生变更,触发脚本
https://keepalived.readthedocs.io/en/latest/configuration_synopsis.html
! Configuration File for keepalived
global_defs {notification_email {acassen@firewall.locfailover@firewall.locsysadmin@firewall.loc}notification_email_from example@example.comsmtp_server mail.example.comsmtp_connect_timeout 30router_id LVS_DEVEL
}vrrp_script chk_tomcat {script "/etc/keepalived/tomcat_check.sh"interval 5weight -5fall 3 rise 2
}
vrrp_instance VI_1 {state MASTERinterface ens33mcast_src_ip 192.168.126.137virtual_router_id 51priority 101advert_int 2authentication {auth_type PASSauth_pass 1111}virtual_ipaddress {192.168.126.200}track_script {chk_tomcat}notify_master /etc/keepalived/a.sh notify_backup /etc/keepalived/b.sh
当节点从BACKUP 转为 MASTER的时候 ,执行 /etc/keepalived/a.sh
当节点从MASTER 转为 BACKUP的时候 ,执行 /etc/keepalived/b.sh
小结
MASTER和 BACKUP,预先分配好, 通过priority 来确定, 当MASTER宕机以后,BACKUP 没有收到 MASTER的 VRRP消息,BACKUP就认为 MASTER宕机了,这个时候就把自己选举为MASTER。
MASTER宕机,本节点的日志
Dec 30 01:40:01 localhost Keepalived[6784]: Stopping
Dec 30 01:40:01 localhost systemd: Stopping LVS and VRRP High Availability Monitor...
Dec 30 01:40:01 localhost Keepalived_vrrp[6786]: VRRP_Instance(VI_1) sent 0 priority
Dec 30 01:40:01 localhost Keepalived_vrrp[6786]: VRRP_Instance(VI_1) removing protocol VIPs.
Dec 30 01:40:01 localhost Keepalived_healthcheckers[6785]: Stopped
Dec 30 01:40:02 localhost Keepalived_vrrp[6786]: Stopped
Dec 30 01:40:02 localhost Keepalived[6784]: Stopped Keepalived v1.3.5 (03/19,2017), git commit v1.3.5-6-g6fa32f2
Dec 30 01:40:02 localhost systemd: Stopped LVS and VRRP High Availability Monitor.
BACKUP节点的日志
Dec 30 01:40:05 localhost Keepalived_vrrp[9173]: VRRP_Instance(VI_1) Entering MASTER STATE
Dec 30 01:40:05 localhost Keepalived_vrrp[9173]: VRRP_Instance(VI_1) setting protocol VIPs.
当MASTER恢复以后,MASTER发送VRRP消息给BACKUP,这个时候虽然BACKUP是MASTER,但是 比较Prority后,发现自己的Prority小,会进入BACKUP模式,这个时候,之前设置的MASTER就又变成了MASTER了 。
MASTER恢复,本节点的日志
Dec 30 01:42:09 localhost Keepalived[6915]: Starting Healthcheck child process, pid=6916
Dec 30 01:42:09 localhost Keepalived[6915]: Starting VRRP child process, pid=6917
Dec 30 01:42:09 localhost Keepalived_healthcheckers[6916]: Opening file '/etc/keepalived/keepalived.conf'.
Dec 30 01:42:09 localhost systemd: Started LVS and VRRP High Availability Monitor.
Dec 30 01:42:09 localhost Keepalived_vrrp[6917]: Registering Kernel netlink reflector
Dec 30 01:42:09 localhost Keepalived_vrrp[6917]: Registering Kernel netlink command channel
Dec 30 01:42:09 localhost Keepalived_vrrp[6917]: Registering gratuitous ARP shared channel
Dec 30 01:42:09 localhost Keepalived_vrrp[6917]: Opening file '/etc/keepalived/keepalived.conf'.
Dec 30 01:42:09 localhost Keepalived_vrrp[6917]: WARNING - default user 'keepalived_script' for script execution does not exist - please create.
Dec 30 01:42:09 localhost Keepalived_vrrp[6917]: SECURITY VIOLATION - scripts are being executed but script_security not enabled.
Dec 30 01:42:09 localhost Keepalived_vrrp[6917]: VRRP_Instance(VI_1) removing protocol VIPs.
Dec 30 01:42:09 localhost Keepalived_vrrp[6917]: Using LinkWatch kernel netlink reflector...
Dec 30 01:42:09 localhost Keepalived_vrrp[6917]: VRRP sockpool: [ifindex(2), proto(112), unicast(0), fd(10,11)]
Dec 30 01:42:09 localhost Keepalived_vrrp[6917]: VRRP_Script(chk_tomcat) succeeded
Dec 30 01:42:10 localhost Keepalived_vrrp[6917]: VRRP_Instance(VI_1) Transition to MASTER STATE
Dec 30 01:42:12 localhost Keepalived_vrrp[6917]: VRRP_Instance(VI_1) Entering MASTER STATE
Dec 30 01:42:12 localhost Keepalived_vrrp[6917]: VRRP_Instance(VI_1) setting protocol VIPs.
Dec 30 01:42:12 localhost Keepalived_vrrp[6917]: Sending gratuitous ARP on ens33 for 192.168.126.200
BACKUP节点的日志
Dec 30 01:42:09 localhost Keepalived_vrrp[9173]: /etc/keepalived/tomcat_check.sh exited with status 127
Dec 30 01:42:12 localhost Keepalived_vrrp[9173]: VRRP_Instance(VI_1) Received advert with higher priority 101, ours 94
Dec 30 01:42:12 localhost Keepalived_vrrp[9173]: VRRP_Instance(VI_1) Entering BACKUP STATE
Dec 30 01:42:12 localhost Keepalived_vrrp[9173]: VRRP_Instance(VI_1) removing protocol VIPs.
Questions
exited due to signal 15
/var/log/messages 日志提示:/etc/keepalived/check_nginx.sh exited due to signal 15
调整如下参数
interval 5 #监控脚本的执行时间要大于advert_int advert_int 2 #心跳检查间隔时间
notify_master notify_backup未生效
检查 getenforce
getenforce 如果 开启的话,关闭 执行 setenforce 0
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