Keepalived - Keepalived 实现 tomcat双机热备

喜欢ヅ旅行 2022-12-31 13:22 357阅读 0赞

### 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 #

<table> 
 <thead> 
  <tr> 
   <th align="center">节点</th> 
   <th align="right">软件</th> 
   <th align="right">IP</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="center">节点A</td> 
   <td align="right">keepalived + tomcat</td> 
   <td align="right">192.168.126.137</td> 
  </tr> 
  <tr> 
   <td align="center">节点B</td> 
   <td align="right">keepalived + tomcat</td> 
   <td align="right">192.168.126.138</td> 
  </tr> 
  <tr> 
   <td align="center">虚拟IP</td> 
   <td align="right">-</td> 
   <td align="right">192.168.126.200</td> 
  </tr> 
 </tbody> 
</table>

--------------------

# 官网 #

[https://keepalived.readthedocs.io/en/latest/\#][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][CentOS 7 yum_ 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.loc
            failover@firewall.loc
            sysadmin@firewall.loc
       }
    
        notification_email_from example@example.com
        smtp_server mail.example.com
        smtp_connect_timeout 30
        router_id LVS_DEVEL
    }
    vrrp_script chk_tomcat { 
        script "/etc/keepalived/tomcat_check.sh"
        interval 5
        weight -5
        fall 3  
        rise 2
    }
    vrrp_instance VI_1 { 
        state MASTER
        interface ens33
        mcast_src_ip 192.168.126.137
        virtual_router_id 51
        priority 101
        advert_int 2
        authentication { 
            auth_type PASS
            auth_pass 1111
        }
        virtual_ipaddress { 
            192.168.126.200
        }
        track_script { 
           chk_tomcat
        }
    }

--------------------

## 138 ##

! Configuration File for keepalived
    global_defs { 
        notification_email { 
    	acassen@firewall.loc
            failover@firewall.loc
            sysadmin@firewall.loc
       }
    
        notification_email_from example@example.com
        smtp_server mail.example.com
        smtp_connect_timeout 30
        router_id LVS_DEVEL
    }
    vrrp_script chk_tomcat { 
        script "/etc/keepalived/tomcat_check.sh"
        interval 5
        weight -5
        fall 3  
        rise 2
    }
    vrrp_instance VI_1 { 
        state BACKUP
        interface ens33
        mcast_src_ip 192.168.126.138
        virtual_router_id 51
        priority 99
        advert_int 2
        authentication { 
            auth_type PASS
            auth_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 ];then
    	echo "tomcat is stop"
    	sleep 2
    	if [ `ps -C java --no-heading| wc -l` -eq 0 ];then
    		systemctl 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][https_keepalived.readthedocs.io_en_latest_configuration_synopsis.html]

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70]

! Configuration File for keepalived
    global_defs { 
        notification_email { 
    	acassen@firewall.loc
            failover@firewall.loc
            sysadmin@firewall.loc
       }
    
        notification_email_from example@example.com
        smtp_server mail.example.com
        smtp_connect_timeout 30
        router_id LVS_DEVEL
    }
    
    
    
    vrrp_script chk_tomcat { 
        script "/etc/keepalived/tomcat_check.sh"
        interval 5
        weight -5
        fall 3  
        rise 2
    }
    vrrp_instance VI_1 { 
        state MASTER
        interface ens33
        mcast_src_ip 192.168.126.137
        virtual_router_id 51
        priority 101
        advert_int 2
        authentication { 
            auth_type PASS
            auth_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

--------------------

![在这里插入图片描述][20201230010515137.gif_pic_center]

[https_keepalived.readthedocs.io_en_latest]: https://keepalived.readthedocs.io/en/latest/#
[CentOS 7 yum_ Tomcat]: https://blog.csdn.net/github_38336924/article/details/82253553
[https_keepalived.readthedocs.io_en_latest_configuration_synopsis.html]: https://keepalived.readthedocs.io/en/latest/configuration_synopsis.html
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70]: /images/20221120/17defb6327b44fd9a09e03686325220b.png
[20201230010515137.gif_pic_center]: /images/20221120/1b8fcab85d5244b6942a00257320b055.png