文章目錄

• Pre
• 環境信息
• 官網
• 原理
• keepalived 安裝
• • 137 安裝 keepalived
  • 138 安裝 keepalived
• 配置keepalived的配置文件/etc/keepalived/keepalived.conf
• • 關鍵參數解讀
  • 137
  • 138
• 檢測腳本
• 日志
• 狀態發生變更，觸發腳本
• 小結
• Questions
• • exited due to signal 15
  • notify_master notify_backup未生效

Pre

雙機熱備是指兩臺機器都在運行，但并不是兩臺機器都同時在提供服務。

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環境信息

節點軟件IP

節點A	keepalived + tomcat	192.168.126.137
節點B	keepalived + tomcat	192.168.126.138
虛擬IP	-	192.168.126.200

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官網

https://keepalived.readthedocs.io/en/latest/#

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原理

keepalived用于保證環境高可用，防止單點故障。

keepalived主要有三個模塊，分別是core、check和VRRP。

• core核心模塊，負責主進程的啟動、維護以及全局配置文件的加載和解析
• check負責健康檢查，包括常見的各種檢查方式
• VRRP模塊實現VRRP協議

VRRP（Virtual Router Redundancy Protocol） 即虛擬路由冗余協議，實現路由器高可用的協議，即將N臺提供相同功能的路由器組成一個路由器組，這個組里面有一個master和多個backup，master上面有一個對外提供服務的vip（該路由器所在局域網內其他機器的默認路由為該vip），master會發組播，當backup收不到VRRP包時就認為master宕掉了，這時就需要根據VRRP的優先級來選舉一個backup當master。這樣的話就可以保證路由器的高可用了。

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keepalived 安裝

兩個節點均需要安裝， 在137 和 138 節點上安裝 ，執行 yum install keepalived

137 安裝 keepalived

[root@localhost ~]# yum install keepalived Loaded plugins: fastestmirror ....... ....... Complete! [root@localhost ~]#

138 安裝 keepalived

[root@localhost ~]# yum install keepalived Loaded plugins: fastestmirror ....... ....... Complete! [root@localhost ~]#

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tomcat 也都裝下哈 ，用于驗證，可以yum安裝

CentOS 7 yum安裝與配置 Tomcat 寫的挺不錯，沒有的話可以參考

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配置keepalived的配置文件/etc/keepalived/keepalived.conf

關鍵參數解讀

state 主服務器為MASTER，其他服務器均為BACKUP interface 通信用的網卡，ip addr可以查看，以實際為準 virtual_router_id 主從服務器此ID必須一致 priority 優先級，主服務器必須大于其他服務器，數值越大優先級越高 authentication 主從服務器必須一致 virtual_ipaddress 虛擬IP地址，主從服務器必須一致，該VIP為客戶端訪問時使用的IP

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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} }

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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} }

與主節點的配置上的區別，需要注意

state 表示一個是主機一個是備機，mcast_src_ip 當前服務器的ip，priority 主機要比備機的要高

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檢測腳本

!/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

比較簡單，根據實際情況調整

檢測是否有tomcat在運行，如果沒有的話，等2秒，如果還沒有就把keepalived給停止掉，這樣vip就能從主機master切換到備機BACKUP上了。

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日志

可以查看 /var/log/messages 日志 觀察切換和選主的過程。

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狀態發生變更，觸發腳本

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

當節點從BACKUP 轉為 MASTER的時候 ，執行 /etc/keepalived/a.sh

當節點從MASTER 轉為 BACKUP的時候 ，執行 /etc/keepalived/b.sh

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小結

MASTER和 BACKUP，預先分配好， 通過priority 來確定， 當MASTER宕機以后，BACKUP 沒有收到 MASTER的 VRRP消息，BACKUP就認為 MASTER宕機了，這個時候就把自己選舉為MASTER。

MASTER宕機，本節點的日志

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節點的日志

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.

當MASTER恢復以后，MASTER發送VRRP消息給BACKUP，這個時候雖然BACKUP是MASTER，但是 比較Prority后，發現自己的Prority小，會進入BACKUP模式，這個時候，之前設置的MASTER就又變成了MASTER了 。

MASTER恢復，本節點的日志

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節點的日志

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.

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Questions

exited due to signal 15

/var/log/messages 日志提示：/etc/keepalived/check_nginx.sh exited due to signal 15

調整如下參數

interval 5 #監控腳本的執行時間要大于advert_int advert_int 2 #心跳檢查間隔時間

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notify_master notify_backup未生效

檢查 getenforce

getenforce 如果 開啟的話，關閉 執行 setenforce 0

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總結

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