使用KeepAlived實現主備服務

使用KeepAlived實現主備服務

使用兩臺機器 + 一個虛擬IP

兩臺機器上分別啓動着本身的HTTP服務，端口8999。

安裝KeepAlived

在兩臺機器上安裝keepalived

yum install keepalived -y

配置keepAlived

在master那臺，配置文件位於/etc/keepalived/keepalived.conf

寫入內容

global_defs {
   router_id ljktest 
}

vrrp_script chk_http_port {
        script "</dev/tcp/127.0.0.1/8999"
        interval 1
        weight 2
}

vrrp_instance VI_1 {
    state MASTER
    interface ens32
    virtual_router_id 51
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        192.168.0.131
    }
    track_script {
        chk_http_port  
    }
}

在Backup那臺寫入

global_defs {
   router_id ljktest 
}

vrrp_script chk_http_port {
        script "</dev/tcp/127.0.0.1/8999"
        interval 1
        weight 2
}

vrrp_instance VI_1 {
    state MASTER
    interface ens32
    virtual_router_id 51
    priority 99
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        192.168.0.131
    }
    track_script {
        chk_http_port  
    }
}

兩臺的配置，只有priority的值不同。且要配置成MASTER的那臺必須大於BACKUP那臺。

啓動keepAlived

systemctl start keepalived

在Master那臺可以看到，網卡上面多了一條這樣的信息。證實生效了。訪問服務192.168.0.131:8999下的服務，會定向到Master那臺上面。

inet 192.168.0.131/32 scope global ens32
valid_lft forever preferred_lft forever

測試

關閉KeepAlived，主備切換

關閉Master這臺的keepalived，發現BACKUP這臺變成主。

重啓Master這臺的keepalived，發現Master這臺又會成爲主。

關閉應用程序，主備切換

目前這樣的配置，關閉應用程序沒法進行主備切換。

不明白爲何</dev/tcp/127.0.0.1/8999 不會生效。

本身寫個腳原本檢測試試

xypt_logs_check.sh

#!/bin/bash
count=`ps -ef|grep xypt_logs_producer|grep -v grep|wc -l`
if [ $count -gt 0 ];then
    exit 0
else
    exit 1
fi

腳本做用就是用來查看下這個應用進程是否存在，不存在異常退出，存在則正常退出。

配置腳本部分修改爲

vrrp_script chk_http_port {
        script "/etc/keepalived/xypt_logs_check.sh"
        interval 2
        weight 2
        fall 3
        rise 2
}

接下來咱們關閉Master這臺上的應用，VIP地址會漂移到Backup那臺。再啓動回來，VIP地址又會再漂移到Master這臺。

查看Master這臺/var/log/messages日誌，能夠看到它的遷移過程。

Aug  7 12:57:17 nn1 Keepalived_vrrp[4088]: /etc/keepalived/xypt_logs_check.sh exited with status 1
Aug  7 12:57:19 nn1 Keepalived_vrrp[4088]: /etc/keepalived/xypt_logs_check.sh exited with status 1
Aug  7 12:57:21 nn1 Keepalived_vrrp[4088]: /etc/keepalived/xypt_logs_check.sh exited with status 1
Aug  7 12:57:21 nn1 Keepalived_vrrp[4088]: VRRP_Script(chk_http_port) failed
Aug  7 12:57:22 nn1 Keepalived_vrrp[4088]: VRRP_Instance(VI_1) Changing effective priority from 102 to 100
Aug  7 12:57:23 nn1 Keepalived_vrrp[4088]: VRRP_Instance(VI_1) Received advert with higher priority 101, ours 100
Aug  7 12:57:23 nn1 Keepalived_vrrp[4088]: VRRP_Instance(VI_1) Entering BACKUP STATE
Aug  7 12:57:23 nn1 Keepalived_vrrp[4088]: VRRP_Instance(VI_1) removing protocol VIPs.


Aug  7 12:57:49 nn1 Keepalived_vrrp[4088]: /etc/keepalived/xypt_logs_check.sh exited with status 1
Aug  7 12:57:51 nn1 Keepalived_vrrp[4088]: /etc/keepalived/xypt_logs_check.sh exited with status 1
Aug  7 12:57:55 nn1 Keepalived_vrrp[4088]: VRRP_Script(chk_http_port) succeeded
Aug  7 12:57:56 nn1 Keepalived_vrrp[4088]: VRRP_Instance(VI_1) Changing effective priority from 100 to 102
Aug  7 12:57:57 nn1 Keepalived_vrrp[4088]: VRRP_Instance(VI_1) forcing a new MASTER election
Aug  7 12:57:58 nn1 Keepalived_vrrp[4088]: VRRP_Instance(VI_1) Transition to MASTER STATE
Aug  7 12:57:59 nn1 Keepalived_vrrp[4088]: VRRP_Instance(VI_1) Entering MASTER STATE
Aug  7 12:57:59 nn1 Keepalived_vrrp[4088]: VRRP_Instance(VI_1) setting protocol VIPs.
Aug  7 12:57:59 nn1 Keepalived_vrrp[4088]: Sending gratuitous ARP on ens32 for 192.168.0.131
Aug  7 12:57:59 nn1 Keepalived_vrrp[4088]: VRRP_Instance(VI_1) Sending/queueing gratuitous ARPs on ens32 for 192.168.0.131
Aug  7 12:57:59 nn1 Keepalived_vrrp[4088]: Sending gratuitous ARP on ens32 for 192.168.0.131

總結

1. keepalived的主備狀態與state值設置無關；
2. 主備機由priority值和vrrp_script中的weight值之和決定，大的爲主；
3. 主備比較權值=priority值+weight值*標誌位，當vrrp_script檢測腳本爲true時標誌位爲1，反之爲0；
4. 爲保證正常的主備切換，weight值應大於主備priority值之差。

附錄

• KeepAlived實現主備以及原理
• 監聽端口並實現熱備
• keepalive + nginx場景測試