Keepalived案例一:Keepalived雙機熱備(HA)精講
一,Keepalived雙機熱備的應用場景
1,網站流量不高,壓力不大,但是對伺服器的可靠性要求極其高,例如實時線上OA系統,政府部門網站系統,醫院實時報醫系統,公安局線上報案系統,股市後臺網站系統等等,他們的壓力不是很大,但是對可靠性要求是非常高的
2,有錢沒地方花的,典型的政府企業,公辦學校等等
二,Keepalived雙機熱備的特性以及優缺點
特性:
1,至少需要兩臺伺服器,其中一臺為master始終提供服務,另外一臺作為backup始終處於空閒狀態,只有在主伺服器掛掉的時候他就來幫忙了,這是典型的雙擊熱備
2,能根據需求判斷服務是否可用,在不可用的時候要即使切換
優缺點:
優點:資料同步非常簡單,不像負載均衡對資料一致性要求非常高,實現起來相對複雜維護也頗為不便,雙機熱備用rsync就可以實現了操作和維護非常簡單
缺點:伺服器有點浪費,始終有一臺處於空閒狀態
三,Keepalived雙機熱備的配置
首先畫個雙機熱備拓撲圖吧:
這裡我只寫最終實現的配置,至於Keepalived的理論知識請參考《Keepalived原理與實戰精講》
1,本例通過Keepalived來實現兩臺LNMP(也就是linux+nginx+mysql+php)架構伺服器的雙機熱備
LNMP的配置請參考:《Lnmp配置精講第一版》
2,Keepalived配置雙機安裝配置
1》Keepalived安裝
keepalived官方地址:http://www.keepalived.org/download.html,大家可以到這裡下載最新版本的keepalived
作業系統:centos 5.5 32bit
系統安裝:最小化安裝,也就是去掉所有元件
環境配置:安裝make 和 gcc openssl openssl-devel等等
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yum -y install gcc make openssl openssl-devel wget kernel-devel
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mkdir -p /usr/local/src/hasoft
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cd /usr/local/src/hasoft
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wget http://www.keepalived.org/software/keepalived-1.2.2.tar.gz
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tar -zxvf keepalived-1.2.2.tar.gz
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cd keepalived-1.2.2
- ./configure --prefix=/usr/local/keepalived --with-kernel-dir=/usr/src/kernels/2.6.18-238.19.1.el5-i686/
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Keepalived configuration
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------------------------
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Keepalived version : 1.2.2
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Compiler : gcc
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Compiler flags : -g -O2 -DETHERTYPE_IPV6=0x86dd
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Extra Lib : -lpopt -lssl -lcrypto
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Use IPVS Framework : Yes
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IPVS sync daemon support : Yes
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IPVS use libnl : No
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Use VRRP Framework : Yes
- Use Debug flags : No
- make && make install
./configure --prefix=/usr/local/keepalived --with-kernel-dir=/usr/src/kernels/2.6.18-238.19.1.el5-i686/ --disable-lvs-syncd --disable-lvs
但這個沒有影響,就按照我的來配置吧,不過如果你要是集成了LVS,那麼就不可加這兩個引數了哦
整理管理檔案:
cp /usr/local/keepalived/sbin/keepalived /usr/sbin/
cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/
建立配置檔案目錄(注意:keepalived的配置檔案預設在/etc/keepalived/目錄)
mkdir -p /etc/etc/keepalived/
兩臺伺服器(兩個節點)都這樣安裝即可
2》配置
節點A配置如下:
vi /etc/keepalived/keepalived.conf
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global_defs
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{
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notification_email
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{
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[email protected]
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[email protected]
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}
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notification_email_from [email protected]
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smtp_server 127.0.0.1
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stmp_connect_timeout 30
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router_id lnmp_node1
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}
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vrrp_instance lnmp {
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state MASTER
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interface eth0
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virtual_router_id 100
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priority 200
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advert_int 5
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track_interface {
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eth0
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eth1
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}
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authentication {
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auth_type PASS
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auth_pass 123456
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}
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virtual_ipaddress {
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192.168.17.200
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}
- }
節點B配置如下:
vi /etc/keepalived/keepalived.conf
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global_defs
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{
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notification_email
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{
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[email protected]
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[email protected]
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}
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notification_email_from [email protected]
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smtp_server 127.0.0.1
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stmp_connect_timeout 30
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router_id lnmp_node1
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}
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vrrp_instance lnmp {
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state MASTER
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interface eth0
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virtual_router_id 100
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priority 150
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advert_int 5
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track_interface {
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eth0
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eth1
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}
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authentication {
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auth_type PASS
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auth_pass 123456
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}
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virtual_ipaddress {
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192.168.17.200
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}
- }
在節點A上啟動
/usr/local/keepalived/sbin/keepalived
啟動日誌:
Sep 8 18:26:02 centosa Keepalived_vrrp: Registering Kernel netlink reflector
Sep 8 18:26:02 centosa Keepalived_vrrp: Registering Kernel netlink command channel
Sep 8 18:26:02 centosa Keepalived_vrrp: Registering gratutious ARP shared channel
Sep 8 18:26:02 centosa Keepalived_vrrp: Opening file '/etc/keepalived/keepalived.conf'.
Sep 8 18:26:02 centosa Keepalived_vrrp: Configuration is using : 36076 Bytes
Sep 8 18:26:02 centosa Keepalived_vrrp: Using LinkWatch kernel netlink reflector...
Sep 8 18:26:02 centosa Keepalived: Starting VRRP child process, pid=5606
Sep 8 18:26:07 centosa Keepalived_vrrp: VRRP_Instance(lnmp) Transition to MASTER STATE
Sep 8 18:26:12 centosa Keepalived_vrrp: VRRP_Instance(lnmp) Entering MASTER STATE
Sep 8 18:26:12 centosa avahi-daemon[2528]: Registering new address record for 192.168.17.200 on eth0.
在節點B上啟動
/usr/local/keepalived/sbin/keepalived
開機自動啟動
echo /usr/local/keepalived/sbin/keepalived >> /etc/rc.local
啟動日誌:
Sep 8 18:30:02 centosb Keepalived: Starting Keepalived v1.2.2 (09/08,2011)
Sep 8 18:30:02 centosb Keepalived: Starting Healthcheck child process, pid=5837
Sep 8 18:30:02 centosb Keepalived_vrrp: Registering Kernel netlink reflector
Sep 8 18:30:02 centosb Keepalived_vrrp: Registering Kernel netlink command channel
Sep 8 18:30:02 centosb Keepalived_vrrp: Registering gratutious ARP shared channel
Sep 8 18:30:02 centosb Keepalived: Starting VRRP child process, pid=5839
Sep 8 18:30:02 centosb kernel: IPVS: Registered protocols (TCP, UDP, AH, ESP)
Sep 8 18:30:02 centosb kernel: IPVS: Connection hash table configured (size=4096, memory=32Kbytes)
Sep 8 18:30:02 centosb kernel: IPVS: ipvs loaded.
Sep 8 18:30:02 centosb Keepalived_healthcheckers: Registering Kernel netlink reflector
Sep 8 18:30:02 centosb Keepalived_healthcheckers: Registering Kernel netlink command channel
Sep 8 18:30:02 centosb Keepalived_healthcheckers: Opening file '/etc/keepalived/keepalived.conf'.
Sep 8 18:30:02 centosb Keepalived_vrrp: Opening file '/etc/keepalived/keepalived.conf'.
Sep 8 18:30:02 centosb Keepalived_vrrp: Configuration is using : 36252 Bytes
Sep 8 18:30:02 centosb Keepalived_vrrp: Using LinkWatch kernel netlink reflector...
Sep 8 18:30:02 centosb Keepalived_healthcheckers: Configuration is using : 6271 Bytes
Sep 8 18:30:02 centosb Keepalived_healthcheckers: Using LinkWatch kernel netlink reflector...
Sep 8 18:30:02 centosb Keepalived_vrrp: VRRP_Instance(lnmp) Entering BACKUP STATE
從日誌可以看出,啟動都沒有問題,並且安裝我給的優先順序完成了競選,各自成就了各自的狀態
關閉節點A的網絡卡測試切換是否正常
ifdown eth0
觀察節點B的日誌:
Sep 8 18:32:55 centosb Keepalived_vrrp: VRRP_Instance(lnmp) Transition to MASTER STATE
Sep 8 18:33:00 centosb Keepalived_vrrp: VRRP_Instance(lnmp) Entering MASTER STATE
Sep 8 18:33:00 centosb avahi-daemon[2531]: Registering new address record for 192.168.17.200 on eth0.
啟動節點A的網絡卡測試切換是否正常
ifup eth0
觀察節點B的日誌:
Sep 8 18:33:31 centosb Keepalived_vrrp: VRRP_Instance(lnmp) Received higher prio advert
Sep 8 18:33:31 centosb Keepalived_vrrp: VRRP_Instance(lnmp) Entering BACKUP STATE
Sep 8 18:33:31 centosb avahi-daemon[2531]: Withdrawing address record for 192.168.17.200 on eth0.
Received higher prio advert:表示接收到更高優先順序的公告(advert公告的意思)
Withdrawing:撤回的意思,可以看出切換過程一目瞭然
OK,到這裡我們的安裝部分完成,下面我們來看看如何監控服務吧,我們這裡僅僅是監控了網路故障和keepalived本身程序,在網路或者keepalived程序出現問題的時候會切換,但是我的節點A裡面還有很多服務呢,例如nginx,PHP,mysql程序出問題或高負載的時候相應過慢怎麼辦,怎麼切換的呢,這時就要用到指令碼了,下面我們來看看keepalived是如何控制指令碼來實現對伺服器的監控和切換的
寫個指令碼來實時監控三個服務,若有一個出現問題遍切換mkdir /root/shell/
cd /root/shell
vi keepcheck.sh
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#!/bin/bash
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while :
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do
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mysqlcheck=`/usr/local/lnmp/mysql/bin/mysqladmin -uroot ping 2>&1`
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mysqlcode=`echo $?`
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phpcheck=`ps -C php-fpm --no-header | wc -l`
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nginxcheck=`ps -C nginx --no-header | wc -l`
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keepalivedcheck=`ps -C keepalived --no-header | wc -l`
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if [ $nginxcheck -eq 0 ]|| [ $phpcheck -eq 0 ]||[ $mysqlcode -ne 0 ];then
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if [ $keepalivedcheck -ne 0 ];then
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killall -TERM keepalived
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else
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echo "keepalived is stoped"
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fi
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else
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if [ $keepalivedcheck -eq 0 ];then
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/etc/init.d/keepalived start
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else
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echo "keepalived is running"
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fi
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fi
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sleep 5
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done
啟動指令碼:
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chmod +x /root/shell/keepcheck.sh
- nohup sh /root/shell/keepcheck.sh &
寫入/etc/rc.local開機自動啟動
- echo "nohup sh /root/shell/keepcheck.sh &" >> /etc/rc.loal
可以測試了
開了防火牆之後雙節點都變成master了,日誌如下
Sep 13 21:21:27 centosb avahi-daemon[2528]: Withdrawing address record for fe80::20c:29ff:fede:99ab on eth1.
Sep 13 21:21:27 centosb avahi-daemon[2528]: Withdrawing address record for 192.168.27.212 on eth1.
Sep 13 21:21:27 centosb avahi-daemon[2528]: Withdrawing address record for fe80::20c:29ff:fede:99a1 on eth0.
Sep 13 21:21:27 centosb avahi-daemon[2528]: Withdrawing address record for 192.168.17.212 on eth0.
Sep 13 21:21:27 centosb avahi-daemon[2528]: Host name conflict, retrying with <centosb-48>
Sep 13 21:21:27 centosb avahi-daemon[2528]: Registering new address record for fe80::20c:29ff:fede:99ab on eth1.
Sep 13 21:21:27 centosb avahi-daemon[2528]: Registering new address record for 192.168.27.212 on eth1.
Sep 13 21:21:27 centosb avahi-daemon[2528]: Registering new address record for fe80::20c:29ff:fede:99a1 on eth0.
Sep 13 21:21:27 centosb avahi-daemon[2528]: Registering new address record for 192.168.17.200 on eth0.
Sep 13 21:21:27 centosb avahi-daemon[2528]: Registering new address record for 192.168.17.212 on eth0.
解決方法如下:(一般使用第二種情況)
第一種情況,如果用的是預設防火牆
只需要新增:iptables -I RH-Firewall-1-INPUT -d 224.0.0.18 -j ACCEPT
第二種情況:如果是自己用指令碼設定的防火牆,只需要新增西門規則即可iptables
-A OUTPUT -o eth0-d
224.0.0.18 -j ACCEPT
iptables -A OUTPUT -o eth0 -s 224.0.0.18 -j ACCEPT
iptables
-A INPUT -i eth0-d
224.0.0.18 -j ACCEPT
iptables -A INPUT -i eth0 -s 224.0.0.18 -j ACCEPT
修改完後,記得使用/etc/rc.d/init.d/iptables save 儲存修改的規則,並會將規則寫入/etc/sysconfig/iptables檔案中去,否則重啟後會失效。
在/etc/sysconfig/iptables檔案中,要將INPUT鏈和OUTPUT鏈中的REJECT規則放到最後,否則會影響上面設定的功能。
最後,使用service iptables restart ,重啟iptables使規則生效。
轉自 http://bbs.nanjimao.com/thread-855-1-1.html