keepalived的部署
keepalived在很多高可用的集羣都會用到，一般前端放置的會是nginx、ipvs、haproxy
比如我們在使用rabbitmq的時候做了這麼一個集羣，一般做了集羣的話，那肯定就需要這麼一個高可用的負載均衡器來實現流量的分發，如果使用的是haproxy,比如一臺rebbitmq的節點突然宕機或者網卡失效，那麼雖然RabbitMQ集羣沒有任何故障，但是對於外界的客戶端來說所有的連接都會被斷開，結果將是災難性的。確保負載均衡服務的可靠性同樣顯得十分的重要。這裏就引入Keepalived工具，它能夠通過自身健康檢查、資源接管功能做高可用（雙機熱備），實現故障轉移。
Keepalived採用VRRP（Virtual Router Redundancy Protocol，虛擬路由冗餘協議），以軟件的形式實現服務器熱備功能。通常情況下是將兩臺Linux服務器組成一個熱備組（Master和Backup），同一時間熱備組內只有一臺主服務器Master提供服務，同時Master會虛擬出一個公用的虛擬IP地址，簡稱VIP。這個VIP只存在在Master上並對外提供服務。如果Keepalived檢測到Master宕機或者服務故障，備份服務器Backup會自動接管VIP稱爲Master，Keepalived並將原Master從熱備組中移除。當原Master恢復後，會自動加入到熱備組，默認再搶佔稱爲Master，起到故障轉移的功能。
Keepalived工作在OSI模型中的第3層、第4層和第7層。
工作在第3層是指Keepalived會定期向熱備組中的服務器發送一個ICMP數據包來判斷某臺服務器是否故障，如果故障則將這臺服務器從熱備組移除。
工作在第4層是指Keepalived以TCP端口的狀態判斷服務器是否故障，比如檢測RabbitMQ的5672端口，如果故障則將這臺服務器從熱備組中移除。
工作在第7層是指Keepalived根據用戶設定的策略（通常是一個自定義的檢測腳本）判斷服務器上的程序是否正常運行，如果故障將這臺服務器從熱備組移除。
首先需要去Keepalived的官網下載Keepalived的安裝文件，目前最新的版本爲：keepalived-2.0.20.tar.gz，下載地址爲http://www.keepalived.org/download.html
可以找到最新版
[root@VM_0_8_centos ~]# mkdir keepalived
[root@VM_0_8_centos ~]# cd keepalived/
[root@VM_0_8_centos keepalived]# wget https://www.keepalived.org/software/keepalived-2.0.20.tar.gz
--2020-02-27 10:46:37-- https://www.keepalived.org/software/keepalived-2.0.20.tar.gz
Resolving www.keepalived.org (www.keepalived.org)... 37.59.63.157, 2001:41d0:8:7a9d::1
Connecting to www.keepalived.org (www.keepalived.org)|37.59.63.157|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 1036063 (1012K) [application/x-gzip]
Saving to: ‘keepalived-2.0.20.tar.gz’
100%[==================================================================================================================================>] 1,036,063 13.7KB/s in 1m 43s
2020-02-27 10:48:37 (9.80 KB/s) - ‘keepalived-2.0.20.tar.gz’ saved [1036063/1036063]解壓
[root@VM_0_8_centos keepalived]# ls
keepalived-2.0.20.tar.gz
[root@VM_0_8_centos keepalived]# tar xf keepalived-2.0.20.tar.gz
[root@VM_0_8_centos keepalived]# cd keepalived-2.0.20/
[root@VM_0_8_centos keepalived-2.0.20]# ls
aclocal.m4 AUTHOR build_setup compile configure.ac COPYING doc INSTALL keepalived lib Makefile.in README.md TODO
ar-lib bin_install ChangeLog configure CONTRIBUTORS depcomp genhash install-sh keepalived.spec.in Makefile.am missing snap
[root@VM_0_8_centos keepalived-2.0.20]# ./configure --prefix=/opt/keepalived --with-init=SYSV
checking for a BSD-compatible install... /usr/bin/install -c
checking whether build environment is sane... yes
checking for a thread-safe mkdir -p... /usr/bin/mkdir -p
checking for gawk... gawk
checking whether make sets $(MAKE)... yes
checking whether make supports nested variables... yes
checking whether make supports nested variables... (cached) yes
checking for pkg-config... /usr/bin/pkg-config
checking pkg-config is at least version 0.9.0... yes
checking for gcc... gcc
checking whether the C compiler works... yes
checking for C compiler default output file name... a.out出現報錯：缺少openssl-devel
configure: error:
!!! OpenSSL is not properly installed on your system. !!!
!!! Can not include OpenSSL headers files. !!!
[root@VM_0_8_centos keepalived-2.0.20]# yum -y install openssl-devel
Loaded plugins: fastestmirror, langpacks
Determining fastest mirrors
Resolving Dependencies
--> Running transaction check
---> Package openssl-devel.x86_64 1:1.0.2k-19.el7 will be installed安裝後重新再執行[root@VM_0_8_centos keepalived-2.0.20]# ./configure --prefix=/opt/keepalived --with-init=SYSV
再次報錯，說這個版本不支持ipv6，需要安裝依賴包
*** WARNING - this build will not support IPVS with IPv6. Please install libnl/libnl-3 dev libraries to support IPv6 with IPVS.
[root@VM_0_8_centos keepalived-2.0.20]# yum -y install libnl libnl-devel
Loaded plugins: fastestmirror, langpacks
Loading mirror speeds from cached hostfile
Package libnl-1.1.4-3.el7.x86_64 already installed and latest version安裝完依賴包再次執行
[root@VM_0_8_centos keepalived-2.0.20]# ./configure --prefix=/opt/keepalived --with-init=SYSV 編譯
[root@VM_0_8_centos keepalived-2.0.20]# make && make install將啓動文件放到/etc/init.d下，可以使用service來啓動keepalived
[root@VM_0_8_centos keepalived-2.0.20]# cp /opt/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/
[root@VM_0_8_centos keepalived-2.0.20]# cp /opt/keepalived/etc/sysconfig/keepalived /etc/sysconfig
[root@VM_0_8_centos keepalived-2.0.20]# cp /opt/keepalived/sbin/keepalived /usr/sbin
[root@VM_0_8_centos keepalived-2.0.20]# chmod +x /etc/init.d/keepalived
[root@VM_0_8_centos keepalived-2.0.20]# chkconfig --add keepalived
[root@VM_0_8_centos keepalived-2.0.20]# chkconfig keepalived on
[root@VM_0_8_centos keepalived-2.0.20]# cp /opt/keepalived/etc/keepalived/keepalived.conf /etc/keepalived.conf啓動失敗，查看報錯，這裏提示 Unable to find configuration file /etc/keepalived/keepalived.conf，沒有發現我們的配置文件的地址，這裏是因爲我們在安裝的時候指定了自己的安裝路徑
[root@VM_0_8_centos keepalived-2.0.20]# service keepalived start
Starting keepalived (via systemctl): Job for keepalived.service failed because the control process exited with error code. See "systemctl status keepalived.service" and "journalctl -xe" for details.
[FAILED]
[root@VM_0_8_centos keepalived-2.0.20]# journalctl -xe
找出放置我們配置文件的地方，修改文件地址
[root@VM_0_8_centos ~]# find / -name keepalived.conf
/opt/keepalived/etc/keepalived/keepalived.conf
/etc/keepalived.conf
/root/keepalived/keepalived-2.0.20/keepalived/etc/keepalived/keepalived.conf在最後一行添加我們配置文件的地址
[root@VM_0_8_centos ~]# vim /etc/sysconfig/keepalived
[root@VM_0_8_centos ~]# tail -1 /etc/sysconfig/keepalived
KEEPALIVED_OPTIONS="-f /etc/keepalived.conf -D -S 0"使用systemctl啓動成功
[root@VM_0_8_centos ~]# systemctl restart keepalived
[root@VM_0_8_centos ~]# systemctl status keepalived
● keepalived.service - SYSV: Start and stop Keepalived
Loaded: loaded (/etc/rc.d/init.d/keepalived; bad; vendor preset: disabled)
Active: active (running) since Thu 2020-02-27 11:02:22 CST; 10s ago
Docs: man:systemd-sysv-generator(8)
Process: 30129 ExecStart=/etc/rc.d/init.d/keepalived start (code=exited, status=0/SUCCESS)
Main PID: 30136 (keepalived)
CGroup: /system.slice/keepalived.service
├─30136 keepalived -f /etc/keepalived.conf -D -S 0
├─30138 keepalived -f /etc/keepalived.conf -D -S 0
└─30139 keepalived -f /etc/keepalived.conf -D -S 0
Feb 27 11:02:31 VM_0_8_centos Keepalived_vrrp[30139]: Sending gratuitous ARP on eth0 for 192.168.200.18
Feb 27 11:02:31 VM_0_8_centos Keepalived_vrrp[30139]: Sending gratuitous ARP on eth0 for 192.168.200.16
Feb 27 11:02:31 VM_0_8_centos Keepalived_vrrp[30139]: Sending gratuitous ARP on eth0 for 192.168.200.17
Feb 27 11:02:31 VM_0_8_centos Keepalived_vrrp[30139]: Sending gratuitous ARP on eth0 for 192.168.200.18
Feb 27 11:02:31 VM_0_8_centos Keepalived_healthcheckers[30138]: HTTP_CHECK on service [192.168.200.3]:tcp:1358 failed after 3 retry.
Feb 27 11:02:31 VM_0_8_centos Keepalived_healthcheckers[30138]: Removing service [192.168.200.3]:tcp:1358 to VS [10.10.10.2]:tcp:1358
Feb 27 11:02:31 VM_0_8_centos Keepalived_healthcheckers[30138]: Lost quorum 1-0=1 > 0 for VS [10.10.10.2]:tcp:1358
Feb 27 11:02:31 VM_0_8_centos Keepalived_healthcheckers[30138]: Adding sorry server [192.168.200.200]:tcp:1358 to VS [10.10.10.2]:tcp:1358
Feb 27 11:02:31 VM_0_8_centos Keepalived_healthcheckers[30138]: Removing alive servers from the pool for VS [10.10.10.2]:tcp:1358
Feb 27 11:02:31 VM_0_8_centos Keepalived_healthcheckers[30138]: Remote SMTP server [192.168.200.1]:25 connected.使用service進行啓動停止
[root@VM_0_8_centos ~]# service keepalived stop
Stopping keepalived (via systemctl): [ OK ]
[root@VM_0_8_centos ~]# service keepalived start
Starting keepalived (via systemctl): [ OK ]
[root@VM_0_8_centos ~]# service keepalived status
● keepalived.service - SYSV: Start and stop Keepalived
Loaded: loaded (/etc/rc.d/init.d/keepalived; bad; vendor preset: disabled)
Active: active (running) since Thu 2020-02-27 11:03:27 CST; 10s ago
Docs: man:systemd-sysv-generator(8)
Process: 30394 ExecStop=/etc/rc.d/init.d/keepalived stop (code=exited, status=0/SUCCESS)
Process: 30469 ExecStart=/etc/rc.d/init.d/keepalived start (code=exited, status=0/SUCCESS)
Main PID: 30476 (keepalived)
CGroup: /system.slice/keepalived.service
├─30476 keepalived -f /etc/keepalived.conf -D -S 0
├─30478 keepalived -f /etc/keepalived.conf -D -S 0
└─30479 keepalived -f /etc/keepalived.conf -D -S 0
Feb 27 11:03:36 VM_0_8_centos Keepalived_vrrp[30479]: Sending gratuitous ARP on eth0 for 192.168.200.18
Feb 27 11:03:36 VM_0_8_centos Keepalived_vrrp[30479]: Sending gratuitous ARP on eth0 for 192.168.200.16
Feb 27 11:03:36 VM_0_8_centos Keepalived_vrrp[30479]: Sending gratuitous ARP on eth0 for 192.168.200.17
Feb 27 11:03:36 VM_0_8_centos Keepalived_vrrp[30479]: Sending gratuitous ARP on eth0 for 192.168.200.18
Feb 27 11:03:37 VM_0_8_centos Keepalived_healthcheckers[30478]: HTTP_CHECK on service [192.168.200.3]:tcp:1358 failed after 3 retry.
Feb 27 11:03:37 VM_0_8_centos Keepalived_healthcheckers[30478]: Removing service [192.168.200.3]:tcp:1358 to VS [10.10.10.2]:tcp:1358
Feb 27 11:03:37 VM_0_8_centos Keepalived_healthcheckers[30478]: Lost quorum 1-0=1 > 0 for VS [10.10.10.2]:tcp:1358
Feb 27 11:03:37 VM_0_8_centos Keepalived_healthcheckers[30478]: Adding sorry server [192.168.200.200]:tcp:1358 to VS [10.10.10.2]:tcp:1358
Feb 27 11:03:37 VM_0_8_centos Keepalived_healthcheckers[30478]: Removing alive servers from the pool for VS [10.10.10.2]:tcp:1358
Feb 27 11:03:37 VM_0_8_centos Keepalived_healthcheckers[30478]: Remote SMTP server [192.168.200.1]:25 connected.