keepalived的部署
keepalived在很多高可用的集群都会用到，一般前端放置的会是nginx、ipvs、haproxy

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比如我们在使用rabbitmq的时候做了这么一个集群，一般做了集群的话，那肯定就需要这么一个高可用的负载均衡器来实现流量的分发，如果使用的是haproxy,比如一台rebbitmq的节点突然宕机或者网卡失效，那么虽然RabbitMQ集群没有任何故障，但是对于外界的客户端来说所有的连接都会被断开，结果将是灾难性的。确保负载均衡服务的可靠性同样显得十分的重要。这里就引入Keepalived工具，它能够通过自身健康检查、资源接管功能做高可用（双机热备），实现故障转移。

Keepalived采用VRRP（Virtual Router Redundancy Protocol，虚拟路由冗余协议），以软件的形式实现服务器热备功能。通常情况下是将两台Linux服务器组成一个热备组（Master和Backup），同一时间热备组内只有一台主服务器Master提供服务，同时Master会虚拟出一个公用的虚拟IP地址，简称VIP。这个VIP只存在在Master上并对外提供服务。如果Keepalived检测到Master宕机或者服务故障，备份服务器Backup会自动接管VIP称为Master，Keepalived并将原Master从热备组中移除。当原Master恢复后，会自动加入到热备组，默认再抢占称为Master，起到故障转移的功能。

Keepalived工作在OSI模型中的第3层、第4层和第7层。
工作在第3层是指Keepalived会定期向热备组中的服务器发送一个ICMP数据包来判断某台服务器是否故障，如果故障则将这台服务器从热备组移除。
工作在第4层是指Keepalived以TCP端口的状态判断服务器是否故障，比如检测RabbitMQ的5672端口，如果故障则将这台服务器从热备组中移除。
工作在第7层是指Keepalived根据用户设定的策略（通常是一个自定义的检测脚本）判断服务器上的程序是否正常运行，如果故障将这台服务器从热备组移除。

首先需要去Keepalived的官网下载Keepalived的安装文件，目前最新的版本为：keepalived-2.0.20.tar.gz，下载地址为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]

解压

[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

出现报错：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

安装后重新再执行
[root@VM_0_8_centos keepalived-2.0.20]# ./configure --prefix=/opt/keepalived --with-init=SYSV

再次报错，说这个版本不支持ipv6，需要安装依赖包
*** 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

安装完依赖包再次执行

[root@VM_0_8_centos keepalived-2.0.20]# ./configure --prefix=/opt/keepalived --with-init=SYSV

编译

[root@VM_0_8_centos keepalived-2.0.20]# make && make install

将启动文件放到/etc/init.d下，可以使用service来启动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

启动失败，查看报错，这里提示 Unable to find configuration file /etc/keepalived/keepalived.conf，没有发现我们的配置文件的地址，这里是因为我们在安装的时候指定了自己的安装路径

[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

找出放置我们配置文件的地方，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

在最后一行添加我们配置文件的地址

[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启动成功

[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进行启动停止

[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.

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