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@ -4,14 +4,16 @@
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经过部署Kubernetes集群章节我们已经可以顺利的部署一个集群用于开发和测试,但是要应用到生产就就不得不考虑master节点的高可用问题,因为现在我们的master节点上的几个服务`kube-apiserver`、`kube-scheduler`和`kube-controller-manager`都是单点的而且都位于同一个节点上,一旦master节点宕机,虽然不应答当前正在运行的应用,将导致kubernetes集群无法变更。本文将引导你创建一个高可用的master节点。
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在大神gzmzj的ansible创建kubernetes集群神作中有讲到如何配置多个Master,但是在实践过程中还是遇到不少坑。需要将坑填上才能工作。
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神作链接地址:https://github.com/mendickxiao/kubeasz/blob/master/docs/00-%E9%9B%86%E7%BE%A4%E8%A7%84%E5%88%92%E5%92%8C%E5%9F%BA%E7%A1%80%E5%8F%82%E6%95%B0%E8%AE%BE%E5%AE%9A.md
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神作链接地址:
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https://github.com/mendickxiao/kubeasz/blob/master/docs/00-%E9%9B%86%E7%BE%A4%E8%A7%84%E5%88%92%E5%92%8C%E5%9F%BA%E7%A1%80%E5%8F%82%E6%95%B0%E8%AE%BE%E5%AE%9A.md
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按照神作的描述,实际上是通过keepalived + haproxy实现的,其中keepalived是提供一个VIP,通过VIP关联所有的Master节点;然后haproxy提供端口转发功能。由于VIP还是存在Master的机器上的,默认配置API Server的端口是6443,所以我们需要将另外一个端口关联到这个VIP上,一般用8443。
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根据神作的实践,我发现需要在Master手工安装keepalived, haproxy。
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```
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yum install keepalived
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yum install haproxy
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```
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需要将haproxy默认的配置文件balance从source修改为roundrobin方式。haproxy的配置文件haproxy.cfg默认路径是/etc/haproxy/haproxy.cfg。另外需要手工创建/run/haproxy的目录,否则haproxy会启动失败。
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*注意*
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balance指定的负载均衡方式是roundrobin方式,默认是source方式。在我的测试中,source方式不工作。
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server指定的就是实际的Master节点地址以及真正工作的端口号,这里是6443。有多少台Master就写多少条记录。
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```
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# haproxy.cfg sample
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global
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log /dev/log local0
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**balance roundrobin**
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server s1 **Master 1的IP地址**:6443 check inter 10000 fall 2 rise 2 weight 1
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server s2 **Master 2的IP地址**:6443 check inter 10000 fall 2 rise 2 weight 1
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```
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修改keepalived的配置文件,配置正确的VIP。keepalived的配置文件keepalived.conf的默认路径是/etc/keepalived/keepalived.conf
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*注意*
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virtual_router_id决定当前VIP的路由号,实际上VIP提供了一个虚拟的路由功能,该VIP在同一个子网内必须是唯一。
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virtual_ipaddress提供的就是VIP的地址,该地址在子网内必须是空闲未必分配的。
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```
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# keepalived.cfg sample
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global_defs {
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**10.86.13.36**
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}
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}
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```
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配置好后,那么先启动主Master的keepalived和haproxy。
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```
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systemctl enable keepalived
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systemctl start keepalived
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systemctl enable haproxy
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systemctl start haproxy
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```
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然后使用ip a s命令查看是否有VIP地址分配。如果看到VIP地址已经成功分配在eth0网卡上,说明keepalived启动成功。
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```
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[root@kube32 ~]# ip a s
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1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1
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link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
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valid_lft forever preferred_lft forever
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inet6 fe80::250:56ff:fea9:d5be/64 scope link
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valid_lft forever preferred_lft forever
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```
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更保险方法还可以通过systemctl status keepalived -l看看keepalived的状态
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```
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[root@kube32 ~]# systemctl status keepalived -l
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● keepalived.service - LVS and VRRP High Availability Monitor
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Loaded: loaded (/usr/lib/systemd/system/keepalived.service; enabled; vendor preset: disabled)
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Mar 20 04:51:15 kube32 Keepalived_vrrp[13450]: VRRP_Instance(VI-kube-master) Dropping received VRRP packet...
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**Mar 20 04:51:18 kube32 Keepalived_vrrp[13450]: (VI-kube-master): ip address associated with VRID 51 not present in MASTER advert : 10.86.13.36
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Mar 20 04:51:18 kube32 Keepalived_vrrp[13450]: bogus VRRP packet received on eth0 !!!**
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```
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然后通过systemctl status haproxy -l看haproxy的状态
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```
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[root@kube32 ~]# systemctl status haproxy -l
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● haproxy.service - HAProxy Load Balancer
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Loaded: loaded (/usr/lib/systemd/system/haproxy.service; enabled; vendor preset: disabled)
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├─15116 /usr/sbin/haproxy-systemd-wrapper -f /etc/haproxy/haproxy.cfg -p /run/haproxy.pid
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├─15117 /usr/sbin/haproxy -f /etc/haproxy/haproxy.cfg -p /run/haproxy.pid -Ds
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└─15118 /usr/sbin/haproxy -f /etc/haproxy/haproxy.cfg -p /run/haproxy.pid -Ds
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```
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这个时候通过kubectl version命令,可以获取到kubectl的服务器信息。
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```
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[root@kube32 ~]# kubectl version
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**Client Version: version.Info{Major:"1", Minor:"9", GitVersion:"v1.9.1", GitCommit:"3a1c9449a956b6026f075fa3134ff92f7d55f812", GitTreeState:"clean", BuildDate:"2018-01-03T22:31:01Z", GoVersion:"go1.9.2", Compiler:"gc", Platform:"linux/amd64"}
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Server Version: version.Info{Major:"1", Minor:"9", GitVersion:"v1.9.1", GitCommit:"3a1c9449a956b6026f075fa3134ff92f7d55f812", GitTreeState:"clean", BuildDate:"2018-01-03T22:18:41Z", GoVersion:"go1.9.2", Compiler:"gc", Platform:"linux/amd64"}**
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```
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这个时候说明你的keepalived和haproxy都是成功的。这个时候你可以依次将你其他Master节点的keepalived和haproxy启动。
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此时,你通过ip a s命令去查看其中一台Master(*非主Master*)的时候,你看不到VIP,这个是正常的,因为VIP永远只在主Master节点上,只有当主Master节点挂掉后,才会切换到其他Master节点上。
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```
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[root@kube31 ~]# ip a s
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1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1
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link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
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valid_lft forever preferred_lft forever
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inet6 fe80::250:56ff:fea9:723/64 scope link
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valid_lft forever preferred_lft forever
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```
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在我的实践过程中,通过大神的脚本快速启动多个Master节点,会导致主Master始终获取不了VIP,当时的报错非常奇怪。后来经过我的研究发现,主Master获取VIP是需要时间的,如果多个Master同时启动,会导致冲突。这个不知道是否算是Keepalived的Bug。但是最稳妥的方式还是先启动一台主Master,等VIP确定后再启动其他Master比较靠谱。
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Kubernetes通过Keepalived + Haproxy实现多个Master的高可用部署,你实际上可以采用其他方式,如外部的负载均衡方式。实际上Kubernetes的多个Master是没有主从的,都可以提供一致性服务。Keepalived + Haproxy实际上就是提供了一个简单的负载均衡方式。
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Loading…
Reference in New Issue