Kubernetes高可用master节点安装

北京西山

(题图:鬼见愁@北京西山 Sep 14,2015)

前言

这是和我一步步部署kubernetes集群项目((fork自opsnull))中的一篇文章,下文是结合我之前部署kubernetes的过程产生的kuberentes环境,部署master节点的kube-apiserverkube-controller-managerkube-scheduler的过程。

高可用kubernetes master节点安装

kubernetes master 节点包含的组件:

  • kube-apiserver
  • kube-scheduler
  • kube-controller-manager

目前这三个组件需要部署在同一台机器上。

  • kube-schedulerkube-controller-managerkube-apiserver 三者的功能紧密相关;
  • 同时只能有一个 kube-schedulerkube-controller-manager 进程处于工作状态,如果运行多个,则需要通过选举产生一个 leader;

本文档记录部署一个三个节点的高可用 kubernetes master 集群步骤。(后续创建一个 load balancer 来代理访问 kube-apiserver 的请求)

TLS 证书文件

pem和token.csv证书文件我们在TLS证书和秘钥这一步中已经创建过了。我们再检查一下。

$ ls /etc/kubernetes/ssl
admin-key.pem  admin.pem  ca-key.pem  ca.pem  kube-proxy-key.pem  kube-proxy.pem  kubernetes-key.pem  kubernetes.pem

下载最新版本的二进制文件

有两种下载方式

方式一

github release 页面 下载发布版 tarball,解压后再执行下载脚本

$ wget https://github.com/kubernetes/kubernetes/releases/download/v1.6.0/kubernetes.tar.gz
$ tar -xzvf kubernetes.tar.gz
...
$ cd kubernetes
$ ./cluster/get-kube-binaries.sh
...

方式二

CHANGELOG页面 下载 clientserver tarball 文件

server 的 tarball kubernetes-server-linux-amd64.tar.gz 已经包含了 client(kubectl) 二进制文件,所以不用单独下载kubernetes-client-linux-amd64.tar.gz文件;

$ # wget https://dl.k8s.io/v1.6.0/kubernetes-client-linux-amd64.tar.gz
$ wget https://dl.k8s.io/v1.6.0/kubernetes-server-linux-amd64.tar.gz
$ tar -xzvf kubernetes-server-linux-amd64.tar.gz
...
$ cd kubernetes
$ tar -xzvf  kubernetes-src.tar.gz

将二进制文件拷贝到指定路径

$ cp -r server/bin/{kube-apiserver,kube-controller-manager,kube-scheduler,kubectl,kube-proxy,kubelet} /root/local/bin/

配置和启动 kube-apiserver

创建 kube-apiserver的service配置文件

serivce配置文件/usr/lib/systemd/system/kube-apiserver.service内容:

[Unit]
Description=Kubernetes API Service
Documentation=https://github.com/GoogleCloudPlatform/kubernetes
After=network.target
After=etcd.service

[Service]
EnvironmentFile=-/etc/kubernetes/config
EnvironmentFile=-/etc/kubernetes/apiserver
ExecStart=/usr/bin/kube-apiserver \
	    $KUBE_LOGTOSTDERR \
	    $KUBE_LOG_LEVEL \
	    $KUBE_ETCD_SERVERS \
	    $KUBE_API_ADDRESS \
	    $KUBE_API_PORT \
	    $KUBELET_PORT \
	    $KUBE_ALLOW_PRIV \
	    $KUBE_SERVICE_ADDRESSES \
	    $KUBE_ADMISSION_CONTROL \
	    $KUBE_API_ARGS
Restart=on-failure
Type=notify
LimitNOFILE=65536

[Install]
WantedBy=multi-user.target

/etc/kubernetes/config文件的内容为:

###
# kubernetes system config
#
# The following values are used to configure various aspects of all
# kubernetes services, including
#
#   kube-apiserver.service
#   kube-controller-manager.service
#   kube-scheduler.service
#   kubelet.service
#   kube-proxy.service
# logging to stderr means we get it in the systemd journal
KUBE_LOGTOSTDERR="--logtostderr=true"

# journal message level, 0 is debug
KUBE_LOG_LEVEL="--v=0"

# Should this cluster be allowed to run privileged docker containers
KUBE_ALLOW_PRIV="--allow-privileged=true"

# How the controller-manager, scheduler, and proxy find the apiserver
#KUBE_MASTER="--master=http://sz-pg-oam-docker-test-001.tendcloud.com:8080"
KUBE_MASTER="--master=http://172.20.0.113:8080"

该配置文件同时被kube-apiserver、kube-controller-manager、kube-scheduler、kubelet、kube-proxy使用。

apiserver配置文件/etc/kubernetes/apiserver内容为:

###
## kubernetes system config
##
## The following values are used to configure the kube-apiserver
##
#
## The address on the local server to listen to.
#KUBE_API_ADDRESS="--insecure-bind-address=sz-pg-oam-docker-test-001.tendcloud.com"
KUBE_API_ADDRESS="--advertise-address=172.20.0.113 --bind-address=172.20.0.113 --insecure-bind-address=172.20.0.113"
#
## The port on the local server to listen on.
#KUBE_API_PORT="--port=8080"
#
## Port minions listen on
#KUBELET_PORT="--kubelet-port=10250"
#
## Comma separated list of nodes in the etcd cluster
KUBE_ETCD_SERVERS="--etcd-servers=https://172.20.0.113:2379,172.20.0.114:2379,172.20.0.115:2379"
#
## Address range to use for services
KUBE_SERVICE_ADDRESSES="--service-cluster-ip-range=10.254.0.0/16"
#
## default admission control policies
KUBE_ADMISSION_CONTROL="--admission-control=ServiceAccount,NamespaceLifecycle,NamespaceExists,LimitRanger,ResourceQuota"
#
## Add your own!
KUBE_API_ARGS="--authorization-mode=RBAC --runtime-config=rbac.authorization.k8s.io/v1beta1 --kubelet-https=true --experimental-bootstrap-token-auth --token-auth-file=/etc/kubernetes/token.csv --service-node-port-range=30000-32767 --tls-cert-file=/etc/kubernetes/ssl/kubernetes.pem --tls-private-key-file=/etc/kubernetes/ssl/kubernetes-key.pem --client-ca-file=/etc/kubernetes/ssl/ca.pem --service-account-key-file=/etc/kubernetes/ssl/ca-key.pem --etcd-cafile=/etc/kubernetes/ssl/ca.pem --etcd-certfile=/etc/kubernetes/ssl/kubernetes.pem --etcd-keyfile=/etc/kubernetes/ssl/kubernetes-key.pem --enable-swagger-ui=true --apiserver-count=3 --audit-log-maxage=30 --audit-log-maxbackup=3 --audit-log-maxsize=100 --audit-log-path=/var/lib/audit.log --event-ttl=1h"
  • --authorization-mode=RBAC 指定在安全端口使用 RBAC 授权模式,拒绝未通过授权的请求;
  • kube-scheduler、kube-controller-manager 一般和 kube-apiserver 部署在同一台机器上,它们使用非安全端口和 kube-apiserver通信;
  • kubelet、kube-proxy、kubectl 部署在其它 Node 节点上,如果通过安全端口访问 kube-apiserver,则必须先通过 TLS 证书认证,再通过 RBAC 授权;
  • kube-proxy、kubectl 通过在使用的证书里指定相关的 User、Group 来达到通过 RBAC 授权的目的;
  • 如果使用了 kubelet TLS Boostrap 机制,则不能再指定 --kubelet-certificate-authority--kubelet-client-certificate--kubelet-client-key 选项,否则后续 kube-apiserver 校验 kubelet 证书时出现 ”x509: certificate signed by unknown authority“ 错误;
  • --admission-control 值必须包含 ServiceAccount
  • --bind-address 不能为 127.0.0.1
  • runtime-config配置为rbac.authorization.k8s.io/v1beta1,表示运行时的apiVersion;
  • --service-cluster-ip-range 指定 Service Cluster IP 地址段,该地址段不能路由可达;
  • 缺省情况下 kubernetes 对象保存在 etcd /registry 路径下,可以通过 --etcd-prefix 参数进行调整;

完整 unit 见 kube-apiserver.service

启动kube-apiserver

$ systemctl daemon-reload
$ systemctl enable kube-apiserver
$ systemctl start kube-apiserver
$ systemctl status kube-apiserver

配置和启动 kube-controller-manager

创建 kube-controller-manager的serivce配置文件

文件路径/usr/lib/systemd/system/kube-controller-manager.service

Description=Kubernetes Controller Manager
Documentation=https://github.com/GoogleCloudPlatform/kubernetes

[Service]
EnvironmentFile=-/etc/kubernetes/config
EnvironmentFile=-/etc/kubernetes/controller-manager
ExecStart=/usr/bin/kube-controller-manager \
	    $KUBE_LOGTOSTDERR \
	    $KUBE_LOG_LEVEL \
	    $KUBE_MASTER \
	    $KUBE_CONTROLLER_MANAGER_ARGS
Restart=on-failure
LimitNOFILE=65536

[Install]
WantedBy=multi-user.target

配置文件/etc/kubernetes/controller-manager

###
# The following values are used to configure the kubernetes controller-manager

# defaults from config and apiserver should be adequate

# Add your own!
KUBE_CONTROLLER_MANAGER_ARGS="--address=127.0.0.1 --service-cluster-ip-range=10.254.0.0/16 --cluster-name=kubernetes --cluster-signing-cert-file=/etc/kubernetes/ssl/ca.pem --cluster-signing-key-file=/etc/kubernetes/ssl/ca-key.pem  --service-account-private-key-file=/etc/kubernetes/ssl/ca-key.pem --root-ca-file=/etc/kubernetes/ssl/ca.pem --leader-elect=true"
  • --service-cluster-ip-range 参数指定 Cluster 中 Service 的CIDR范围,该网络在各 Node 间必须路由不可达,必须和 kube-apiserver 中的参数一致;

  • --cluster-signing-* 指定的证书和私钥文件用来签名为 TLS BootStrap 创建的证书和私钥;

  • --root-ca-file 用来对 kube-apiserver 证书进行校验,指定该参数后,才会在Pod 容器的 ServiceAccount 中放置该 CA 证书文件

  • --address 值必须为 127.0.0.1,因为当前 kube-apiserver 期望 scheduler 和 controller-manager 在同一台机器,否则:

  $ kubectl get componentstatuses
  NAME                 STATUS      MESSAGE                                                                                        ERROR
  scheduler            Unhealthy   Get http://127.0.0.1:10251/healthz: dial tcp 127.0.0.1:10251: getsockopt: connection refused   
  controller-manager   Healthy     ok                                                                                             
  etcd-2               Unhealthy   Get http://172.20.0.113:2379/health: malformed HTTP response "\x15\x03\x01\x00\x02\x02"        
  etcd-0               Healthy     {"health": "true"}                                                                             
  etcd-1               Healthy     {"health": "true"}  

参考:https://github.com/kubernetes-incubator/bootkube/issues/64

完整 unit 见 kube-controller-manager.service

启动 kube-controller-manager

$ systemctl daemon-reload
$ systemctl enable kube-controller-manager
$ systemctl start kube-controller-manager

配置和启动 kube-scheduler

创建 kube-scheduler的serivce配置文件

文件路径/usr/lib/systemd/system/kube-scheduler.serivce

[Unit]
Description=Kubernetes Scheduler Plugin
Documentation=https://github.com/GoogleCloudPlatform/kubernetes

[Service]
EnvironmentFile=-/etc/kubernetes/config
EnvironmentFile=-/etc/kubernetes/scheduler
ExecStart=/usr/bin/kube-scheduler \
            $KUBE_LOGTOSTDERR \
            $KUBE_LOG_LEVEL \
            $KUBE_MASTER \
            $KUBE_SCHEDULER_ARGS
Restart=on-failure
LimitNOFILE=65536

[Install]
WantedBy=multi-user.target

配置文件/etc/kubernetes/scheduler

###
# kubernetes scheduler config

# default config should be adequate

# Add your own!
KUBE_SCHEDULER_ARGS="--leader-elect=true --address=127.0.0.1"
  • --address 值必须为 127.0.0.1,因为当前 kube-apiserver 期望 scheduler 和 controller-manager 在同一台机器;

完整 unit 见 kube-scheduler.service

启动 kube-scheduler

$ systemctl daemon-reload
$ systemctl enable kube-scheduler
$ systemctl start kube-scheduler

验证 master 节点功能

$ kubectl get componentstatuses
NAME                 STATUS    MESSAGE              ERROR
scheduler            Healthy   ok                   
controller-manager   Healthy   ok                   
etcd-0               Healthy   {"health": "true"}   
etcd-1               Healthy   {"health": "true"}   
etcd-2               Healthy   {"health": "true"}   

后记

当时在配置过程中遇到了问题TLS认证相关的问题,其实就是因为配置apiserver时候etcd的协议写成了http导致的,应该是用https。

Opsnull写的kubernetes高可用master集群部署过程中似乎并没有包括高可用的配置,才云科技的唐继元分享过Kubernetes Master High Availability 高级实践

究竟如何实现kubernetes master的高可用还需要继续探索。

See Also