Kubernetes 主要由以下几个核心组件组成：
etcd保存了整个集群的状态apiserver提供了资源操作的唯一入口，并提供认证、授权、访问控制、API注册和发现等机制controller manager负责维护集群的状态，比如故障检测、自动扩展、滚动更新等scheduler负责资源的调度，按照预定的调度策略将Pod调度到相应的机器上kubelet负责维护容器的生命周期，同时也负责 Volume和网络的管理Container runtime负责镜像管理以及 Pod 和容器的真正运行（CRI）kube-proxy负责为 Service 提供 cluster 内部的服务发现和负载均衡
除了核心组件，还有一些推荐的 Add-ons：
kube-dns负责为整个集群提供 DNS 服务Ingress Controller为服务提供外网入口Heapster提供资源监控Dashboard提供 GUIFederation提供跨可用区的集群Fluentd-elasticsearch提供集群日志采集、存储与查询
Kubernetes 和数据库
数据库容器化是最近的一大热点，那么 Kubernetes 能为数据库带来什么好处呢？
- 故障恢复: Kubernetes 提供故障恢复的功能，数据库应用如果宕掉，Kubernetes 可以将其自动重启，或者将数据库实例迁移到集群中其他节点上
- 存储管理: Kubernetes 提供了丰富的存储接入方案，数据库应用能透明地使用不同类型的存储系统
- 负载均衡: Kubernetes Service 提供负载均衡功能，能将外部访问平摊给不同的数据库实例副本上
- 水平拓展: Kubernetes 可以根据当前数据库集群的资源利用率情况，缩放副本数目，从而提升资源的利用率
目前很多数据库，如：MySQL，MongoDB 和 TiDB 在 Kubernetes 集群中都能运行很良好。
Nebula Graph在Kubernetes中的实践
Nebula Graph 是一个分布式的开源图数据库，主要组件有：Query Engine 的 graphd，数据存储的 storaged，和元数据的 meted。在 Kubernetes 实践过程中，它主要给图数据库 Nebula Graph 带来了以下的好处：
- Kubernetes 能分摊 nebula graphd，metad 和 storaged 不副本之间的负载。graphd，metad 和 storaged 可以通过 Kubernetes 的域名服务自动发现彼此。
- 通过 storageclass，pvc 和 pv 可以屏蔽底层存储细节，无论使用本地卷还是云盘，Kubernetes 均可以屏蔽这些细节。
- 通过 Kubernetes 可以在几秒内成功部署一套 Nebula 集群，Kubernetes 也可以无感知地实现 Nebula 集群的升级。
- Nebula 集群通过 Kubernetes 可以做到自我恢复，单体副本 crash，Kubernetes 可以重新将其拉起，无需运维人员介入。
- Kubernetes 可以根据当前 Nebula 集群的资源利用率情况水平伸缩 Nebula 集群，从而提供集群的性能。
下面来讲解下具体的实践内容。
集群部署
硬件和软件要求
这里主要罗列下本文部署涉及到的机器、操作系统参数
- 操作系统使用的 CentOS-7.6.1810 x86_64
- 虚拟机配置
- 4 CPU
- 8G 内存
- 50G 系统盘
- 50G 数据盘A
- 50G 数据盘B
- Kubernetes 集群版本 v1.16
- Nebula 版本为 v1.0.0-rc3
- 使用本地 PV 作为数据存储
kubernetes 集群规划
以下为集群清单
| 服务器 IP | nebula 实例 | role |
|---|---|---|
| 192.168.0.1 | k8s-master | |
| 192.168.0.2 | graphd, metad-0, storaged-0 | k8s-slave |
| 192.168.0.3 | graphd, metad-1, storaged-1 | k8s-slave |
| 192.168.0.4 | graphd, metad-2, storaged-2 | k8s-slave |
Kubernetes 待部署组件
- 安装 Helm
- 准备本地磁盘，并安装本地卷插件
- 安装 nebula 集群
- 安装 ingress-controller
安装 Helm
Helm 是 Kubernetes 集群上的包管理工具，类似 CentOS 上的 yum，Ubuntu 上的 apt-get。使用 Helm 可以极大地降低使用 Kubernetes 部署应用的门槛。由于本篇文章不做 Helm 详细介绍，有兴趣的小伙伴可自行阅读《Helm 入门指南》
下载安装Helm
使用下面命令在终端执行即可安装 Helm
[root@nebula ~]# wget https://get.helm.sh/helm-v3.0.1-linux-amd64.tar.gz
[root@nebula ~]# tar -zxvf helm/helm-v3.0.1-linux-amd64.tgz
[root@nebula ~]# mv linux-amd64/helm /usr/bin/helm
[root@nebula ~]# chmod +x /usr/bin/helm
查看 Helm 版本
执行 helm version 命令即可查看对应的 Helm 版本，以文本为例，以下为输出结果：
version.BuildInfo{
Version:"v3.0.1",
GitCommit:"7c22ef9ce89e0ebeb7125ba2ebf7d421f3e82ffa",
GitTreeState:"clean",
GoVersion:"go1.13.4"
}
设置本地磁盘
在每台机器上做如下配置
创建 mount 目录
[root@nebula ~]# sudo mkdir -p /mnt/disks
格式化数据盘
[root@nebula ~]# sudo mkfs.ext4 /dev/diskA
[root@nebula ~]# sudo mkfs.ext4 /dev/diskB
挂载数据盘
[root@nebula ~]# DISKA_UUID=$(blkid -s UUID -o value /dev/diskA)
[root@nebula ~]# DISKB_UUID=$(blkid -s UUID -o value /dev/diskB)
[root@nebula ~]# sudo mkdir /mnt/disks/$DISKA_UUID
[root@nebula ~]# sudo mkdir /mnt/disks/$DISKB_UUID
[root@nebula ~]# sudo mount -t ext4 /dev/diskA /mnt/disks/$DISKA_UUID
[root@nebula ~]# sudo mount -t ext4 /dev/diskB /mnt/disks/$DISKB_UUID
[root@nebula ~]# echo UUID=`sudo blkid -s UUID -o value /dev/diskA` /mnt/disks/$DISKA_UUID ext4 defaults 0 2 | sudo tee -a /etc/fstab
[root@nebula ~]# echo UUID=`sudo blkid -s UUID -o value /dev/diskB` /mnt/disks/$DISKB_UUID ext4 defaults 0 2 | sudo tee -a /etc/fstab
部署本地卷插件
[root@nebula ~]# curl https://github.com/kubernetes-sigs/sig-storage-local-static-provisioner/archive/v2.3.3.zip
[root@nebula ~]# unzip v2.3.3.zip
修改 v2.3.3/helm/provisioner/values.yaml
#
# Common options.
#
common:
#
# Defines whether to generate service account and role bindings.
#
rbac: true
#
# Defines the namespace where provisioner runs
#
namespace: default
#
# Defines whether to create provisioner namespace
#
createNamespace: false
#
# Beta PV.NodeAffinity field is used by default. If running against pre-1.10
# k8s version, the `useAlphaAPI` flag must be enabled in the configMap.
#
useAlphaAPI: false
#
# Indicates if PVs should be dependents of the owner Node.
#
setPVOwnerRef: false
#
# Provisioner clean volumes in process by default. If set to true, provisioner
# will use Jobs to clean.
#
useJobForCleaning: false
#
# Provisioner name contains Node.UID by default. If set to true, the provisioner
# name will only use Node.Name.
#
useNodeNameOnly: false
#
# Resync period in reflectors will be random between minResyncPeriod and
# 2*minResyncPeriod. Default: 5m0s.
#
#minResyncPeriod: 5m0s
#
# Defines the name of configmap used by Provisioner
#
configMapName: "local-provisioner-config"
#
# Enables or disables Pod Security Policy creation and binding
#
podSecurityPolicy: false
#
# Configure storage classes.
#
classes:
- name: fast-disks # Defines name of storage classe.
# Path on the host where local volumes of this storage class are mounted
# under.
hostDir: /mnt/fast-disks
# Optionally specify mount path of local volumes. By default, we use same
# path as hostDir in container.
# mountDir: /mnt/fast-disks
# The volume mode of created PersistentVolume object. Default to Filesystem
# if not specified.
volumeMode: Filesystem
# Filesystem type to mount.
# It applies only when the source path is a block device,
# and desire volume mode is Filesystem.
# Must be a filesystem type supported by the host operating system.
fsType: ext4
blockCleanerCommand:
# Do a quick reset of the block device during its cleanup.
# - "/scripts/quick_reset.sh"
# or use dd to zero out block dev in two iterations by uncommenting these lines
# - "/scripts/dd_zero.sh"
# - "2"
# or run shred utility for 2 iteration.s
- "/scripts/shred.sh"
- "2"
# or blkdiscard utility by uncommenting the line below.
# - "/scripts/blkdiscard.sh"
# Uncomment to create storage class object with default configuration.
# storageClass: true
# Uncomment to create storage class object and configure it.
# storageClass:
# reclaimPolicy: Delete # Available reclaim policies: Delete/Retain, defaults: Delete.
# isDefaultClass: true # set as default class
#
# Configure DaemonSet for provisioner.
#
daemonset:
#
# Defines the name of a Provisioner
#
name: "local-volume-provisioner"
#
# Defines Provisioner"s image name including container registry.
#
image: quay.io/external_storage/local-volume-provisioner:v2.3.3
#
# Defines Image download policy, see kubernetes documentation for available values.
#
#imagePullPolicy: Always
#
# Defines a name of the service account which Provisioner will use to communicate with API server.
#
serviceAccount: local-storage-admin
#
# Defines a name of the Pod Priority Class to use with the Provisioner DaemonSet
#
# Note that if you want to make it critical, specify "system-cluster-critical"
# or "system-node-critical" and deploy in kube-system namespace.
# Ref: https://k8s.io/docs/tasks/administer-cluster/guaranteed-scheduling-critical-addon-pods/#marking-pod-as-critical
#
#priorityClassName: system-node-critical
# If configured, nodeSelector will add a nodeSelector field to the DaemonSet PodSpec.
#
# NodeSelector constraint for local-volume-provisioner scheduling to nodes.
# Ref: https://kubernetes.io/docs/concepts/configuration/assign-pod-node/#nodeselector
nodeSelector: {}
#
# If configured KubeConfigEnv will (optionally) specify the location of kubeconfig file on the node.
# kubeConfigEnv: KUBECONFIG
#
# List of node labels to be copied to the PVs created by the provisioner in a format:
#
# nodeLabels:
# - failure-domain.beta.kubernetes.io/zone
# - failure-domain.beta.kubernetes.io/region
#
# If configured, tolerations will add a toleration field to the DaemonSet PodSpec.
#
# Node tolerations for local-volume-provisioner scheduling to nodes with taints.
# Ref: https://kubernetes.io/docs/concepts/configuration/taint-and-toleration/
tolerations: []
#
# If configured, resources will set the requests/limits field to the Daemonset PodSpec.
# Ref: https://kubernetes.io/docs/concepts/configuration/manage-compute-resources-container/
resources: {}
#
# Configure Prometheus monitoring
#
prometheus:
operator:
## Are you using Prometheus Operator?
enabled: false
serviceMonitor:
## Interval at which Prometheus scrapes the provisioner
interval: 10s
# Namespace Prometheus is installed in
namespace: monitoring
## Defaults to whats used if you follow CoreOS [Prometheus Install Instructions](https://github.com/coreos/prometheus-operator/tree/master/helm#tldr)
## [Prometheus Selector Label](https://github.com/coreos/prometheus-operator/blob/master/helm/prometheus/templates/prometheus.yaml#L65)
## [Kube Prometheus Selector Label](https://github.com/coreos/prometheus-operator/blob/master/helm/kube-prometheus/values.yaml#L298)
selector:
prometheus: kube-prometheus
将hostDir: /mnt/fast-disks 改成hostDir: /mnt/disks
将# storageClass: true 改成 storageClass: true
然后执行：
#安装
[root@nebula ~]# helm install local-static-provisioner v2.3.3/helm/provisioner
#查看local-static-provisioner部署情况
[root@nebula ~]# helm list
部署 nebula 集群
下载 nebula helm-chart 包
# 下载nebula
[root@nebula ~]# wget https://github.com/vesoft-inc/nebula/archive/master.zip
# 解压
[root@nebula ~]# unzip master.zip
设置 Kubernetes slave 节点
下面是 Kubernetes 节点列表，我们需要设置 slave 节点的调度标签。可以将 192.168.0.2，192.168.0.3，192.168.0.4 打上 nebula: "yes" 的标签。
| 服务器 IP | kubernetes roles | nodeName |
|---|---|---|
| 192.168.0.1 | master | 192.168.0.1 |
| 192.168.0.2 | worker | 192.168.0.2 |
| 192.168.0.3 | worker | 192.168.0.3 |
| 192.168.0.4 | worker | 192.168.0.4 |
具体操作如下：
[root@nebula ~]# kubectl label node 192.168.0.2 nebula="yes" --overwrite
[root@nebula ~]# kubectl label node 192.168.0.3 nebula="yes" --overwrite
[root@nebula ~]# kubectl label node 192.168.0.4 nebula="yes" --overwrite
调整 nebula helm chart 默认的 values 值
nebula helm-chart 包目录如下:
master/kubernetes/
└── helm
├── Chart.yaml
├── templates
│ ├── configmap.yaml
│ ├── deployment.yaml
│ ├── _helpers.tpl
│ ├── ingress-configmap.yaml
│ ├── NOTES.txt
│ ├── pdb.yaml
│ ├── service.yaml
│ └── statefulset.yaml
└── values.yaml
2 directories, 10 files
我们需要调整 master/kubernetes/values.yaml 里面的 MetadHosts 的值，将这个 IP List 替换本环境的 3 个 k8s worker 的 ip。
MetadHosts:
- 192.168.0.2:44500
- 192.168.0.3:44500
- 192.168.0.4:44500
通过 helm 安装 nebula
# 安装
[root@nebula ~]# helm install nebula master/kubernetes/helm
# 查看
[root@nebula ~]# helm status nebula
# 查看k8s集群上nebula部署情况
[root@nebula ~]# kubectl get pod | grep nebula
nebula-graphd-579d89c958-g2j2c 1/1 Running 0 1m
nebula-graphd-579d89c958-p7829 1/1 Running 0 1m
nebula-graphd-579d89c958-q74zx 1/1 Running 0 1m
nebula-metad-0 1/1 Running 0 1m
nebula-metad-1 1/1 Running 0 1m
nebula-metad-2 1/1 Running 0 1m
nebula-storaged-0 1/1 Running 0 1m
nebula-storaged-1 1/1 Running 0 1m
nebula-storaged-2 1/1 Running 0 1m
部署 Ingress-controller
Ingress-controller 是 Kubernetes 的一个 Add-Ons。Kubernetes 通过 ingress-controller 将 Kubernetes 内部署的服务暴露给外部用户访问。Ingress-controller 还提供负载均衡的功能，可以将外部访问流量平摊给 k8s 中应用的不同的副本。
选择一个节点部署 Ingress-controller
[root@nebula ~]# kubectl get node
NAME STATUS ROLES AGE VERSION
192.168.0.1 Ready master 82d v1.16.1
192.168.0.2 Ready 82d v1.16.1
192.168.0.3 Ready 82d v1.16.1
192.168.0.4 Ready 82d v1.16.1
[root@nebula ~]# kubectl label node 192.168.0.4 ingress=yes
编写 ingress-nginx.yaml 部署文件
apiVersion: v1
kind: Namespace
metadata:
name: ingress-nginx
labels:
app.kubernetes.io/name: ingress-nginx
app.kubernetes.io/part-of: ingress-nginx
---
kind: ConfigMap
apiVersion: v1
metadata:
name: nginx-configuration
namespace: ingress-nginx
labels:
app.kubernetes.io/name: ingress-nginx
app.kubernetes.io/part-of: ingress-nginx
---
kind: ConfigMap
apiVersion: v1
metadata:
name: tcp-services
namespace: ingress-nginx
labels:
app.kubernetes.io/name: ingress-nginx
app.kubernetes.io/part-of: ingress-nginx
---
kind: ConfigMap
apiVersion: v1
metadata:
name: udp-services
namespace: ingress-nginx
labels:
app.kubernetes.io/name: ingress-nginx
app.kubernetes.io/part-of: ingress-nginx
---
apiVersion: v1
kind: ServiceAccount
metadata:
name: nginx-ingress-serviceaccount
namespace: ingress-nginx
labels:
app.kubernetes.io/name: ingress-nginx
app.kubernetes.io/part-of: ingress-nginx
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
name: nginx-ingress-clusterrole
labels:
app.kubernetes.io/name: ingress-nginx
app.kubernetes.io/part-of: ingress-nginx
rules:
- apiGroups:
- ""
resources:
- configmaps
- endpoints
- nodes
- pods
- secrets
verbs:
- list
- watch
- apiGroups:
- ""
resources:
- nodes
verbs:
- get
- apiGroups:
- ""
resources:
- services
verbs:
- get
- list
- watch
- apiGroups:
- "extensions"
- "networking.k8s.io"
resources:
- ingresses
verbs:
- get
- list
- watch
- apiGroups:
- ""
resources:
- events
verbs:
- create
- patch
- apiGroups:
- "extensions"
- "networking.k8s.io"
resources:
- ingresses/status
verbs:
- update
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: Role
metadata:
name: nginx-ingress-role
namespace: ingress-nginx
labels:
app.kubernetes.io/name: ingress-nginx
app.kubernetes.io/part-of: ingress-nginx
rules:
- apiGroups:
- ""
resources:
- configmaps
- pods
- secrets
- namespaces
verbs:
- get
- apiGroups:
- ""
resources:
- configmaps
resourceNames:
# Defaults to "-"
# Here: "-"
# This has to be adapted if you change either parameter
# when launching the nginx-ingress-controller.
- "ingress-controller-leader-nginx"
verbs:
- get
- update
- apiGroups:
- ""
resources:
- configmaps
verbs:
- create
- apiGroups:
- ""
resources:
- endpoints
verbs:
- get
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: RoleBinding
metadata:
name: nginx-ingress-role-nisa-binding
namespace: ingress-nginx
labels:
app.kubernetes.io/name: ingress-nginx
app.kubernetes.io/part-of: ingress-nginx
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: Role
name: nginx-ingress-role
subjects:
- kind: ServiceAccount
name: nginx-ingress-serviceaccount
namespace: ingress-nginx
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
name: nginx-ingress-clusterrole-nisa-binding
labels:
app.kubernetes.io/name: ingress-nginx
app.kubernetes.io/part-of: ingress-nginx
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: ClusterRole
name: nginx-ingress-clusterrole
subjects:
- kind: ServiceAccount
name: nginx-ingress-serviceaccount
namespace: ingress-nginx
---
apiVersion: apps/v1
kind: DaemonSet
metadata:
name: nginx-ingress-controller
namespace: ingress-nginx
labels:
app.kubernetes.io/name: ingress-nginx
app.kubernetes.io/part-of: ingress-nginx
spec:
selector:
matchLabels:
app.kubernetes.io/name: ingress-nginx
app.kubernetes.io/part-of: ingress-nginx
template:
metadata:
labels:
app.kubernetes.io/name: ingress-nginx
app.kubernetes.io/part-of: ingress-nginx
annotations:
prometheus.io/port: "10254"
prometheus.io/scrape: "true"
spec:
hostNetwork: true
tolerations:
- key: "node-role.kubernetes.io/master"
operator: "Exists"
effect: "NoSchedule"
affinity:
podAntiAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
- labelSelector:
matchExpressions:
- key: app.kubernetes.io/name
operator: In
values:
- ingress-nginx
topologyKey: "ingress-nginx.kubernetes.io/master"
nodeSelector:
ingress: "yes"
serviceAccountName: nginx-ingress-serviceaccount
containers:
- name: nginx-ingress-controller
image: quay.io/kubernetes-ingress-controller/nginx-ingress-controller-amd64:0.26.1
args:
- /nginx-ingress-controller
- --configmap=$(POD_NAMESPACE)/nginx-configuration
- --tcp-services-configmap=default/graphd-services
- --udp-services-configmap=$(POD_NAMESPACE)/udp-services
- --publish-service=$(POD_NAMESPACE)/ingress-nginx
- --annotations-prefix=nginx.ingress.kubernetes.io
- --http-port=8000
securityContext:
allowPrivilegeEscalation: true
capabilities:
drop:
- ALL
add:
- NET_BIND_SERVICE
# www-data -> 33
runAsUser: 33
env:
- name: POD_NAME
valueFrom:
fieldRef:
fieldPath: metadata.name
- name: POD_NAMESPACE
valueFrom:
fieldRef:
fieldPath: metadata.namespace
ports:
- name: http
containerPort: 80
- name: https
containerPort: 443
livenessProbe:
failureThreshold: 3
httpGet:
path: /healthz
port: 10254
scheme: HTTP
initialDelaySeconds: 10
periodSeconds: 10
successThreshold: 1
timeoutSeconds: 10
readinessProbe:
failureThreshold: 3
httpGet:
path: /healthz
port: 10254
scheme: HTTP
periodSeconds: 10
successThreshold: 1
timeoutSeconds: 10
部署 ingress-nginx
# 部署
[root@nebula ~]# kubectl create -f ingress-nginx.yaml
# 查看部署情况
[root@nebula ~]# kubectl get pod -n ingress-nginx
NAME READY STATUS RESTARTS AGE
nginx-ingress-controller-mmms7 1/1 Running 2 1m
访问 nebula 集群
查看 ingress-nginx 所在的节点：
[root@nebula ~]# kubectl get node -l ingress=yes -owide
NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME
192.168.0.4 Ready 1d v1.16.1 192.168.0.4 CentOS Linux 7 (Core) 7.6.1810.el7.x86_64 docker://19.3.3
访问 nebula 集群:
[root@nebula ~]# docker run --rm -ti --net=host vesoft/nebula-console:nightly --addr=192.168.0.4 --port=3699
FAQ
如何搭建一套 Kubernetes 集群？
搭建高可用的 Kubernetes 可以参考社区文档：https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/high-availability/
你也可以通过 minikube 搭建本地的 Kubernetes 集群，参考文档：https://kubernetes.io/docs/setup/learning-environment/minikube/
如何调整 nebula 集群的部署参数?
在使用 helm install 时，使用 --set 可以设置部署参数，从而覆盖掉 helm chart 中 values.yaml 中的变量。参考文档：https://helm.sh/docs/intro/using_helm/
如何查看 nebula 集群状况？
使用kubectl get pod | grep nebula命令，或者直接在 Kubernetes dashboard 上查看 nebula 集群的运行状况。
如何使用其他类型的存储？
参考文档：https://kubernetes.io/zh/docs/concepts/storage/storage-classes/
参考资料
- Helm 入门指南
- 详解 k8s 组件 Ingress 边缘路由器并落地到微服务
附录
- Nebula Graph：一个开源的分布式图数据库
- GitHub：https://github.com/vesoft-inc/nebula
- 知乎：zhihu.com/org/nebulagraph/posts
- 微博：weibo.com/nebulagraph
