使用Helm管理kubernetes应用
Helm是一个kubernetes应用的包管理工具，用来管理charts——预先配置好的安装包资源，有点类似于Ubuntu的APT和CentOS中的yum。
Helm chart是用来封装kubernetes原生应用程序的yaml文件，可以在你部署应用的时候自定义应用程序的一些metadata，便与应用程序的分发。
Helm和charts的主要作用：
- 应用程序封装
- 版本管理
- 依赖检查
- 便于应用程序分发
安装Helm
前提要求
Kubernetes1.5以上版本，集群可访问到的镜像仓库。
首先需要安装helm客户端
curl https://raw.githubusercontent.com/kubernetes/helm/master/scripts/get > get_helm.sh
chmod 700 get_helm.sh
./get_helm.sh
创建tiller的serviceaccount和clusterrolebinding
kubectl create serviceaccount --namespace kube-system tiller
kubectl create clusterrolebinding tiller-cluster-rule --clusterrole=cluster-admin --serviceaccount=kube-system:tiller
然后安装helm服务端tiller
helm init -i sz-pg-oam-docker-hub-001.tendcloud.com/library/kubernetes-helm-tiller:v2.3.1
我们使用-i指定自己的镜像，因为官方的镜像因为某些原因无法拉取。
为应用程序设置serviceAccount：
kubectl patch deploy --namespace kube-system tiller-deploy -p '{"spec":{"template":{"spec":{"serviceAccount":"tiller"}}}}'
检查是否安装成功：
$ kubectl -n kube-system get pods|grep tiller
tiller-deploy-2372561459-f6p0z 1/1 Running 0 1h
$ helm version
Client: &version.Version{SemVer:"v2.3.1", GitCommit:"32562a3040bb5ca690339b9840b6f60f8ce25da4", GitTreeState:"clean"}
Server: &version.Version{SemVer:"v2.3.1", GitCommit:"32562a3040bb5ca690339b9840b6f60f8ce25da4", GitTreeState:"clean"}
创建自己的chart
我们创建一个名为mychart的chart，看一看chart的文件结构。
$ helm create mongodb
$ tree mongodb
mongodb
├── Chart.yaml
├── charts
├── templates
│ ├── NOTES.txt
│ ├── _helpers.tpl
│ ├── deployment.yaml
│ └── service.yaml
└── values.yaml
2 directories, 6 files
模板
Templates目录下是yaml文件的模板，遵循Go template语法。使用过Hugo的静态网站生成工具的人应该对此很熟悉。
我们查看下deployment.yaml文件的内容。
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: {{ template "fullname" . }}
labels:
chart: "{{ .Chart.Name }}-{{ .Chart.Version | replace "+" "_" }}"
spec:
replicas: {{ .Values.replicaCount }}
template:
metadata:
labels:
app: {{ template "fullname" . }}
spec:
containers:
- name: {{ .Chart.Name }}
image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
imagePullPolicy: {{ .Values.image.pullPolicy }}
ports:
- containerPort: {{ .Values.service.internalPort }}
livenessProbe:
httpGet:
path: /
port: {{ .Values.service.internalPort }}
readinessProbe:
httpGet:
path: /
port: {{ .Values.service.internalPort }}
resources:
{{ toYaml .Values.resources | indent 12 }}
这是该应用的Deployment的yaml配置文件，其中的双大括号包扩起来的部分是Go template，其中的Values是在values.yaml文件中定义的：
# Default values for mychart.
# This is a YAML-formatted file.
# Declare variables to be passed into your templates.
replicaCount: 1
image:
repository: nginx
tag: stable
pullPolicy: IfNotPresent
service:
name: nginx
type: ClusterIP
externalPort: 80
internalPort: 80
resources:
limits:
cpu: 100m
memory: 128Mi
requests:
cpu: 100m
memory: 128Mi
比如在Deployment.yaml中定义的容器镜像image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"其中的：
.Values.image.repository就是nginx.Values.image.tag就是stable
以上两个变量值是在create chart的时候自动生成的默认值。
检查配置和模板是否有效
当使用kubernetes部署应用的时候实际上讲templates渲染成最终的kubernetes能够识别的yaml格式。
使用helm install --dry-run --debug <chart_dir>命令来验证chart配置。该输出中包含了模板的变量配置与最终渲染的yaml文件。
$ helm install --dry-run --debug mychart
Created tunnel using local port: '58406'
SERVER: "localhost:58406"
CHART PATH: /Users/jimmy/Workspace/github/bitnami/charts/incubator/mean/charts/mychart
NAME: named-jackal
REVISION: 1
RELEASED: Tue Oct 24 18:57:13 2017
CHART: mychart-0.1.0
USER-SUPPLIED VALUES:
{}
COMPUTED VALUES:
image:
pullPolicy: IfNotPresent
repository: nginx
tag: stable
replicaCount: 1
resources:
limits:
cpu: 100m
memory: 128Mi
requests:
cpu: 100m
memory: 128Mi
service:
externalPort: 80
internalPort: 80
name: nginx
type: ClusterIP
HOOKS:
MANIFEST:
---
# Source: mychart/templates/service.yaml
apiVersion: v1
kind: Service
metadata:
name: named-jackal-mychart
labels:
chart: "mychart-0.1.0"
spec:
type: ClusterIP
ports:
- port: 80
targetPort: 80
protocol: TCP
name: nginx
selector:
app: named-jackal-mychart
---
# Source: mychart/templates/deployment.yaml
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: named-jackal-mychart
labels:
chart: "mychart-0.1.0"
spec:
replicas: 1
template:
metadata:
labels:
app: named-jackal-mychart
spec:
containers:
- name: mychart
image: "nginx:stable"
imagePullPolicy: IfNotPresent
ports:
- containerPort: 80
livenessProbe:
httpGet:
path: /
port: 80
readinessProbe:
httpGet:
path: /
port: 80
resources:
limits:
cpu: 100m
memory: 128Mi
requests:
cpu: 100m
memory: 128Mi
部署todo测试案例
$ git clone https://github.com/bitnami/charts.git
$ cd charts/incubator/mean
$ helm dep list
NAME VERSION REPOSITORY STATUS
mongodb 0.4.x https://kubernetes-charts.storage.googleapis.com/ missing
缺少mongodb的依赖，需要更新一下chart。
$ helm dep update
Hang tight while we grab the latest from your chart repositories...
...Unable to get an update from the "local" chart repository (http://127.0.0.1:8879/charts):
Get http://127.0.0.1:8879/charts/index.yaml: dial tcp 127.0.0.1:8879: getsockopt: connection refused
...Successfully got an update from the "stable" chart repository
Update Complete. ⎈Happy Helming!⎈
Saving 1 charts
Downloading mongodb from repo https://kubernetes-charts.storage.googleapis.com/
所有的image都在 values.yaml 文件中配置。
下载缺失的chart。
$ helm dep build
Hang tight while we grab the latest from your chart repositories...
...Unable to get an update from the "local" chart repository (http://127.0.0.1:8879/charts):
Get http://127.0.0.1:8879/charts/index.yaml: dial tcp 127.0.0.1:8879: getsockopt: connection refused
...Successfully got an update from the "stable" chart repository
Update Complete. ⎈Happy Helming!⎈
Saving 1 charts
Downloading mongodb from repo https://kubernetes-charts.storage.googleapis.com/