Helm Chart开发入门
本文我们展示如何开发一个简单的Chart，其中包含了一个Deployment和Service简单的Template，最后安装该Chart。整个Chart的代码已经放到https://github.com/twingao/httpbin。
先使用helm create命令创建一个Chart。
helm create httpbin
Creating httpbin
查看httpbin的目录结构。
tree httpbin -a
httpbin
├── charts
├── Chart.yaml
├── .helmignore
├── templates
│ ├── deployment.yaml
│ ├── _helpers.tpl
│ ├── ingress.yaml
│ ├── NOTES.txt
│ ├── serviceaccount.yaml
│ ├── service.yaml
│ └── tests
│ └── test-connection.yaml
└── values.yaml
3 directories, 10 files
Helm规范了Chart的目录和文件结构，这些目录或者文件都有确定的用途。
-
charts/，包含其它Chart，称之为Sub Chart，或者依赖Chart。
-
Chart.yaml，包含Chart的说明，可在从模板中访问Chart定义的值。
-
.helmignore，定义了在helm package时哪些文件不会打包到Chart包tgz中。
-
ci/，缺省没有该目录，持续集成的一些脚本。
-
templates/，用于放置模板文件，主要定义提交给Kubernetes的资源yaml文件。安装Chart时，Helm会根据chart.yaml、values.yam以及命令行提供的值对Templates进行渲染，最后会将渲染的资源提交给Kubernetes。
-
_helpers.tpl，定义了一些可重用的模板片断，此文件中的定义在任何资源定义模板中可用。
-
NOTES.txt，提供了安装后的使用说明，在Chart安装和升级等操作后，
-
tests/，包含了测试用例。测试用例是pod资源，指定一个的命令来运行容器。容器应该成功退出（exit 0），测试被认为是成功的。该pod定义必须包含helm测试hook注释之一：helm.sh/hook: test-success或helm.sh/hook: test-failure。
-
values.yaml，values文件对模板很重要，该文件包含Chart默认值。Helm渲染template时使用这些值。
查看values.yaml文件，需要做一些配置修改：
- 将镜像改为image.repository=docker.io/kennethreitz/httpbin。
- 不创建serviceAccount，serviceAccount.create=false
- 为了Kubernetes集群外能访问Service，将type改为NodePort。并增加一个参数，为nodePort配置一个固定端口。
values.yaml修改如下：
cd httpbin/
vi values.yaml
# Default values for httpbin.
# This is a YAML-formatted file.
# Declare variables to be passed into your templates.
replicaCount: 1
image:
repository: docker.io/kennethreitz/httpbin
tag: latest
pullPolicy: IfNotPresent
imagePullSecrets: []
nameOverride: ""
fullnameOverride: ""
serviceAccount:
# Specifies whether a service account should be created
create: false
# The name of the service account to use.
# If not set and create is true, a name is generated using the fullname template
name:
podSecurityContext: {}
# fsGroup: 2000
securityContext: {}
# capabilities:
# drop:
# - ALL
# readOnlyRootFilesystem: true
# runAsNonRoot: true
# runAsUser: 1000
service:
type: NodePort
port: 80
nodePort: 30080
ingress:
enabled: false
annotations: {}
# kubernetes.io/ingress.class: nginx
# kubernetes.io/tls-acme: "true"
hosts:
- host: chart-example.local
paths: []
tls: []
# - secretName: chart-example-tls
# hosts:
# - chart-example.local
resources: {}
# We usually recommend not to specify default resources and to leave this as a conscious
# choice for the user. This also increases chances charts run on environments with little
# resources, such as Minikube. If you do want to specify resources, uncomment the following
# lines, adjust them as necessary, and remove the curly braces after 'resources:'.
# limits:
# cpu: 100m
# memory: 128Mi
# requests:
# cpu: 100m
# memory: 128Mi
nodeSelector: {}
tolerations: []
affinity: {}
由于配置了固定的nodePort，所以在service.yaml中增加该参数，并引用了对应的value值。
vi templates/service.yaml
apiVersion: v1
kind: Service
metadata:
name: {{ include "httpbin.fullname" . }}
labels:
{{- include "httpbin.labels" . | nindent 4 }}
spec:
type: {{ .Values.service.type }}
ports:
- port: {{ .Values.service.port }}
targetPort: http
protocol: TCP
name: http
nodePort: {{ .Values.service.nodePort }}
selector:
{{- include "httpbin.selectorLabels" . | nindent 4 }}
查看deployment.yaml，可以看出镜像的tag使用变量{{ .Chart.AppVersion }}，该参数定义在Chart.yaml文件中。
vi templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: {{ include "httpbin.fullname" . }}
labels:
{{- include "httpbin.labels" . | nindent 4 }}
spec:
replicas: {{ .Values.replicaCount }}
selector:
matchLabels:
{{- include "httpbin.selectorLabels" . | nindent 6 }}
template:
metadata:
labels:
{{- include "httpbin.selectorLabels" . | nindent 8 }}
spec:
{{- with .Values.imagePullSecrets }}
imagePullSecrets:
{{- toYaml . | nindent 8 }}
{{- end }}
serviceAccountName: {{ include "httpbin.serviceAccountName" . }}
securityContext:
{{- toYaml .Values.podSecurityContext | nindent 8 }}
containers:
- name: {{ .Chart.Name }}
securityContext:
{{- toYaml .Values.securityContext | nindent 12 }}
image: "{{ .Values.image.repository }}:{{ .Chart.AppVersion }}"
imagePullPolicy: {{ .Values.image.pullPolicy }}
ports:
- name: http
containerPort: 80
protocol: TCP
livenessProbe:
httpGet:
path: /
port: http
readinessProbe:
httpGet:
path: /
port: http
resources:
{{- toYaml .Values.resources | nindent 12 }}
{{- with .Values.nodeSelector }}
nodeSelector:
{{- toYaml . | nindent 8 }}
{{- end }}
{{- with .Values.affinity }}
affinity:
{{- toYaml . | nindent 8 }}
{{- end }}
{{- with .Values.tolerations }}
tolerations:
{{- toYaml . | nindent 8 }}
{{- end }}
将Chart.yaml文件中的appVersion改为latest。appVersion一般配置为镜像的版本号。
vi Chart.yaml
apiVersion: v2
name: httpbin
description: A Helm chart for Kubernetes
# A chart can be either an 'application' or a 'library' chart.
#
# Application charts are a collection of templates that can be packaged into versioned archives
# to be deployed.
#
# Library charts provide useful utilities or functions for the chart developer. They're included as
# a dependency of application charts to inject those utilities and functions into the rendering
# pipeline. Library charts do not define any templates and therefore cannot be deployed.
type: application
# This is the chart version. This version number should be incremented each time you make changes
# to the chart and its templates, including the app version.
version: 0.1.0
# This is the version number of the application being deployed. This version number should be
# incremented each time you make changes to the application.
appVersion: latest
现在已经开发完成了httpbin的Chart。我们看一下模板的渲染后的效果。
helm template my-release httpbin
---
# Source: httpbin/templates/service.yaml
apiVersion: v1
kind: Service
metadata:
name: my-release-httpbin
labels:
helm.sh/chart: httpbin-0.1.0
app.kubernetes.io/name: httpbin
app.kubernetes.io/instance: my-release
app.kubernetes.io/version: "latest"
app.kubernetes.io/managed-by: Helm
spec:
type: NodePort
ports:
- port: 80
targetPort: http
protocol: TCP
name: http
nodePort: 30080
selector:
app.kubernetes.io/name: httpbin
app.kubernetes.io/instance: my-release
---
# Source: httpbin/templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: my-release-httpbin
labels:
helm.sh/chart: httpbin-0.1.0
app.kubernetes.io/name: httpbin
app.kubernetes.io/instance: my-release
app.kubernetes.io/version: "latest"
app.kubernetes.io/managed-by: Helm
spec:
replicas: 1
selector:
matchLabels:
app.kubernetes.io/name: httpbin
app.kubernetes.io/instance: my-release
template:
metadata:
labels:
app.kubernetes.io/name: httpbin
app.kubernetes.io/instance: my-release
spec:
serviceAccountName: default
securityContext:
{}
containers:
- name: httpbin
securityContext:
{}
image: "docker.io/kennethreitz/httpbin:latest"
imagePullPolicy: IfNotPresent
ports:
- name: http
containerPort: 80
protocol: TCP
livenessProbe:
httpGet:
path: /
port: http
readinessProbe:
httpGet:
path: /
port: http
resources:
{}
---
# Source: httpbin/templates/tests/test-connection.yaml
apiVersion: v1
kind: Pod
metadata:
name: "my-release-httpbin-test-connection"
labels:
helm.sh/chart: httpbin-0.1.0
app.kubernetes.io/name: httpbin
app.kubernetes.io/instance: my-release
app.kubernetes.io/version: "latest"
app.kubernetes.io/managed-by: Helm
annotations:
"helm.sh/hook": test-success
spec:
containers:
- name: wget
image: busybox
command: ['wget']
args: ['my-release-httpbin:80']
restartPolicy: Never
然后我们安装Chart。
cd ..
helm install my-release httpbin
NAME: my-release
LAST DEPLOYED: Sun Mar 29 12:43:29 2020
NAMESPACE: default
STATUS: deployed
REVISION: 1
NOTES:
1. Get the application URL by running these commands:
export NODE_PORT=$(kubectl get --namespace default -o jsonpath="{.spec.ports[0].nodePort}" services my-release-httpbin)
export NODE_IP=$(kubectl get nodes --namespace default -o jsonpath="{.items[0].status.addresses[0].address}")
echo http://$NODE_IP:$NODE_PORT
查看Kubernetes的资源。
kubectl get all
NAME READY STATUS RESTARTS AGE
pod/my-release-httpbin-74956dc94f-mgwcp 1/1 Running 0 104s
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/kubernetes ClusterIP 10.1.0.1 443/TCP 105d
service/my-release-httpbin NodePort 10.1.170.94 80:30080/TCP 104s
NAME READY UP-TO-DATE AVAILABLE AGE
deployment.apps/my-release-httpbin 1/1 1 1 104s
NAME DESIRED CURRENT READY AGE
replicaset.apps/my-release-httpbin-74956dc94f 1 1 1 104s
根据安装说明Notes，可以执行这些命令给出如何访问该服务。
export NODE_PORT=$(kubectl get --namespace default -o jsonpath="{.spec.ports[0].nodePort}" services my-release-httpbin)
export NODE_IP=$(kubectl get nodes --namespace default -o jsonpath="{.items[0].status.addresses[0].address}")
echo http://$NODE_IP:$NODE_PORT
http://192.168.1.55:30080
访问httpbin服务。说明该Chart开发完成，并能够正确安装。
curl -i http://192.168.1.55:30080/status/200
HTTP/1.1 200 OK
Server: gunicorn/19.9.0
Date: Sun, 29 Mar 2020 04:47:41 GMT
Connection: keep-alive
Content-Type: text/html; charset=utf-8
Access-Control-Allow-Origin: *
Access-Control-Allow-Credentials: true
Content-Length: 0
根据上面渲染的Kubernetes资源，httpbin/templates/tests/test-connection.yaml文件定义了测试用例，在Pod中通过wget my-release-httpbin:80来测试该Chart是否安装成功。
helm test my-release
Pod my-release-httpbin-test-connection pending
Pod my-release-httpbin-test-connection pending
Pod my-release-httpbin-test-connection succeeded
NAME: my-release
LAST DEPLOYED: Sun Mar 29 12:43:29 2020
NAMESPACE: default
STATUS: deployed
REVISION: 1
TEST SUITE: my-release-httpbin-test-connection
Last Started: Sun Mar 29 12:49:13 2020
Last Completed: Sun Mar 29 12:49:31 2020
Phase: Succeeded
NOTES:
1. Get the application URL by running these commands:
export NODE_PORT=$(kubectl get --namespace default -o jsonpath="{.spec.ports[0].nodePort}" services my-release-httpbin)
export NODE_IP=$(kubectl get nodes --namespace default -o jsonpath="{.items[0].status.addresses[0].address}")
echo http://$NODE_IP:$NODE_PORT
.helmignore定义了在helm package时哪些文件不会打包到Chart包tgz中。可以预览一下Helm预定义忽略了哪些文件。也可以自行增加需要忽略的文件。
vi httpbin/.helmignore
# Patterns to ignore when building packages.
# This supports shell glob matching, relative path matching, and
# negation (prefixed with !). Only one pattern per line.
.DS_Store
# Common VCS dirs
.git/
.gitignore
.bzr/
.bzrignore
.hg/
.hgignore
.svn/
# Common backup files
*.swp
*.bak
*.tmp
*~
# Various IDEs
.project
.idea/
*.tmproj
.vscode/
将Chart打包，tgz包文件中会自动添加Chart.yaml的version参数。
helm package httpbin
Successfully packaged chart and saved it to: /root/httpbin-0.1.0.tgz
ls
httpbin httpbin-0.1.0.tgz