helm的template语法学习
一、Chart文件结构
[root@master ~]# helm create my-nginx
Creating my-nginx
[root@master ~]# tree my-nginx/
my-nginx/
├── charts
├── Chart.yaml
├── templates
│ ├── deployment.yaml
│ ├── _helpers.tpl
│ ├── ingress.yaml
│ ├── NOTES.txt
│ ├── serviceaccount.yaml
│ ├── service.yaml
│ └── tests
│ └── test-connection.yaml
└── values.yaml
templates/ 存放k8s的部署资源模板，通过渲染变量得到部署文件
values.yaml 用来存放templates默认值
Chart.yaml 一些对chart的描述description
deployment.yaml 一个基础deployment描述文件
_helpers.tpl 存放能够复用的模板
helm get manifest
检索和查看release加载的实际模板
示例变量使用
apiVersion: v1
kind: ConfigMap
metadata:
name: {{ .Release.Name }}-configmap
data:
myvalue: "Hello World"
$ helm install clunky-serval ./mychart
$ helm get manifest clunky-serval
---
# Source: my-nginx/templates/configmap.yaml
apiVersion: v1
kind: ConfigMap
metadata:
name: clunky-serval-configmap
data:
myvalue: "Hello World"
二、内置对象
内置对象始终是大写字母开头，符合Go的命名约定
{{ .Release.Name }}
Release.Name: chart的实例名，release name
Release.Namespace: 实例要安装的命名空间
Release.IsUpgrade: This is set to true if the current operation is an upgrade or rollback.
Release.IsInstall: This is set to true if the current operation is an install.
Release.Revision: 此版本的修订号。在安装时，该值为1，并且每次升级和回滚时都会增加
Release.Service: The service that is rendering the present template. On Helm, this is always Helm.
#参数传递，覆盖values.yaml的值
$ helm install --set foo=bar ./mychart
{{ .Values.image.pullPolicy }}
{{ template “open.fullname” . }}
三、管道、常用函数
3.1、quote 函数，将值渲染模板时候，以字符串方式引用
apiVersion: v1
kind: ConfigMap
metadata:
name: {{ .Release.Name }}-configmap
data:
myvalue: "Hello World"
drink: {{ .Values.favorite.drink | quote }}
food: {{ .Values.favorite.food | upper | quote }}
============================================================================
# Source: mychart/templates/configmap.yaml
apiVersion: v1
kind: ConfigMap
metadata:
name: trendsetting-p-configmap
data:
myvalue: "Hello World"
drink: "coffee"
food: "PIZZA"
3.2、upper 函数，将小写字母转换为大写
3.3、repeat 函数，写法repeat n 是将参数复制n遍
3.4、default 函数，用法default "tee" 给一个默认的参数，建议将静态的参数都写入values.yaml
drink: {{ .Values.favorite.drink | default "tea" | quote }}
3.5、title 函数，首字母大写
3.6、indent 函数，缩进字符，以空格为单位
{{ toYaml .Values.strategy | indent 4 }}
四、流程控制
1.1、helm的模板语言提供以下几种控制结构
-
if/else用于创建条件块，以下值的内容，被认为flase-
布尔值false
-
数字零
-
一个空字符串
-
一个
nil（空或空） -
一个空的集合（
map，slice，tuple，dict，array）
-
-
with指定范围{{ with PIPELINE }} # restricted scope {{ end }} -
range，提供“针对每个”样式的循环
除此之外，它还提供了一些声明和使用命名模板段的操作：
define在模板中声明一个新的模板template导入指定名称模板block声明一种特殊的可填充模板区域
1.2、if/else的基本结构
{{ if PIPELINE }}
# Do something
{{ else if OTHER PIPELINE }}
# Do something else
{{ else }}
# Default case
{{ end }}
通过以下例子发现模板引擎在运行 {{ if eq .Values.favorite.drink “coffee” }} 里面的流程控制时会删除掉所有内容，但是会完全保留空白
apiVersion: v1
kind: ConfigMap
metadata:
name: {{ .Release.Name }}-configmap
data:
myvalue: "Hello World"
drink: {{ .Values.favorite.drink | default "tea" | quote }}
food: {{ .Values.favorite.food | upper | quote }}
{{ if eq .Values.favorite.drink "coffee" }}
mug: true
{{ end }}
=========================================================================
helm install --debug --dry-run my-config ../my-nginx/
# Source: my-nginx/templates/configmap.yaml
apiVersion: v1
kind: ConfigMap
metadata:
name: aaaa-configmap
data:
myvalue: "Hello World"
drink: "coffee"
food: "PIZZA"
mug: true
添加特殊字符，告诉模板引擎压缩移除空白行
apiVersion: v1
kind: ConfigMap
metadata:
name: {{ .Release.Name }}-configmap
data:
myvalue: "Hello World"
drink: {{ .Values.favorite.drink | default "tea" | quote }}
food: {{ .Values.favorite.food | upper | quote }}
{{- if eq .Values.favorite.drink "coffee" }}
mug: true
{{- end }}
===============================================================================
helm install --debug --dry-run my-config ../my-nginx/
# Source: my-nginx/templates/configmap.yaml
apiVersion: v1
kind: ConfigMap
metadata:
name: aaaa-configmap
data:
myvalue: "Hello World"
drink: "coffee"
food: "PIZZA"
mug: true
===============================================================================
#使用*代表将要移除的换行符
apiVersion: v1
kind: ConfigMap
metadata:
name: {{ .Release.Name }}-configmap
data:
myvalue: "Hello World"
drink: {{ .Values.favorite.drink | default "tea" | quote }}
food: {{ .Values.favorite.food | upper | quote }}*
**{{- if eq .Values.favorite.drink "coffee" }}
mug: true*
**{{- end }}
通过使用在模板标识{{后面添加破折号和空格{{-来表示将左边空白删除，而在}}前面添加一个空格和破折号-}}表示应该删除右边的空格，另外需要注意的是换行符也是空格！
1.3、with使用示例
apiVersion: v1
kind: ConfigMap
metadata:
name: {{ .Release.Name }}-configmap
data:
myvalue: "Hello World"
{{- with .Values.favorite }}
drink: {{ .drink | default "tea" | quote }}
food: {{ .food | upper | quote }}
{{- end }}
#以下使用会出现错误，Release.Name不在with的作用范围，在受限范围内，将无法使用从父范围访问其他对象
{{- with .Values.favorite }}
drink: {{ .drink | default "tea" | quote }}
food: {{ .food | upper | quote }}
release: {{ .Release.Name }}
{{- end }}
1.4、range用法示例
cat values.yaml
favorite:
drink: coffee
food: pizza
pizzaToppings:
- mushrooms
- cheese
- peppers
- onions
==========================================================================
apiVersion: v1
kind: ConfigMap
metadata:
name: {{ .Release.Name }}-configmap
data:
myvalue: "Hello World"
{{- with .Values.favorite }}
drink: {{ .drink | default "tea" | quote }}
food: {{ .food | upper | quote }}
{{- end }}
toppings: |-
{{- range .Values.pizzaToppings }}
- {{ . | title | quote }}
{{- end }}
=============================================================================
# Source: my-nginx/templates/configmap.yaml
apiVersion: v1
kind: ConfigMap
metadata:
name: aaaa-configmap
data:
myvalue: "Hello World"
drink: "coffee"
food: "PIZZA"
toppings: |-
- "Mushrooms"
- "Cheese"
- "Peppers"
- "Onions"
五、定义和使用模板
{{ define "MY.NAME" }}
# body of template here
{{ end }}
Helm charts 将模板写入到一个特定的文件里面, 通常用
_helpers.tpl.
按照惯例，define函数应该有一个简单的文档块（{{/* ... */}}）描述它们的作用
{{/* test labels */}}
{{- define "mychart.labels" }}
labels:
generator: helm
date: {{ now | htmlDate }}
{{- end }}
apiVersion: v1
kind: ConfigMap
metadata:
name: {{ .Release.Name }}-configmap
{{- template "mychart.labels" }}
data:
myvalue: "Hello World"
{{- range $key, $val := .Values.favorite }}
{{ $key }}: {{ $val | quote }}
{{- end }}
=============================================================================
# Source: mychart/templates/configmap.yaml
apiVersion: v1
kind: ConfigMap
metadata:
name: running-panda-configmap
labels:
generator: helm
date: 2016-11-02
data:
myvalue: "Hello World"
drink: "coffee"
food: "pizza"
六、模板调试
调试模板可能会很棘手，因为渲染完成的模板已发送到Kubernetes API服务器，该服务器可能会因为格式化错误的原因而拒绝执行YAML文件或者执行发生错误，所以在执行前最好调试一下模板内容。
helm lint检查chart包可能存在的问题helm installorhelm template --debug: 不安装chart，让服务渲染模板后，返回清单文件helm get manifest: 检索和查看release加载的实际模板
下面给个示例说明，部分冗余代码使用省略号代替
[root@jxy-master helm-chart]# helm install test-nginx --dry-run --debug my-nginx/
install.go:158: [debug] Original chart version: ""
install.go:175: [debug] CHART PATH: /root/helm-chart/my-nginx
NAME: test-nginx
LAST DEPLOYED: Fri May 29 11:10:49 2020
NAMESPACE: default
STATUS: pending-install
REVISION: 1
USER-SUPPLIED VALUES:
{}
COMPUTED VALUES:
...
HOOKS:
---
# Source: my-nginx/templates/tests/test-connection.yaml
...
MANIFEST:
---
# Source: my-nginx/templates/serviceaccount.yaml
...
---
# Source: my-nginx/templates/service.yaml
apiVersion: v1
kind: Service
metadata:
name: test-nginx-my-nginx
labels:
helm.sh/chart: my-nginx-0.1.0
...
spec:
type: ClusterIP
ports:
- port: 80
targetPort: http
protocol: TCP
name: http
selector:
app.kubernetes.io/name: my-nginx
app.kubernetes.io/instance: test-nginx
---
# Source: my-nginx/templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: test-nginx-my-nginx
labels:
helm.sh/chart: my-nginx-0.1.0
...
spec:
replicas: 1
selector:
matchLabels:
app.kubernetes.io/name: my-nginx
app.kubernetes.io/instance: test-nginx
template:
metadata:
labels:
app.kubernetes.io/name: my-nginx
app.kubernetes.io/instance: test-nginx
spec:
serviceAccountName: test-nginx-my-nginx
securityContext:
{}
containers:
- name: my-nginx
securityContext:
{}
image: "nginx:1.16.0"
imagePullPolicy: IfNotPresent
...
{}
NOTES:
1. Get the application URL by running these commands:
export POD_NAME=$(kubectl get pods --namespace default -l "app.kubernetes.io/name=my-nginx,app.kubernetes.io/instance=test-nginx" -o jsonpath="{.items[0].metadata.name}")
echo "Visit http://127.0.0.1:8080 to use your application"
kubectl --namespace default port-forward $POD_NAME 8080:80
创建NOTES.txt文件
Helm可以为用户打印出一些有用的信息。使用模板可以高度自定义此信息，在安装完release后打印一些帮助信息，来帮助我们更好的使用该chart