Add helm chart (#356)

* add example helm chart

Signed-off-by: Matt Butcher <matt.butcher@microsoft.com>

* update to use helloworld-python example

Signed-off-by: Matt Butcher <matt.butcher@microsoft.com>

* Update examples/charts/README.md

Co-Authored-By: Hongchao Deng <hongchaodeng1@gmail.com>

* Update examples/charts/README.md

Co-Authored-By: Hongchao Deng <hongchaodeng1@gmail.com>

Author: technosophos

examples/charts/README.md

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+# Example Charts of OAM Apps
+
+This directory contains example Helm charts that install Open Application Model apps.
+
+Helm is a useful tool for parameterizing AppConfig files. There are various strategies for installing ComponentSchematics:
+
+- They may be bundled into the same chart that manages them, and treated like standard resources
+    - When this chart is upgraded or deleted, components will be updated or deleted
+    - This can be bad if multiple apps share the same components
+    - This can be good if your app configs and components are closely related
+- They may be bundled into the same chart that references them, but managed with hooks
+    - You can configure hooks to not delete components
+    - This solves some of the problems above
+- They may be kept in separate Helm charts
+    - This model is best if you want to have lots of components that can be shared among different app configs
+
+
+## Installing OAM Apps
+
+These examples are built for Helm 3. They can be installed with the following command:
+
+```console
+$ helm install my-hello hello-rudr
+```
+
+They can be uninstalled with `helm delete my-hello`.

examples/charts/hello-rudr/.helmignore

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+# 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

examples/charts/hello-rudr/Chart.yaml

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+apiVersion: v2
+name: hello-rudr
+description: Demonstration of using Helm with Rudr, using the Python example.
+type: application
+version: 0.1.0
+appVersion: 0.1.0

examples/charts/hello-rudr/templates/NOTES.txt

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+This chart is an example of using Helm to install rudr applications.

examples/charts/hello-rudr/templates/_helpers.tpl

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+{{/* vim: set filetype=mustache: */}}
+{{/*
+Expand the name of the chart.
+*/}}
+{{- define "hello-rudr.name" -}}
+{{/* - trunc 63 .Chart.Name | trimSuffix "-" - */}}
+{{ .Chart.name }}
+{{- end -}}
+
+{{/*
+Create a default fully qualified app name.
+We truncate at 63 chars because some Kubernetes name fields are limited to this (by the DNS naming spec).
+If release name contains chart name it will be used as a full name.
+*/}}
+{{- define "hello-rudr.fullname" -}}
+{{- if .Values.fullnameOverride -}}
+{{- .Values.fullnameOverride | trunc 63 | trimSuffix "-" -}}
+{{- else -}}
+{{- $name := default .Chart.Name .Values.nameOverride -}}
+{{- if contains $name .Release.Name -}}
+{{- .Release.Name | trunc 63 | trimSuffix "-" -}}
+{{- else -}}
+{{- printf "%s-%s" .Release.Name $name | trunc 63 | trimSuffix "-" -}}
+{{- end -}}
+{{- end -}}
+{{- end -}}
+
+{{/*
+Create chart name and version as used by the chart label.
+*/}}
+{{- define "hello-rudr.chart" -}}
+{{- printf "%s-%s" .Chart.Name .Chart.Version | replace "+" "_" | trunc 63 | trimSuffix "-" -}}
+{{- end -}}
+
+{{/*
+Common labels
+*/}}
+{{- define "hello-rudr.labels" -}}
+app.kubernetes.io/name: {{ include "hello-rudr.name" . }}
+helm.sh/chart: {{ include "hello-rudr.chart" . }}
+app.kubernetes.io/instance: {{ .Release.Name }}
+{{- if .Chart.AppVersion }}
+app.kubernetes.io/version: {{ .Chart.AppVersion | quote }}
+{{- end }}
+app.kubernetes.io/managed-by: {{ .Release.Service }}
+{{- end -}}

examples/charts/hello-rudr/templates/appconfig.yaml

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+kind: ApplicationConfiguration
+apiVersion: core.oam.dev/v1alpha1
+metadata:
+  name: "{{ .Release.Name }}"
+spec:
+  components:
+    - name: "{{ .Release.Name }}-{{ .Values.appVersion}}"
+      instanceName: "{{ .Release.Name }}-{{ .Values.appVersion}}"
+      parameterValues:
+        - name: target
+          value: "{{ .Values.target }}"
+        - name: port
+          value: "{{ .Values.port }}"
+      traits:
+        - name: ingress
+          parameterValues:
+            - name: hostname
+              value: example.com
+            - name: path
+              value: /
+            - name: service_port
+              value: {{ .Values.port }}

examples/charts/hello-rudr/templates/component.yaml

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+apiVersion: core.oam.dev/v1alpha1
+kind: ComponentSchematic
+metadata:
+  name: "{{.Release.Name}}-{{.Values.appVersion}}"
+spec:
+  name: helloworld-python
+  workloadType: core.oam.dev/v1alpha1.Server
+  containers:
+    - name: foo
+      image: oamdev/helloworld-python:v1
+      env:
+        - name: TARGET
+          fromParam: target
+        - name: PORT
+          fromParam: port
+      ports:
+        - type: tcp
+          containerPort: 9999
+          name: http
+  parameters:
+    - name: target
+      type: string
+      default: World
+    - name: port
+      type: string
+      default: "9999"

examples/charts/hello-rudr/values.yaml

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+# Default values for hello-rudr.
+# This is a YAML-formatted file.
+# Declare variables to be passed into your templates.
+
+replicaCount: 1
+appVersion: v1
+target: Rudr
+port: "9999"