Add populator library and "hello" example

Author: bswartz

.gitignore

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+.idea

example/hello-populator/.gitignore

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+hello-populator

example/hello-populator/Dockerfile

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+FROM gcr.io/distroless/static:latest
+ADD hello-populator /
+ENTRYPOINT ["/hello-populator"]

example/hello-populator/Makefile

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+# Copyright 2021 The Kubernetes Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+export CGO_ENABLED=0
+IMAGE_NAME?=hello-populator
+
+REV=$(shell git describe --long --tags --match='v*' --dirty)
+
+all: build
+
+compile:
+	go build -ldflags '-s -w -X main.version=$(REV)' -o hello-populator main.go
+
+build: compile
+	docker build -f Dockerfile -t $(IMAGE_NAME) .
+
+clean:
+	go clean -i -x ./...
+
+.PHONY: all compile build clean

example/hello-populator/README.md

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+
+# Hello World Populator Example
+
+This example demonstrates an extremely simple populator implementation.
+
+## How To
+
+Install kubernetes 1.17 or later, and enable the AnyVolumeDataSource
+feature gate.
+
+Build the image from code:
+
+`make all`
+
+Make sure you have a repo you can push to, and set the variable
+
+`YOUR_REPO=...`
+
+Push the image to your repo:
+
+```
+docker tag hello-populator:latest ${YOUR_REPO}/hello-populator:latest
+docker push ${YOUR_REPO}/hello-populator:latest
+```
+
+Install the CRD:
+
+`kubectl apply -f crd.yaml`
+
+Install the controller:
+
+`kubectl apply -f deploy.yaml`
+
+Create a CR:
+
+```
+kubectl create -f - << EOF
+apiVersion: hello.k8s.io/v1alpha1
+kind: Hello
+metadata:
+  name: hello1
+spec:
+  fileName: test.txt
+  fileContents: Hello, world!
+EOF
+```
+
+Create a PVC:
+
+```
+kubectl create -f - << EOF
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: pvc1
+spec:
+  accessModes:
+  - ReadWriteOnce
+  resources:
+    requests:
+      storage: 10Mi
+  dataSource:
+    apiGroup: hello.k8s.io
+    kind: Hello
+    name: hello1
+EOF
+```
+
+Create a job to print the contents of the pre-populated file inside the PVC:
+
+```
+kubectl create -f - << EOF
+apiVersion: batch/v1
+kind: Job
+metadata:
+  name: job1
+spec:
+  template:
+    spec:
+      containers:
+        - name: test
+          image: busybox:1.31.1
+          command:
+            - cat
+            - /mnt/test.txt
+          volumeMounts:
+          - mountPath: /mnt
+            name: vol
+      restartPolicy: Never
+      volumes:
+        - name: vol
+          persistentVolumeClaim:
+            claimName: pvc1
+EOF
+```
+
+Wait for the job to complete:
+
+`kubectl wait --for=condition=Complete --timeout=120s job/job1`
+
+Get the logs from the job to verify that it worked:
+
+`kubectl logs job/job1`

example/hello-populator/crd.yaml

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+apiVersion: apiextensions.k8s.io/v1
+kind: CustomResourceDefinition
+metadata:
+  name: hellos.hello.k8s.io
+  annotations:
+    api-approved.kubernetes.io: unapproved
+spec:
+  group: hello.k8s.io
+  names:
+    kind: Hello
+    listKind: HelloList
+    plural: hellos
+    singular: hello
+  scope: Namespaced
+  versions:
+  - name: v1alpha1
+    schema:
+      openAPIV3Schema:
+        description: Hello is a specification for a Hello resource
+        properties:
+          apiVersion:
+            description: 'APIVersion defines the versioned schema of this representation
+              of an object. Servers should convert recognized schemas to the latest
+              internal value, and may reject unrecognized values. More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#resources'
+            type: string
+          kind:
+            description: 'Kind is a string value representing the REST resource this
+              object represents. Servers may infer this from the endpoint the client
+              submits requests to. Cannot be updated. In CamelCase. More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#types-kinds'
+            type: string
+          spec:
+            description: HelloSpec is the spec for a Hello resource
+            properties:
+              fileContents:
+                type: string
+              fileName:
+                type: string
+            required:
+            - fileContents
+            - fileName
+            type: object
+        required:
+        - spec
+        type: object
+    served: true
+    storage: true
+status:
+  acceptedNames:
+    kind: ""
+    plural: ""
+  conditions: []
+  storedVersions: []

example/hello-populator/deploy.yaml

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+apiVersion: v1
+kind: Namespace
+metadata:
+  name: hello
+---
+apiVersion: v1
+kind: ServiceAccount
+metadata:
+  name: hello-account
+  namespace: hello
+---
+kind: ClusterRole
+apiVersion: rbac.authorization.k8s.io/v1
+metadata:
+  name: hello-role
+rules:
+  - apiGroups: [""]
+    resources: [persistentvolumes]
+    verbs: [get, list, watch, patch]
+  - apiGroups: [""]
+    resources: [persistentvolumeclaims]
+    verbs: [get, list, watch, patch, create, delete]
+  - apiGroups: [""]
+    resources: [pods]
+    verbs: [get, list, watch, create, delete]
+  - apiGroups: [storage.k8s.io]
+    resources: [storageclasses]
+    verbs: [get, list, watch]
+
+  - apiGroups: [hello.k8s.io]
+    resources: [hellos]
+    verbs: [get, list, watch]
+---
+kind: ClusterRoleBinding
+apiVersion: rbac.authorization.k8s.io/v1
+metadata:
+  name: hello-binding
+subjects:
+  - kind: ServiceAccount
+    name: hello-account
+    namespace: hello
+roleRef:
+  kind: ClusterRole
+  name: hello-role
+  apiGroup: rbac.authorization.k8s.io
+---
+kind: Deployment
+apiVersion: apps/v1
+metadata:
+  name: hello-populator
+  namespace: hello
+spec:
+  selector:
+    matchLabels:
+      app: hello
+  template:
+    metadata:
+      labels:
+        app: hello
+    spec:
+      serviceAccount: hello-account
+      containers:
+        - name: hello
+          image: hello-populator:latest
+          imagePullPolicy: IfNotPresent
+          args:
+            - --mode=controller
+            - --image-name=hello-populator:latest
+---
+kind: VolumePopulator
+apiVersion: populator.storage.k8s.io/v1alpha1
+metadata:
+  name: hello-populator
+sourceKind:
+  group: hello.k8s.io
+  kind: Hello

example/hello-populator/go.mod

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+module github.com/kubernetes-csi/lib-volume-populator/example/hello-populator
+
+go 1.15
+
+require (
+	github.com/kubernetes-csi/lib-volume-populator v0.0.0
+	k8s.io/apimachinery v0.19.9
+	k8s.io/klog/v2 v2.8.0
+)
+
+replace github.com/kubernetes-csi/lib-volume-populator => ../..