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Amit Kumar Das
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chore(examples): add genericcontroller based helloworld controller (#118)
Signed-off-by: AmitKumarDas <amit.das@mayadata.io>
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‎examples/gctl/hello-world/.gitignore‎

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/vendor/

‎examples/gctl/hello-world/Dockerfile‎

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# --------------------------
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# Build d-operators binary
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# --------------------------
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FROM golang:1.13.5 as builder
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WORKDIR /example.io/hello-world/
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# copy go modules manifests
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COPY go.mod go.mod
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COPY go.sum go.sum
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COPY Makefile Makefile
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COPY vendor/ vendor/
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# ensure vendoring is up-to-date by running make vendor
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# in your local setup
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#
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# we cache the vendored dependencies before building and
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# copying source so that we don't need to re-download when
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# source changes don't invalidate our downloaded layer
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RUN go mod download
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RUN go mod tidy
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RUN go mod vendor
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# copy source file(s)
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COPY cmd/ cmd/
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# build the binary
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RUN make
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# ---------------------------
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# Use distroless as minimal base image to package the final binary
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# Refer https://github.com/GoogleContainerTools/distroless
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# ---------------------------
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FROM gcr.io/distroless/static:nonroot
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WORKDIR /
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COPY --from=builder /example.io/hello-world/hello-world .
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COPY config/config.yaml /etc/config/metac/
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USER nonroot:nonroot
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CMD ["/hello-world"]

‎examples/gctl/hello-world/Makefile‎

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ALL_SRC = $(shell find . -name "*.go" | grep -v -e "vendor")
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IMG_NAME ?= hello-world
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PACKAGE_VERSION ?= latest
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all: bins
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bins: vendor $(IMG_NAME)
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$(IMG_NAME): $(ALL_SRC)
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@echo "+ Generating $(IMG_NAME) binary"
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@CGO_ENABLED=0 GOOS=linux GOARCH=amd64 GO111MODULE=on \
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go build -o $@ ./cmd/main.go
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$(ALL_SRC): ;
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# go mod download modules to local cache
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# make vendored copy of dependencies
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# install other go binaries for code generation
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.PHONY: vendor
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vendor: go.mod go.sum
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@GO111MODULE=on go mod download
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@GO111MODULE=on go mod tidy
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@GO111MODULE=on go mod vendor
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.PHONY: image
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image:
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docker build -t $(IMG_NAME):$(PACKAGE_VERSION) .

‎examples/gctl/hello-world/README.md‎

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## Hello World K8s controller
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- This is a K8s controller that imports metac as library
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- In other words, this uses inline hooks than webhooks
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- Controller's K8s dependencies is configured in a config file
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- Refer: config/config.yaml
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- Controller business logic is implemented in Go
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- Refer: cmd/main.go
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- K8s is completely abstracted from this logic
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- Logic is implemented in respective reconcile functions
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- A Pod gets created via sync inline hook
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- This Pod gets deleted via finalize inline hook
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- Docker image includes the binary as well as its config file
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- Refer: Dockerfile
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- Controller is deployed as a single StatefulSet
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- No need of separate metac binary since metac is used as a library
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- Refer: helloworld-operator.yaml
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### Steps
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```sh
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# workstation needs to have Docker
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# use kind to create a k8s cluster
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#
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# Refer: https://kind.sigs.k8s.io/docs/user/local-registry/
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sudo ./kind-with-registry.sh
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# cat $HOME/.kube/config
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# connect to kind cluster
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sudo kubectl cluster-info --context kind-kind
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# debugging info if required
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#
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# Kubernetes master is running at https://127.0.0.1:32774
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#
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# KubeDNS is running at:
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# https://127.0.0.1:32774/api/v1/namespaces/# kube-system/services/kube-dns:dns/proxy
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#
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# To further debug and diagnose cluster problems, use
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#'kubectl cluster-info dump'.
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```
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```sh
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# workstation needs to have Docker
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make image
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# tag the image to use the local registry
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sudo docker tag hello-world:latest localhost:5000/hello-world:latest
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# push to local registry configured to be used by kind
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sudo docker push localhost:5000/hello-world:latest
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```
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```sh
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# install namespace, rbac, crds & operator
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sudo kubectl apply -f helloworld-ns.yaml
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sudo kubectl apply -f helloworld-rbac-crd.yaml
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sudo kubectl apply -f helloworld-operator.yaml
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# verify if above were installed properly
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sudo kubectl get ns
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sudo kubectl get crd
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sudo kubectl get sts -n hello-world
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sudo kubectl describe po -n hello-world
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sudo kubectl get po -n hello-world
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sudo kubectl logs -n hello-world hello-world-0
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```
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### Test
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```sh
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# create the helloworld custom resource
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sudo kubectl apply -f helloworld.yaml
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# verify creation of Pod
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sudo kubectl get pods -n hello-world
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# delete helloworld custom resource
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sudo kubectl delete -f helloworld.yaml
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# verify deletion of Pod
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sudo kubectl get pods -n hello-world
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# verify deletion of helloworld
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sudo kubectl get helloworlds -n hello-world
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```
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### Cleanup
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```sh
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sudo kubectl delete -f helloworld-operator.yaml
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sudo kubectl delete -f helloworld-rbac-crd.yaml
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sudo kubectl delete -f helloworld-ns.yaml
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sudo kind delete cluster
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```

‎examples/gctl/hello-world/cmd/main.go‎

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package main
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import (
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"fmt"
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"github.com/golang/glog"
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"github.com/pkg/errors"
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"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
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"openebs.io/metac/controller/generic"
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"openebs.io/metac/start"
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)
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// sync executes the reconciliation logic for the watched resource.
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// In this case resource under watch is a custom resource with kind
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// Helloworld.
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//
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// NOTE:
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// SyncHookRequest is the payload received as part of reconcile
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// request. Similarly, SyncHookResponse is the payload sent as a
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// response as part of reconcile request.
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//
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// NOTE:
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// SyncHookRequest has the resource that is under watch (here
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// Helloworld custom resource)
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//
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// NOTE:
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// Both SyncHookRequest & SyncHookResponse have the resources that
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// form the desired state w.r.t the watched resource. These desired
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// resources are termed as attachments by metac. SyncHookRequest has
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// these attachments filled up by metac based on what is observed
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// in the k8s cluster. SyncHookResponse's attachments needs to be
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// filled up with what is desired by this controller logic.
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func sync(
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request *generic.SyncHookRequest,
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response *generic.SyncHookResponse,
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) error {
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glog.Infof("Starting hello world sync")
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defer glog.Infof("Completed hello world sync")
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// extract spec.who from Helloworld
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who, found, err := unstructured.NestedString(
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request.Watch.UnstructuredContent(),
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"spec",
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"who",
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)
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if err != nil {
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return err
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}
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if !found {
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return errors.Errorf("Can't sync: spec.who is not set")
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}
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// build the desired Pod
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desired := &unstructured.Unstructured{
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Object: map[string]interface{}{
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"kind": "Pod",
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"apiVersion": "v1",
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"metadata": map[string]interface{}{
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"name": request.Watch.GetName(),
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"namespace": request.Watch.GetNamespace(),
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"annotations": map[string]interface{}{
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// this annotation helps in associating the watch
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// with its corresponding attachment
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"helloworld/uid": string(request.Watch.GetUID()),
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},
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},
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"spec": map[string]interface{}{
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"restartPolicy": "OnFailure",
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"containers": []interface{}{
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map[string]interface{}{
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"name": "hello",
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"image": "busybox",
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"command": []interface{}{
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"echo",
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fmt.Sprintf("Hello, %s", who),
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},
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},
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},
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},
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},
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}
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// add this desired Pod instance to response
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// to let metac create this in the k8s cluster
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response.Attachments = append(
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response.Attachments,
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desired,
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)
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return nil
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}
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// finalize will delete the attachment(s) created during
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// reconciliation of the watch
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//
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// NOTE:
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// Presence of finalize in the config automatically adds
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// finalizers against the watch
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//
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// NOTE:
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// Once attachments are deleted from the cluster,
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// 'response.Finalized' is set to true which in turn removes
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// this finalizers from the watch
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func finalize(
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request *generic.SyncHookRequest,
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response *generic.SyncHookResponse,
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) error {
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glog.Infof("Starting hello world finalize")
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defer glog.Infof("Completed hello world finalize")
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if request.Attachments.IsEmpty() {
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response.Finalized = true
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}
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return nil
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}
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func main() {
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generic.AddToInlineRegistry("sync/helloworld", sync)
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generic.AddToInlineRegistry("finalize/helloworld", finalize)
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start.Start()
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}

‎examples/gctl/hello-world/config/config.yaml‎

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apiVersion: metac.openebs.io/v1alpha1
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kind: GenericController
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metadata:
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name: hello-world-controller
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spec:
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watch:
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apiVersion: example.com/v1
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resource: helloworlds
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attachments:
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- apiVersion: v1
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resource: pods
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updateStrategy:
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method: Recreate
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advancedSelector:
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selectorTerms:
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- matchReferenceExpressions:
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# select Pod if its annotation
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#
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# matches HelloWorld _(i.e. watch)_ UID
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- key: metadata.annotations.helloworld/uid
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operator: EqualsWatchUID
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hooks:
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sync:
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inline:
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funcName: sync/helloworld
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finalize:
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inline:
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funcName: finalize/helloworld

‎examples/gctl/hello-world/go.mod‎

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module example.io/hello-world
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go 1.13
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require (
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github.com/coreos/etcd v3.3.15+incompatible // indirect
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github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b
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github.com/pkg/errors v0.9.1
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golang.org/x/sys v0.0.0-20200113162924-86b910548bc1 // indirect
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k8s.io/apimachinery v0.17.3
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k8s.io/client-go v0.17.3 // indirect
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openebs.io/metac v0.2.1
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)
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replace (
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k8s.io/apimachinery => k8s.io/apimachinery v0.17.3
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k8s.io/client-go => k8s.io/client-go v0.17.3
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openebs.io/metac => github.com/AmitKumarDas/metac v0.2.1
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)

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