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Stateless Application Migration with Kustomize

This tutorial shows you how to migrate a simple stateless PHP Guestbook application using Crane Runner, Kustomize, and Tekton ClusterTasks. Unlike, in the previous exercise where the application was mirrored from one namespace in the "source" cluster to the same namespace in the "destination" cluster, here you will use a Kustomize overlay to import the workload into the desired namespace.

If you just completed Stateless Application Mirror, then you can skip to Prepare for Application Migration.

Roadmap

  • Deploy Guestbook application in "source" cluster.
  • Prepare for application migration.
  • Explore new ClusterTasks.
  • Migrate the Guestbook application using kustomize overlay in a Tekton PipelineRun.

Before You Begin

You will need a "source" and "destination" Kubernetes cluster with Tekton and the Crane Runner ClusterTasks installed. Below are the steps required for easy copy/paste:

# Start up "source" and "destination" clusters in minikube
wget "https://raw.githubusercontent.com/konveyor/crane/main/hack/minikube-clusters-start.sh"
chmod +x minikube-clusters-start.sh
./minikube-clusters-start.sh

# Install Tekton
# See https://tekton.dev/docs/getting-started/ for help with installing Tekton
kubectl --context dest apply -f "https://storage.googleapis.com/tekton-releases/pipeline/latest/release.yaml"
kubectl --context dest --namespace tekton-pipelines wait --for=condition=ready pod --selector=app.kubernetes.io/component=controller --timeout=180s

# Install Crane Runner manifests
kubectl --context dest apply -k github.com/konveyor/crane-runner/config/default

Deploy Guestbook Application in "source" Cluster

You will be deploying Kubernetes' stateless guestbook application modified here to be consumable via kustomize. The guestbook application consisists of:

  • redis leader deployment and service
  • redis follower deployment and service
  • guestbook front-end deployment and service
kubectl --context src create namespace guestbook
kubectl --context src --namespace guestbook apply -k github.com/konveyor/crane-runner/examples/resources/guestbook
kubectl --context src --namespace guestbook wait --for=condition=ready pod --selector=app=guestbook --timeout=180s

Prepare for Application Migration

First, create the hello-kustomize namespace in the "destination" cluster where you will migrate the guestbook application from the "source" cluster.

kubectl --context dest create namespace hello-kustomize

You must upload your kubeconfig as a secret. This will be used by the ClusterTasks to migrate the application.

kubectl config view --flatten | kubectl --context dest --namespace hello-kustomize create secret generic kubeconfig --from-file=config=/dev/stdin

Explore new ClusterTasks

Create Tekton PipelineRun

Submit the PipelineRun:

kubectl --context dest --namespace hello-kustomize create -f "https://raw.githubusercontent.com/konveyor/crane-runner/main/examples/stateless-app-migration-with-kustomize/pipelinerun.yaml"

You can watch what's happening with:

Every 2.0s: kubectl --context dest --namespace hello-kustomize get pipelineruns,taskruns,pvc,pods

NAME                                           SUCCEEDED   REASON      STARTTIME   COMPLETIONTIME
pipelinerun.tekton.dev/hello-kustomize-2fl82   True        Succeeded   107s        54s

NAME                                                               SUCCEEDED   REASON      STARTTIME   COMPLETIONTIME
taskrun.tekton.dev/hello-kustomize-2fl82-apply                     True        Succeeded   77s         71s
taskrun.tekton.dev/hello-kustomize-2fl82-export                    True        Succeeded   107s        84s
taskrun.tekton.dev/hello-kustomize-2fl82-kubectl-apply-kustomize   True        Succeeded   64s         54s
taskrun.tekton.dev/hello-kustomize-2fl82-kustomize                 True        Succeeded   71s         65s
taskrun.tekton.dev/hello-kustomize-2fl82-transform                 True        Succeeded   84s         77s

NAME                                   STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
persistentvolumeclaim/pvc-f8438cd335   Bound    pvc-ab83ac0d-52f1-4f0f-b244-77bf34bcdedb   10Mi       RWO            standard       107s

NAME                                                    READY   STATUS      RESTARTS   AGE
pod/frontend-5fd859dcf6-hhfgs                           1/1     Running     0          57s
pod/frontend-5fd859dcf6-p7qsk                           1/1     Running     0          57s
pod/frontend-5fd859dcf6-szkw6                           1/1     Running     0          57s
pod/hello-kustomize-2fl82-apply-pod                     0/1     Completed   0          77s
pod/hello-kustomize-2fl82-export-pod                    0/1     Completed   0          107s
pod/hello-kustomize-2fl82-kubectl-apply-kustomize-pod   0/1     Completed   0          64s
pod/hello-kustomize-2fl82-kustomize-pod                 0/1     Completed   0          71s
pod/hello-kustomize-2fl82-transform-pod                 0/1     Completed   0          84s
pod/redis-master-55d9747c6c-84p8s                       1/1     Running     0          57s
pod/redis-slave-5c6b4c5b47-cslpt                        1/1     Running     0          57s
pod/redis-slave-5c6b4c5b47-mjslc                        1/1     Running     0          57s

A few things for you to note when looking at the PipelineRun:

  • Data is shared between the tasks using a volumeClaimTemplate. Used in this way, it lives as long as the PipelineRun.
  • All but the first task use runAfter to make the Tasks run sequentially.

Verify the Migrated Application is Healthy

You can check that everything survived the move:

kubectl --context dest --namespace hello-kustomize get all

Then, verify the Guestbook application's frontend is running properly:

kubectl --context dest --namespace hello-kustomize port-forward svc/frontend 8080:80

Then navigate to localhost:8080 from your browser.

What's Next

Cleanup

kubectl --context dest delete namespace hello-kustomize