Demo: hello app

This demo helps you to deploy an example hello app end-to-end using kustomize.

Steps:

Create the resources files.
Kustomize them.
Spin-up kubernetes cluster on local using kind.
Deploy the app using kustomize and verify the status.

First define a place to work:

DEMO_HOME=$(mktemp -d)

Alternatively, use

DEMO_HOME=~/hello

Establish the base

Let's run the hello service.

BASE=$DEMO_HOME/base
mkdir -p $BASE
OUTPUT=$DEMO_HOME/output
mkdir -p $OUTPUT

Now lets add a simple config map resource to the base

cat <<EOF >$BASE/configMap.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: the-map
data:
  altGreeting: "Good Morning!"
  enableRisky: "false"
EOF

Create deployment.yaml with any image and with desired number of replicas

cat <<EOF >$BASE/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: the-deployment
spec:
  replicas: 3
  template:
    metadata:
      labels:
        deployment: hello
    spec:
      containers:
      - name: the-container
        image: monopole/hello:1
        command: ["/hello",
                  "--port=8080",
                  "--enableRiskyFeature=\$(ENABLE_RISKY)"]
        ports:
        - containerPort: 8080
        env:
        - name: ALT_GREETING
          valueFrom:
            configMapKeyRef:
              name: the-map
              key: altGreeting
        - name: ENABLE_RISKY
          valueFrom:
            configMapKeyRef:
              name: the-map
              key: enableRisky
EOF

Create service.yaml pointing to the deployment created above

cat <<EOF >$BASE/service.yaml
kind: Service
apiVersion: v1
metadata:
  name: the-service
spec:
  selector:
    deployment: hello
  type: LoadBalancer
  ports:
  - protocol: TCP
    port: 8666
    targetPort: 8080
EOF

Create a grouping.yaml resource. By this, you are defining the grouping of the current directory, base. Kustomize uses the unique label in this file to track any future state changes made to this directory. Make sure the label key is kustomize.config.k8s.io/inventory-id and give any unique label value and DO NOT change it in future.

cat <<EOF >$BASE/grouping.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: inventory-map
  labels:
    kustomize.config.k8s.io/inventory-id: hello-app
EOF

Now, create kustomization.yaml add all your resources.

cat <<EOF >$BASE/kustomization.yaml
commonLabels:
  app: hello

resources:
- deployment.yaml
- service.yaml
- configMap.yaml
- grouping.yaml
EOF

The Base Kustomization

The base directory has a kustomization file:

more $BASE/kustomization.yaml

Customize the base

A simple customization step could be to change the app label applied to all resources:

sed -i.bak 's/app: hello/app: my-hello/' \
    $BASE/kustomization.yaml

The following requires installation of kind.

Delete any existing kind cluster and create a new one. By default the name of the cluster is "kind"

kind delete cluster
kind create cluster

Use the kustomize binary in MYGOBIN to apply a deployment, fetch the status and verify the status.

export KUSTOMIZE_ENABLE_ALPHA_COMMANDS=true

kustomize resources apply $BASE --status;

kustomize status fetch $BASE > $OUTPUT/status

test 1 == \
  $(grep "the-deployment" $OUTPUT/status | grep "Deployment is available. Replicas: 3" | wc -l); \
  echo $?

test 1 == \
  $(grep "the-map" $OUTPUT/status | grep "Resource is always ready" | wc -l); \
  echo $?

test 1 == \
  $(grep "the-service" $OUTPUT/status | grep "Service is ready" | wc -l); \
  echo $?

Now let's replace the configMap with configMap2 apply the config, fetch and verify the status. This should delete the-map from deployment and add the-map2.

cat <<EOF >$BASE/configMap2.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: the-map2
data:
  altGreeting: "Good Evening!"
  enableRisky: "false"
EOF

rm $BASE/configMap.yaml

sed -i.bak 's/configMap/configMap2/' \
    $BASE/kustomization.yaml

sed -i.bak 's/the-map/the-map2/' \
    $BASE/deployment.yaml

kustomize resources apply $BASE --status;

status=$(mktemp);
kustomize status fetch $BASE > $OUTPUT/status

test 1 == \
  $(grep "the-deployment" $OUTPUT/status | grep "Deployment is available. Replicas: 3" | wc -l); \
  echo $?

test 1 == \
  $(grep "the-map2" $OUTPUT/status | grep "Resource is always ready" | wc -l); \
  echo $?

test 1 == \
  $(grep "the-service" $OUTPUT/status | grep "Service is ready" | wc -l); \
  echo $?

Clean-up the cluster

kind delete cluster

Next Exercise

Create overlays as described in the helloWorld section and verify the results.