README.md

Demo: MySql

This example takes some off-the-shelf k8s resources designed for MySQL, and customizes them to suit a production scenario.

In the production environment we want:

• MySQL resource names to be prefixed by 'prod-'.
• MySQL resources to have 'env: prod' labels.
• MySQL to use persistent disk for storing data.

First make a place to work:

DEMO_HOME=$(mktemp -d)

Download resources

To keep this document shorter, the base resources needed to run MySql on a k8s cluster are off in a supplemental data directory rather than declared here as HERE documents.

Download them:

curl -s  -o "$DEMO_HOME/#1.yaml" "https://raw.githubusercontent.com\
/kubernetes-sigs/kustomize\
/master/examples/mySql\
/{deployment,secret,service}.yaml"

Initialize kustomization.yaml

The kustomize program gets its instructions from a file called kustomization.yaml.

Start this file:

touch $DEMO_HOME/kustomization.yaml

Add the resources

cd $DEMO_HOME

kustomize edit add resource secret.yaml
kustomize edit add resource service.yaml
kustomize edit add resource deployment.yaml

cat kustomization.yaml

kustomization.yaml's resources section should contain:

resources:
- secret.yaml
- service.yaml
- deployment.yaml

Name Customization

Arrange for the MySQL resources to begin with prefix prod- (since they are meant for the production environment):

cd $DEMO_HOME

kustomize edit set nameprefix 'prod-'

cat kustomization.yaml

kustomization.yaml should have updated value of namePrefix field:

namePrefix: prod-

This namePrefix directive adds prod- to all resource names.

kustomize build $DEMO_HOME

The output should contain:

apiVersion: v1
data:
  password: YWRtaW4=
kind: Secret
metadata:
  ....
  name: prod-mysql-pass-d2gtcm2t2k
---
apiVersion: v1
kind: Service
metadata:
  ....
  name: prod-mysql
spec:
  ....
---
apiVersion: apps/v1
kind: Deployment
metadata:
  ....
  name: prod-mysql
spec:
  selector:
    ....

Label Customization

We want resources in production environment to have certain labels so that we can query them by label selector.

kustomize does not have edit set label command to add a label, but one can always edit kustomization.yaml directly:

sed -i.bak 's/app: helloworld/app: prod/' \
    $DEMO_HOME/kustomization.yaml

At this point, running kustomize build will generate MySQL configs with name-prefix 'prod-' and labels env:prod.

Storage customization

Off the shelf MySQL uses emptyDir type volume, which gets wiped away if the MySQL Pod is recreated, and that is certainly not desirable for production environment. So we want to use Persistent Disk in production. kustomize lets you apply patchesStrategicMerge to the resources.

cat <<'EOF' > $DEMO_HOME/persistent-disk.yaml
apiVersion: apps/v1 # for versions before 1.9.0 use apps/v1beta2
kind: Deployment
metadata:
  name: mysql
spec:
  template:
    spec:
      volumes:
      - name: mysql-persistent-storage
        emptyDir: null
        gcePersistentDisk:
          pdName: mysql-persistent-storage
EOF

Add the patch file to kustomization.yaml:

cat <<'EOF' >> $DEMO_HOME/kustomization.yaml
patchesStrategicMerge:
- persistent-disk.yaml
EOF

A mysql-persistent-storage persistent disk needs to exist for it to run successfully.

Lets break this down:

• In the first step, we created a YAML file named persistent-disk.yaml to patch the resource defined in deployment.yaml

• Then we added persistent-disk.yaml to list of patchesStrategicMerge in kustomization.yaml. kustomize build will apply this patch to the deployment resource with the name mysql as defined in the patch.

The output of the following command can now be applied to the cluster (i.e. piped to kubectl apply) to create the production environment.

kustomize build $DEMO_HOME  # | kubectl apply -f -