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MySql Example

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-' to make them distinguishable.
MySQL resources to have 'env: prod' labels so that we can use label selector to query these.
MySQL to use persistent disk for storing data.

Download resources

Download deployment.yaml, service.yaml and secret.yaml. These are plain k8s resources files one could add to a k8s cluster to run MySql.

DEMO_HOME=$HOME/kinflate_demo/mysql
rm -rf $DEMO_HOME && mkdir -p $DEMO_HOME
cd $DEMO_HOME

# Get MySQL configs
for f in service secret deployment ; do \
  wget https://raw.githubusercontent.com/kinflate/mysql/master/emptyDir/$f.yaml ; \
done

Initialize a manifest

A manifest is needed to group these resources together.

Create one:

mkdir -p $DEMO_HOME/prod
cd $DEMO_HOME/prod
kinflate init

You should now have a file called Kube-manifest.yaml:

cat $DEMO_HOME/prod/Kube-manifest.yaml

containing something like:

apiVersion: manifest.k8s.io/v1alpha1
kind: Manifest
metadata:
  name: helloworld
description: helloworld does useful stuff.
namePrefix: some-prefix
# Labels to add to all objects and selectors.
# These labels would also be used to form the selector for apply --prune
# Named differently than “labels” to avoid confusion with metadata for this object
objectLabels:
  app: helloworld
objectAnnotations:
  note: This is a example annotation
resources:
- deployment.yaml
- service.yaml
# There could also be configmaps in Base, which would make these overlays
configmaps: []
# There could be secrets in Base, if just using a fork/rebase workflow
secrets: []
recursive: true

Add resources

Add the resources to the manifest

cd $DEMO_HOME/prod

kinflate add resource ../secret.yaml
kinflate add resource ../service.yaml
kinflate add resource ../deployment.yaml

cat Kube-manifest.yaml

Kube-manifest.yaml's resources section should contain:

apiVersion: manifest.k8s.io/v1alpha1
....
resources:
- ../secret.yaml
- ../service.yaml
- ../deployment.yaml

Now we are ready to apply our first customization.

NamePrefix Customization

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

cd $DEMO_HOME/prod

kinflate set nameprefix 'prod-'

cat Kube-manifest.yaml

Kube-manifest.yaml should have updated value of namePrefix field:

apiVersion: manifest.k8s.io/v1alpha1
....
namePrefix: prod-
objectAnnotations:
 note: This is a example annotation

This namePrefix directive adds prod- to all resource names.

Run kinflate:

cd $DEMO_HOME/prod
kinflate inflate -f .

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/v1beta2
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.

kinflate does not have set label command to add label, but we can edit Kube-manifest.yaml file under prod directory and add the production labels under objectLabels fields as highlighted below.

cd $DEMO_HOME/prod
sed -i 's/app: helloworld/app: prod/' Kube-manifest.yaml

At this point, running kinflate inflate -f . 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. Kinflate lets you apply patches to the resources.

cd $DEMO_HOME/prod

# Create a patch for persistent-disk.yaml
cat <<'EOF' > persistent-disk.yaml
apiVersion: apps/v1beta2 # 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

# Edit the manifest file to add the above patch:
cat <<'EOF' >> $DEMO_HOME/prod/Kube-manifest.yaml
patches:
- persistent-disk.yaml
EOF

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 patches in Kube-manifest.yaml. kinflate inflate 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.

kinflate inflate -f $DEMO_HOME/prod  # | kubectl apply -f -

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