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Demo: LDAP with variants

Steps:

  1. Clone an existing configuration as a base.
  2. Customize it.
  3. Create two different overlays (staging and production) from the customized base.
  4. Run kustomize and kubectl to deploy staging and production.

First define a place to work:

DEMO_HOME=$(mktemp -d)

Alternatively, use

DEMO_HOME=~/ldap

Establish the base

To use overlays to create variants, we must first establish a common base.

To keep this document shorter, the base resources are off in a supplemental data directory rather than declared here as HERE documents. Download them:

BASE=$DEMO_HOME/base
mkdir -p $BASE

CONTENT="https://raw.githubusercontent.com\
/kubernetes-sigs/kustomize\
/master/examples/ldap"

curl -s -o "$BASE/#1" "$CONTENT/base\
/{deployment.yaml,kustomization.yaml,service.yaml,env.startup.txt}"

Look at the directory:

tree $DEMO_HOME

Expect something like:

/tmp/tmp.IyYQQlHaJP
└── base
    ├── deployment.yaml
    ├── env.startup.txt
    ├── kustomization.yaml
    └── service.yaml

One could immediately apply these resources to a cluster:

kubectl apply -f $DEMO_HOME/base

to instantiate the ldap service. kubectl would only recognize the resource files.

The Base Kustomization

The base directory has a kustomization file:

more $BASE/kustomization.yaml

Optionally, run kustomize on the base to emit customized resources to stdout:

kustomize build $BASE

Customize the base

A first customization step could be to set the name prefix to all resources:

cd $BASE
kustomize edit set nameprefix "my-"

See the effect:

kustomize build $BASE | grep -C 3 "my-"

Create Overlays

Create a staging and production overlay:

  • Staging adds a configMap.
  • Production has a higher replica count and a persistent disk.
  • variants will differ from each other.
OVERLAYS=$DEMO_HOME/overlays
mkdir -p $OVERLAYS/staging
mkdir -p $OVERLAYS/production

Staging Kustomization

Download the staging customization and patch.

curl -s -o "$OVERLAYS/staging/#1" "$CONTENT/overlays/staging\
/{config.env,deployment.yaml,kustomization.yaml}"

The staging customization adds a configMap.

(...truncated)
configMapGenerator:
  - name: env-config
    files:
      - config.env

as well as 2 replica

apiVersion: apps/v1
kind: Deployment
metadata:
  name: ldap
spec:
  replicas: 2

Production Kustomization

Download the production customization and patch.

curl -s -o "$OVERLAYS/production/#1" "$CONTENT/overlays/production\
/{deployment.yaml,kustomization.yaml}"

The production customization adds 6 replica as well as a consistent disk.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: ldap
spec:
  replicas: 6
  template:
    spec:
      volumes:
        - name: ldap-data
          emptyDir: null
          gcePersistentDisk:
            pdName: ldap-persistent-storage

Compare overlays

DEMO_HOME now contains:

  • a base directory - a slightly customized clone of the original configuration, and

  • an overlays directory, containing the kustomizations and patches required to create distinct staging and production variants in a cluster.

Review the directory structure and differences:

tree $DEMO_HOME

Expecting something like:

/tmp/tmp.IyYQQlHaJP1
├── base
│   ├── deployment.yaml
│   ├── env.startup.txt
│   ├── kustomization.yaml
│   └── service.yaml
└── overlays
    ├── production
    │   ├── deployment.yaml
    │   └── kustomization.yaml
    └── staging
        ├── config.env
        ├── deployment.yaml
        └── kustomization.yaml

Compare the output directly to see how staging and production differ:

diff \
  <(kustomize build $OVERLAYS/staging) \
  <(kustomize build $OVERLAYS/production) |\
  more

The difference output should look something like

(...truncated)
<   name: staging-my-ldap-configmap-kftftt474h
---
>   name: production-my-ldap-configmap-k27f7hkg4f
85c75
<   name: staging-my-ldap-service
---
>   name: production-my-ldap-service
97c87
<   name: staging-my-ldap
---
>   name: production-my-ldap
99c89
<   replicas: 2
---
>   replicas: 6
(...truncated)

Deploy

The individual resource sets are:

kustomize build $OVERLAYS/staging

kustomize build $OVERLAYS/production

To deploy, pipe the above commands to kubectl apply:

kustomize build $OVERLAYS/staging |\
    kubectl apply -f -

kustomize build $OVERLAYS/production |\
   kubectl apply -f -