Namespaces¶

Namespaces - Imperative using kubectl
Namespaces - Declarative using YAML & LimitRange
Namespaces - Declarative using YAML & ResourceQuota

Step-01: Kubernetes Namespaces - Imperative using kubectl¶

Namespaces allow to split-up resources into different groups.
Resource names should be unique in a namespace
We can use namespaces to create multiple environments like dev, staging and production etc
Kubernetes will always list the resources from default namespace unless we provide exclusively from which namespace we need information from.

Kubernetes Manifests¶

0102030405060708

#01-storage-class.yml
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata: 
  name: ebs-sc
provisioner: ebs.csi.aws.com
volumeBindingMode: WaitForFirstConsumer

#02-persistent-volume-claim.yml
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: ebs-mysql-pv-claim
spec: 
  accessModes:
    - ReadWriteOnce
  storageClassName: ebs-sc
  resources: 
    requests:
      storage: 4Gi

#03-UserManagement-ConfigMap.yml
apiVersion: v1
kind: ConfigMap
metadata:
  name: usermanagement-dbcreation-script
data: 
  mysql_usermgmt.sql: |-
    DROP DATABASE IF EXISTS usermgmt;
    CREATE DATABASE usermgmt;

#04-mysql-deployment.yml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: mysql
spec: 
  replicas: 1
  selector:
    matchLabels:
      app: mysql
  strategy:
    type: Recreate 
  template: 
    metadata: 
      labels: 
        app: mysql
    spec: 
      containers:
        - name: mysql
          image: mysql:5.6
          env:
            - name: MYSQL_ROOT_PASSWORD
              valueFrom:
                secretKeyRef:
                  name: mysql-db-password
                  key: db-password 
          ports:
            - containerPort: 3306
              name: mysql    
          volumeMounts:
            - name: mysql-persistent-storage
              mountPath: /var/lib/mysql    
            - name: usermanagement-dbcreation-script
              mountPath: /docker-entrypoint-initdb.d #https://hub.docker.com/_/mysql Refer Initializing a fresh instance                                            
      volumes: 
        - name: mysql-persistent-storage
          persistentVolumeClaim:
            claimName: ebs-mysql-pv-claim
        - name: usermanagement-dbcreation-script
          configMap:
            name: usermanagement-dbcreation-script

#05-mysql-clusterip-service.yml
apiVersion: v1
kind: Service
metadata: 
  name: mysql
spec:
  selector:
    app: mysql 
  ports: 
    - port: 3306  
  clusterIP: None # This means we are going to use Pod IP

#06-UserManagementMicroservice-Deployment-Service.yml
apiVersion: apps/v1
kind: Deployment 
metadata:
  name: usermgmt-microservice
  labels:
    app: usermgmt-restapp
spec:
  replicas: 1
  selector:
    matchLabels:
      app: usermgmt-restapp
  template:  
    metadata:
      labels: 
        app: usermgmt-restapp
    spec:
      initContainers:
        - name: init-db
          image: busybox:1.31
          command: ['sh', '-c', 'echo -e "Checking for the availability of MySQL Server deployment"; while ! nc -z mysql 3306; do sleep 1; printf "-"; done; echo -e "  >> MySQL DB Server has started";']      
      containers:
        - name: usermgmt-restapp
          image: stacksimplify/kube-usermanagement-microservice:1.0.0
          ports: 
            - containerPort: 8095           
          env:
            - name: DB_HOSTNAME
              value: "mysql"            
            - name: DB_PORT
              value: "3306"            
            - name: DB_NAME
              value: "usermgmt"            
            - name: DB_USERNAME
              value: "root"            
            - name: DB_PASSWORD
              valueFrom:
                secretKeyRef:
                  name: mysql-db-password
                  key: db-password           
          livenessProbe:
            exec:
              command: 
                - /bin/sh
                - -c 
                - nc -z localhost 8095
            initialDelaySeconds: 60
            periodSeconds: 10
          readinessProbe:
            httpGet:
              path: /usermgmt/health-status
              port: 8095
            initialDelaySeconds: 60
            periodSeconds: 10

#07-UserManagement-Service.yml
apiVersion: v1
kind: Service
metadata:
  name: usermgmt-restapp-service
  labels: 
    app: usermgmt-restapp
spec:
  type: NodePort
  selector:
    app: usermgmt-restapp
  ports: 
    - port: 8095
      targetPort: 8095
      nodePort: 31231

#08-kubernetes-secrets.yml
apiVersion: v1
kind: Secret
metadata:
  name: mysql-db-password
type: Opaque
data: 
  db-password: ZGJwYXNzd29yZDEx

Step-02: Namespaces Generic - Deploy in Dev1 and Dev2¶

Create Namespace¶

# List Namespaces
kubectl get ns 

# Craete Namespace
kubectl create namespace <namespace-name>
kubectl create namespace dev1
kubectl create namespace dev2

# List Namespaces
kubectl get ns

Comment NodePort in UserMgmt NodePort Service¶

File: 07-UserManagement-Service.yml
Why?:
Whenever we create with same manifests multiple environments like dev1, dev2 with namespaces, we cannot have same worker node port for multiple services.
We will have port conflict.
Its good for k8s system to provide dynamic nodeport for us in such situations.
```
      #nodePort: 31231
```

Error if not commented

The Service "usermgmt-restapp-service" is invalid: spec.ports[0].nodePort: Invalid value: 31231: provided port is already allocated

Deploy All k8s Objects¶

# Deploy All k8s Objects
kubectl apply -f kube-manifests/ -n dev1
kubectl apply -f kube-manifests/ -n dev2

# List all objects from dev1 & dev2 Namespaces
kubectl get all -n dev1
kubectl get all -n dev2

Step-03: Verify SC,PVC and PV¶

Shorter Note
PVC is a namespace specific resource
PV and SC are generic

Observation-1: Persistent Volume Claim (PVC) gets created in respective namespaces

# List PVC for dev1 and dev2
kubectl get pvc -n dev1
kubectl get pvc -n dev2

Observation-2: Storage Class (SC) and Persistent Volume (PV) gets created generic. No specifc namespace for them
```
# List sc,pv
kubect get sc,pv
```

Step-04: Access Application¶

Dev1 Namespace¶

# Get Public IP
kubectl get nodes -o wide

# Get NodePort for dev1 usermgmt service
kubectl get svc -n dev1

# Access Application
http://<Worker-Node-Public-Ip>:<Dev1-NodePort>/usermgmt/health-stauts

Dev2 Namespace¶

# Get Public IP
kubectl get nodes -o wide

# Get NodePort for dev2 usermgmt service
kubectl get svc -n dev2

# Access Application
http://<Worker-Node-Public-Ip>:<Dev2-NodePort>/usermgmt/health-stauts

AWS EKS - Elastic Kubernetes Service - Masterclass¶

Step-05: Clean-Up¶

# Delete namespaces dev1 & dev2
kubectl delete ns dev1
kubectl delete ns dev2

# List all objects from dev1 & dev2 Namespaces
kubectl get all -n dev1
kubectl get all -n dev2

# List Namespaces
kubectl get ns

# List sc,pv
kubectl get sc,pv

# Delete Storage Class
kubectl delete sc ebs-sc

# Get all from All Namespaces
kubectl get all -all-namespaces

References:¶

https://kubernetes.io/docs/tasks/administer-cluster/namespaces-walkthrough/