ratings-service

A small base for potential talk @ Java2Days 2019

How to run your service locally in Kubernetes.

Install and configure
Build docker image
Deploy mysql
Deploy your service
- Deploy your backend service
- Create a service to make the service visible
Scale
Undo deployment
Stop
Delete

Minikube install and configure

Usually for this purpose is used Minikube. Minikube is a tool that makes it easy to run Kubernetes locally.

[Install Minikube] (https://kubernetes.io/docs/tasks/tools/install-minikube/)

Minikube runs a single-node Kubernetes cluster inside a Virtual Machine (VM).

Also will install kubectl which is client which will communicate with API server running on cluster master node.

Start Minikube and create a cluster:

minikube start

Reuse the docker daemon locally:

eval $(minikube docker-env)

Configure kubectl to use the context minikube: kubectl config use-context minikube

A context is a group of access parameters: cluster, a user, and a namespace.

2. Build a docker image of the backend service:

docker build -t ratings-service -f deployment/Dockerfile .

Mysql configure and deploy.

In order to connect to mysql we need configurations like: host, port, user, pass

Kubernetes object ConfigMaps allow you to decouple configuration artifacts from image content to keep containerized applications portable.

Example ConfigMaps for our mysql in file minikube-config.yaml:

apiVersion: v1
kind: ConfigMap
metadata:
  name: ratings-config
data:
  mysql.host: "mysql-service"
  mysql.port: "3306"
  mysql.user: "root"

Apply the configuration in minikube kubectl apply -f minikube-config.yaml

Kubernetes secret objects let you store and manage sensitive information, such as passwords.

Create the file minikube-credentials.yaml:

apiVersion: v1
kind: Secret
metadata:
  name: mysql-credentials
type: Opaque
data:
  # base 64 encoded
  password: dG9wc2VjcmV0

Apply the password configuration: kubectl apply -f minikube-credentials.yaml

Where is our Data?

A PersistentVolume (PV) is a piece of storage in the cluster that has been provisioned by an administrator or dynamically provisioned using Storage Classes.

minikube-mysql-pv.yaml

apiVersion: v1
kind: PersistentVolume
metadata:
  name: mysql-pv-volume
spec:
  accessModes:
    - ReadWriteOnce
  capacity:
    storage: 1Gi
  hostPath:
    path: /tmp/data
  persistentVolumeReclaimPolicy: Retain
  storageClassName: manual
  volumeMode: Filesystem

Apply the PV: kubectl apply -f minikube-mysql-pv.yaml

A PersistentVolumeClaim (PVC) is a request for storage by a user. It is similar to a Pod. Pods consume node resources and PVCs consume PV resources.

minikube-mysql-pvc.yaml

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mysql-pv-claim
spec:
  storageClassName: manual
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 1Gi

Apply the PVC: kubectl apply -f minikube-mysql-pvc.yaml

Create a service

apiVersion: v1
kind: Service
metadata:
  name: mysql-service
spec:
  ports:
    - port: 3306
  selector:
    app: mysql
  clusterIP: None

Apply service: kubectl apply -f minikube-mysql-service.yaml

Service deployment:

spec:
  selector:
    matchLabels:
      app: mysql
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: mysql
    spec:
      containers:
        - image: mysql:5.6
          name: mysql
          env:
            - name: MYSQL_ROOT_PASSWORD
              valueFrom:
                secretKeyRef:
                  name: mysql-credentials
                  key: password
          ports:
            - containerPort: 3306
              name: mysql
          volumeMounts:
            - name: mysql-persistent-storage
              mountPath: /var/lib/mysql
      volumes:
        - name: mysql-persistent-storage
          persistentVolumeClaim:
            claimName: mysql-pv-claim

Deploy ratings-service: kubectl apply -f minikube-mysql-deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: ratings-backend
spec:
  replicas: 1
  selector:
    matchLabels:
      app: ratings-backend
  template:
    metadata:
      labels:
        app: ratings-backend
      annotations:
        balev.eu/author: "Lachezar Balev"
    spec:
      containers:
        - name: ratings-backend
          image: luchob/ratings-service:latest
          imagePullPolicy: Never
          ports:
            - containerPort: 8080
              name: server-port
          env:
            - name: MYSQL_HOST
              valueFrom:
                configMapKeyRef:
                  name: ratings-config
                  key: mysql.host
            - name: MYSQL_PORT
              valueFrom:
                configMapKeyRef:
                  name: ratings-config
                  key: mysql.port
            - name: MYSQL_USER
              valueFrom:
                configMapKeyRef:
                  name: ratings-config
                  key: mysql.user
            - name: MYSQL_PASSWORD
              valueFrom:
                secretKeyRef:
                  name: mysql-credentials
                  key: password

kubectl apply -f minikube-backend.yaml

kubectl apply -f minikube-backend-service.yaml