Kubernetes: Flask with redis

Flask with redis

In Docker Compose: Flask with Redis we have created two dockers that can communicate with each others using docker-compose. The same can be easily achieved with kubernetes. We will do this using declarative style with yaml files. Please refer to Kubernetes: Namespace and Replication Controller.

We have also modified the code of the app. You can find everything in https://github.com/sbartek/sample_flask_with_redis.

Namespace

Let’s start with declaring namespace. Let’s create app.yaml.

apiVersion: v1
kind: Namespace
metadata:
  name: flaskapp-dev

Flask app

Then let’s declare how to create docker with flask using ReplicaSet which is very similar to ReplicationController described in Kubernetes: Namespace and Replication Controller. The only difference in definition of selector. This is done in the following flaskapp-rs.yaml file:

apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: flaskapp
  namespace: flaskapp-dev
spec:
  replicas: 2
  selector:
    matchLabels:
      app: flask
  template:
    metadata:
      labels:
        app: flask
    spec:
      containers:
      - name: flaskapp
        image: barteks/flaskappforredis:latest
        ports:
        - name: http
          containerPort: 80

Flask app service (load balancer)

Next we define a service for serving the flask app. This is done in flaskapp-svc.yaml:

apiVersion: v1
kind: Service
metadata:
  labels:
    app: flask
  name: flaskapp
  namespace: flaskapp-dev
spec:
  ports:
  - name: http
    port: 8080
    targetPort: http
  selector:
    app: flask
  type: LoadBalancer

Redis

redis-rs.yaml:

apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: redis
  namespace: flaskapp-dev
spec:
  replicas: 1
  selector:
    matchLabels:
      app: redis
  template:
    metadata:
      labels:
        app: redis
    spec:
      containers:
      - name: redis
        image: barteks/redis:latest
        ports:
        - name: redisport
          containerPort: 6379

Service for redis

redis-svc.yaml

apiVersion: v1
kind: Service
metadata:
  labels:
    app: redis
  name: redis
  namespace: flaskapp-dev
spec:
  ports:
  - name: redis
    port: 6379
    targetPort: redisport
  selector:
    app: redis

Apply it

kubectl apply -f app-ns.yaml
kubectl apply -f flaskapp-svc.yaml
kubectl apply -f flaskapp-rs.yaml
kubectl apply -f redis-svc.yaml
kubectl apply -f redis-rs.yaml

Updated: 2019-12-29