06-run-simple-application-in-kubernetes

Deploy Simple Application in Kubernetes

Diagram

Application

Kubernetes Objects

Create MySQL (Deployment and Service) in database namespace

Notice: StatefulSet is more preferable resource to manage database applications, but just for simplicity Deployment is used for MySQL here.

1. Create database namespace.

   kubectl create namespace database
   

   • Check your namespace exists

     kubectl get ns database
     NAME       STATUS   AGE
     database   Active   9s
     

2. Create Deployment for MySQL.

   kubectl apply -f mysql-deployment.yaml -n database
   

   how to create the yaml easily

   Create base yaml file:

   kubectl create deploy mysql --image=mysql:8 --dry-run=client -o yaml > mysql-deployment.yaml
   

   Add required env:

       env:
         - name: MYSQL_ROOT_PASSWORD
           value: password
         - name: MYSQL_DATABASE
           value: test_db
         - name: MYSQL_USER
           value: sample_app
         - name: MYSQL_PASSWORD
           value: password

   • Check Deployment in database Namespace

     kubectl get deploy -n database
     

   • Check ReplicaSet in database Namespace

     kubectl describe replicaset -n database
     

     result

       ...
       Controlled By:  Deployment/mysql
       ...
     

   • Check Pod in database Namespace

     kubectl get pods -n database
     

   • Check if you can connect to MySQL with kubectl exec

     kubectl exec -n database -it $(kubectl get po -n database | grep mysql | head -1 | awk '{print $1}') -- mysql -uroot -ppassword
     

     result

     mysql: [Warning] Using a password on the command line interface can be insecure.
     Welcome to the MySQL monitor.  Commands end with ; or \g.
     Your MySQL connection id is 8
     Server version: 8.0.31 MySQL Community Server - GPL
     
     Copyright (c) 2000, 2022, Oracle and/or its affiliates.
     
     Oracle is a registered trademark of Oracle Corporation and/or its
     affiliates. Other names may be trademarks of their respective
     owners.
     
     Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
     
     mysql>

3. Create Service for MySQL.

   1. Create Service.

      kubectl create -f mysql-service.yaml -n database
      

      how to create the yaml easily

      kubectl create service clusterip mysql --tcp=3306 --dry-run=client --output yaml > mysql-service.yaml
      

      • Check the created Service

        kubectl get service -n database
        

Create sample application (Deployment, ConfigMap, Secret, and Service) in your namespace

Sample application: https://github.com/nakamasato/fastapi-sample

1. Set your name to namespace variable.

   namespace=<yourname>
   

2. Create your namespace.

   kubectl create namespace $namespace
   

   • Check your namespace exists

     kubectl get ns $namespace
     NAME   STATUS   AGE
     naka   Active   71m
     

3. Create Deployment yaml.

   • Create Deployemnt yaml with container image to ghcr.io/nakamasato/fastapi-sample:v1.0.

     kubectl create deploy sample-app --image=ghcr.io/nakamasato/fastapi-sample:v1.0 --dry-run=client -o yaml > sample-app-deployment.yaml
     

   • Set environment variables from ConfigMap.

     envFrom:
       - configMapRef:
           name: sample-app

   • Set environment variable from Secret.

     envFrom:
       ..
       - secretRef:
           name: sample-app

4. Create ConfigMap yaml.

   1. Prepare env.txt.

      MYSQL_HOST=mysql.database.svc.cluster.local
      MYSQL_DATABASE=test_db
      MYSQL_USER=sample_app
      

   2. Create yaml from env.txt.

      kubectl create cm sample-app --from-env-file=env.txt --dry-run=client -o yaml > sample-app-configmap.yaml
      

5. Create Secret yaml.

   kubectl create secret generic sample-app --from-literal=MYSQL_PASSWORD=password --dry-run=client -o yaml > sample-app-secret.yaml
   

6. Apply Deployment, ConfigMap, and Secret.

   kubectl apply -f sample-app-deployment.yaml,sample-app-configmap.yaml,sample-app-secret.yaml -n $namespace
   

   • Check Deployment in your namespace

     kubectl get deploy -n $namespace
     

   • Check Pod in your namespace

     kubectl get pods -n $namespace
     

   • Check ConfigMap in your namespace

     kubectl get cm -n $namespace
     

   • Check Secret in your namespace

     kubectl get secret -n $namespace
     

7. Apply Service.

   kubectl apply -f sample-app-service.yaml -n $namespace
   

   How to create the yaml easily

    kubectl create service clusterip sample-app --tcp=80 --dry-run=client -o yaml > sample-app-service.yaml
   

   • Check the created Service

     kubectl get service -n $namespace
     

   • Check accessibility with kubectl port-forward

     kubectl port-forward svc/sample-app 8080:80 -n $namespace
     

     curl http://localhost:8080/
     {"message":"Hello World"}
     

     http://localhost:8080/docs

     result

     

Clean up resources

kubectl delete -f sample-app-deployment.yaml,sample-app-configmap.yaml,sample-app-secret.yaml,sample-app-service.yaml -n $namespace
kubectl delete -f mysql-deployment.yaml,mysql-service.yaml -n database
kubectl delete ns $namespace
kubectl delete ns database