Getting Started with Kubernetes

Requirements

• Docker-CE
• Minikube

Application Diagram

Deployment

Start the database pod

kubectl apply -f coder.yml

Check Pods and Services

kubectl get services,pods

NAME                         TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
service/coder-database-svc   ClusterIP   10.102.71.253   <none>        5432/TCP         29m
service/coder-server-svc     NodePort    10.101.69.99    <none>        8000:30000/TCP   7s
service/kubernetes           ClusterIP   10.96.0.1       <none>        443/TCP          60m

NAME                        READY   STATUS    RESTARTS   AGE
pod/coder-database-pod      1/1     Running   1          29m
pod/coder-server-rc-7c22x   4/4     Running   4          29m
pod/coder-server-rc-9svfr   4/4     Running   4          29m
pod/coder-webapp-pod        1/1     Running   1          29m

The line containing service/coder-server-svc describe where will be available the load balancing endpoint to be redirected to any pod (Replica 1 or 2). We will be able to acces the server in 10.101.69.99:8000 locally (our computer). For outside we have to use <computer-ip>:30000. If you are running minikube in a virtual machine, then you require to use <virtual-machine-ip>:30000 then, the application will no be available from outside

NAME                         TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
service/coder-server-svc     NodePort    10.101.69.99    <none>        8000:30000/TCP   7s

Initialize Datasabe and Load Sample Data

To load a sample database you need to get into the django container running in the server pod. You can choose between coder-server-rc-7c22x or oder-server-rc-9svfr as both pod's containers are connected to the same database.

kubectl exec -it coder-server-rc-7c22x -c django -- sh

You will be login into the django server. Perform the following command to load the database data.

./manage.py makemigrations
./manage.py migrate
./manage.py loaddata sampledb-compose.json 

Installed 11 object(s) from 1 fixture(s)

Access Django Admin deployed in the Server

The sample database has a default user called coder with password coder1234.

kubectl get services

NAME                 TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
coder-database-svc   ClusterIP   10.102.71.253   <none>        5432/TCP         42m
coder-server-svc     NodePort    10.101.69.99    <none>        8000:30000/TCP   13m

The following Use the following link:

• http://10.101.69.99:8000 (locally)
• http://<virtual-machine-ip>:8000 (work only from host machine)
• http://<computer-ip>:30000 (outside)

Scaling Server Pod

Set the replicas attribute in the 3.coder-server-rc.yml file

nano 3.coder-server-rc.yml

...
spec:
  replicas: 2
...

Apply the changes

kubectl apply -f coder.yml

Acces the the Web Interface

The client side is an Angular 4 applications,i.e., a javascript application inteded to run on the client side. We need to tell the client application how to reach the server. The server pod is running behind the kubernetes service contruct called coder-server-svc.

kubectl get services

NAME                 TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
coder-database-svc   ClusterIP   10.102.71.253   <none>        5432/TCP         42m
coder-server-svc     NodePort    10.101.69.99    <none>        8000:30000/TCP   13m

When you have the service ip address, add a new alias to your /etc/hosts file as follows, indicating where to find the server.

sudo nano /etc/hosts

10.101.69.99	coder_server

Every time you run the kubernetes the IP address could change, so you need to perform this step every kubernetes's pods start/restart.

The client side web page will be available at http://localhost:80