kubernetes-multi-app

Kubernetes Deployment

Table of contents

• Add postgres & adminer
  • postgres
  • adminer
• Add kanban
• Add & config Ingress
  • Add Ingress
  • Routing config of Ingress Controller
• Testing application
  • Adminer App
  • Kanban App
• References

Add postgres & adminer

postgres

First create PeristentVolumeClaim using postgres-pvc.yaml file. And then apply it:

$ kubectl apply -f postgres-pvc.yaml
persistentvolumeclaim/postgres-persistent-volume-claim created

$ kubectl get pvc
NAME                               STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
postgres-persistent-volume-claim   Bound    pvc-f5d9b781-9cdf-4a4c-8c9b-2edb8330d139   4Gi        RWO            standard       10s

Next create a ConfigMap that will hold all database credentials - postgres-configmap.yaml:

$ kubectl apply -f postgres-config.yaml
configmap/postgres-config created

$ kubectl get configmaps
NAME              DATA   AGE
postgres-config   3      11s

Then create a new file for Deployment - postgres-deployment.yaml and then apply it:

$ kubectl apply -f postgres-deployment.yaml
deployment.apps/postgres created

$ kubectl get deployments
NAME       READY   UP-TO-DATE   AVAILABLE   AGE
postgres   1/1     1            1           5m6s

And finally we need to expose pods from this Deployment to other pods inside this cluster using ClusterIP Service - postgres-svc.yaml:

$ kubectl apply -f postgres-svc.yaml
service/postgres created

$ kubectl get svc
NAME         TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)    AGE
kubernetes   ClusterIP   10.96.0.1       <none>        443/TCP    8m35s
postgres     ClusterIP   10.109.98.250   <none>        5432/TCP   4m34s

adminer

Postgres is set up (but it can't be accessable by any other service inside or outside cluster yet). So let's move on to adminer.

Similar story here, first we need to create a Deployment (adminer-deployment.yaml) & Service (adminer-svc.yaml) for adminer and both of them apply using kubectl apply -f command.

$ kubectl apply -f adminer-deployment.yaml
deployment.apps/adminer created

$ kubectl apply -f adminer-svc.yaml
service/adminer created

To check if all your Pods and Deplyments are ok you can type:

$ kubectl get pods
NAME                       READY   STATUS    RESTARTS   AGE
adminer-6f9fd8d895-jqjpb   1/1     Running   0          7m14s
postgres-8ff946f87-z4bzn   1/1     Running   0          9m15s

$ kubectl get deployments
NAME       READY   UP-TO-DATE   AVAILABLE   AGE
adminer    1/1     1            1           7m41s
postgres   1/1     1            1           9m42s

Add kanban

First kanban-app-deployment.yaml file has beed created. Then inside a terminal use following command:

$ kubectl apply -f kanban-app-deployment.yaml
deployment.apps/kanban-app-deployment created

Now to check if Pod & Deployment has been created:

$ kubectl get pods
NAME                                     READY   STATUS             RESTARTS   AGE
kanban-app-deployment-67445565b8-vplbq   0/1     CrashLoopBackOff   3          2m10s

$ kubectl get deployments
NAME                    READY   UP-TO-DATE   AVAILABLE   AGE
kanban-app-deployment   0/1     1            0           2m56s

Add & config Ingress

Add Ingress

To get inside the application you need to set up Ingress which is a gateway to a cluster - the only way you can enter any application inside of it.

Community implementation of Ingress: https://github.com/kubernetes/ingress-nginx

Article about Ingress: https://www.joyfulbikeshedding.com/blog/2018-03-26-studying-the-kubernetes-ingress-system.html

Accordingly to an official website documentation first we need to run following command in order to install Ingress:

$ kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/nginx-0.30.0/deploy/static/mandatory.yaml
namespace/ingress-nginx created
configmap/nginx-configuration created
configmap/tcp-services created
configmap/udp-services created
serviceaccount/nginx-ingress-serviceaccount created
clusterrole.rbac.authorization.k8s.io/nginx-ingress-clusterrole created
role.rbac.authorization.k8s.io/nginx-ingress-role created
rolebinding.rbac.authorization.k8s.io/nginx-ingress-role-nisa-binding created
clusterrolebinding.rbac.authorization.k8s.io/nginx-ingress-clusterrole-nisa-binding created
deployment.apps/nginx-ingress-controller created
limitrange/ingress-nginx created

For simplicity, I've downloaded above file and save it as ingress-nginx.yaml.

Next, we need to run another command to enable Ingress addon:

$ minikube addons enable ingress
🌟  The 'ingress' addon is enabled

Routing config of Ingress Controller

Now we need to set up some routing rules for Ingress controller. Therefore the ingress-controller.yaml file has been created and applied:

$ kubectl apply -f ingress-controller.yaml
ingress.networking.k8s.io/ingress-controller created

Testing application

Adminer App

It's available under the URL http://adminer.k8s.com and the credentials are:

System: PostgreSQL
Server: postgres
Username: kanban
Password: kanban
Database: kanban

After that you should be login to the database.

If you want to change the default design of an adminer you can specify it in the adminer-deployment.yaml file in the spec.template.spec.containers[0].env[0] where you can change a value of ADMINER_DESIGN variable from pepa-linha to whatever you want (full list available in the GitHub project):

apiVersion: apps/v1
kind: Deployment
metadata:
  name: adminer
spec:
  template:
    spec:
      containers:
          env:
            - name: ADMINER_DESIGN
              value: pepa-linha

Kanban App

The UI is available under the address http://kanban.k8s.com.

If you want to connect directly to the backend you need to append above URL with /api/ prefix, e.g. http://kanban.k8s.com/api/swagger-ui.html.

References

• Kubernetes - Multi Apps, Helm & Helmfile https://github.com/wkrzywiec/k8s-helm-helmfile

• kubectl overview https://kubernetes.io/docs/reference/kubectl/overview/

• kubectl create vs kubectl apply https://stackoverflow.com/questions/47369351/kubectl-apply-vs-kubectl-create

• Minikube https://kubernetes.io/docs/setup/learning-environment/minikube/

• Ingress Controllers https://kubernetes.io/docs/concepts/services-networking/ingress-controllers/

• PostgreSQL in Kubernetes https://severalnines.com/database-blog/using-kubernetes-deploy-postgresql

• Adminer Docker https://hub.docker.com/_/adminer/