Deploy an Express/MongoDB Application on k8s

Before reading through this, you may want to read the page about the application being deployed on the Build an Express App that uses MongoDB page

Contents

Prerequisites

  • Docker
  • Minicube
  • Minikube k8s cluster
  • kubectl installed
  • Helm and Tiller

Installation

Minikube

Hyper-V

Using minikube with Windows requires us to use Hyper-V as a driver, we can follow the instructions on Jock Reed's Blog on how configure a new virtual switch, then we can start minikube using this switch as follows:

minikube start --vm-driver hyperv --hyperv-virtual-switch "Primary Virtual Switch"

After which point we can stop minikube

minikube stop

Enable Dynamic Memory from Hyper-V Manager, and then start minikube with:

minikube start 

VirtualBox

We can use VirtualBox as our driver as well with the following

minikbe start --vm-driver virtualbox

Running Minikube

minikube start

Note that this may download some files which will take a while, but you will eventually see the following output

Starting local Kubernetes v1.10.0 cluster...
Starting VM...
Downloading Minikube ISO
 178.87 MB / 178.87 MB [============================================] 100.00% 0s
Getting VM IP address...
E1215 14:28:43.740427    9968 start.go:210] Error parsing version semver:  Version string empty
Moving files into cluster...
Downloading kubelet v1.10.0
Downloading kubeadm v1.10.0
Finished Downloading kubeadm v1.10.0
Finished Downloading kubelet v1.10.0
Setting up certs...
Connecting to cluster...
Setting up kubeconfig...
Stopping extra container runtimes...
Starting cluster components...
Verifying kubelet health ...
Verifying apiserver health ...Kubectl is now configured to use the cluster.
Loading cached images from config file.


Everything looks great. Please enjoy minikube!

Next we can view our minikube dashboard with

minikube dashboard

Creating a Deployment

We can create a deployment based on a deployment yaml file

For the purpose of this, we will make use of the deployment configurations that are defined in the Build an Express App that uses MongoDB at the Comments App GitHub Repository

To see how the app is constructed and how it communicates with the DB, read the page on Building an Express App that uses Mongo

The Express App is exposed on port 8080 and will speak to the Mongo instance on mongo:27017

Building the Image

Before we can deploy our application we need to build it as a Docker image and push it to a repository, in the case of the Comments App, this will be as follows

From the application directory run

docker build -t <USERNAME>/comments-app
docker push

If we do not wish to redeploy our

Deploying on Kubernetes

Once logged into a kubernetes cluster we can make use of the express.yaml to deploy the express app, and the mongo.yaml file to deploy Mongo

kubectl create -f express.yaml
kubectl create -f mongo.yaml

This will create a deployment as well as a service for both the Express App and Mongo. The deployment configs are as follows

express.yaml

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  annotations:
    deployment.kubernetes.io/revision: "1"
  labels:
    app: comments-app
  name: comments-app
spec:
  replicas: 1
  selector:
    matchLabels:
      app: comments-app
  template:
    metadata:
      labels:
        app: comments-app
      name: comments-app
    spec:
      containers:
      - image: <USERNAME>/comments-app
        imagePullPolicy: Always
        name: comments-app

---
apiVersion: v1
kind: Service
metadata:
  labels:
    app: comments-app
  name: comments-app
spec:
  ports:
  - name: tcp-8080-8080-comments-app
    nodePort: 30016
    port: 8080
    protocol: TCP
    targetPort: 8080
  selector:
    app: comments-app
  type: LoadBalancer

mongo.yaml

apiVersion: v1
kind: Service
metadata:
   name: mongo
   labels:
     run: mongo
spec:
   ports:
   - port: 27017
     targetPort: 27017
     protocol: TCP
   selector:
     run: mongo

---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
   name: mongo
spec:
   template:
     metadata:
       labels:
         run: mongo
     spec:
       containers:
       - name: mongo
         image: mongo
         ports:
         - containerPort: 27017

Use the App

We can use minikube to View the application

minikube service comments-app

Once on the app we can create a comment, which will take us to the comments view page. When creating a comment a new record is inserted into Mongo, and when viewing them all existing comments are retrieved and displayed