MongoDB and WebApp Deployment Example

This example demonstrates how to deploy a MongoDB instance and a simple web application that connects to the MongoDB database using Kubernetes resources such as Deployments, Services, ConfigMaps, and Secrets.

Overview

The setup consists of:

1. MongoDB Deployment: Deploys a MongoDB instance in a container.
2. WebApp Deployment: Deploys a web application that interacts with the MongoDB instance.
3. ConfigMap: Stores the MongoDB service URL.
4. Secret: Stores sensitive data such as the MongoDB username and password.

Flow Explanation

• A MongoDB deployment is created, exposing the MongoDB service on port 27017.
• A secret is used to securely store the MongoDB username and password.
• The web application is deployed and configured to retrieve MongoDB credentials from the secret and the MongoDB URL from the ConfigMap.
• Both MongoDB and the web application are exposed as services to allow external access.

Files Explanation

1. mongo.yaml

This file defines the MongoDB Deployment and the MongoDB Service.

MongoDB Deployment

• replicas: Sets the number of MongoDB instances to 1.
• image: The Docker image used for MongoDB is mongo:5.0.
• environment variables: The MongoDB root username and password are provided from the secret mongo-secret.

MongoDB Service

• Exposes MongoDB on port 27017 for communication with other pods inside the Kubernetes cluster.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: mongo-deployment
  labels:
    app: mongo
spec:
  replicas: 1
  selector:
    matchLabels:
      app: mongo
  template:
    metadata:
      labels:
        app: mongo
    spec:
      containers:
      - name: mongodb
        image: mongo:5.0
        ports:
        - containerPort: 27017
        env:
        - name: MONGO_INITDB_ROOT_USERNAME
          valueFrom:
            secretKeyRef:
              name: mongo-secret
              key: mongo-user
        - name: MONGO_INITDB_ROOT_PASSWORD
          valueFrom:
            secretKeyRef:
              name: mongo-secret
              key: mongo-password  
---
apiVersion: v1
kind: Service
metadata:
  name: mongo-service
spec:
  selector:
    app: mongo
  ports:
    - protocol: TCP
      port: 27017
      targetPort: 27017

2. mongo-config.yaml

This file defines the ConfigMap for MongoDB. The ConfigMap stores the MongoDB service URL (mongo-service), which is used by the web application to connect to MongoDB.

apiVersion: v1
kind: ConfigMap
metadata:
  name: mongo-config
data:
  mongo-url: mongo-service

3. mongo-secret.yaml

This file defines the Secret that stores the sensitive information (username and password) required for MongoDB.

• The mongo-user and mongo-password are base64 encoded.

apiVersion: v1
kind: Secret
metadata:
  name: mongo-secret
type: Opaque
data:
  mongo-user: bW9uZ291c2Vy  # mongo-user (base64 encoded)
  mongo-password: bW9uZ29wYXNzd29yZA==  # mongo-password (base64 encoded)

4. webapp.yaml

This file defines the WebApp Deployment and the WebApp Service.

WebApp Deployment

• image: Uses a demo web application image.
• environment variables:
  • The MongoDB username and password are sourced from the mongo-secret.
  • The MongoDB URL is sourced from the mongo-config ConfigMap.

WebApp Service

• Exposes the web application on port 3000, with a NodePort of 30100 for external access.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: webapp-deployment
  labels:
    app: webapp
spec:
  replicas: 1
  selector:
    matchLabels:
      app: webapp
  template:
    metadata:
      labels:
        app: webapp
    spec:
      containers:
      - name: webapp
        image: nanajanashia/k8s-demo-app:v1.0
        ports:
        - containerPort: 3000
        env:
        - name: USER_NAME
          valueFrom:
            secretKeyRef:
              name: mongo-secret
              key: mongo-user
        - name: USER_PWD
          valueFrom:
            secretKeyRef:
              name: mongo-secret
              key: mongo-password 
        - name: DB_URL
          valueFrom:
            configMapKeyRef:
              name: mongo-config
              key: mongo-url
---
apiVersion: v1
kind: Service
metadata:
  name: webapp-service
spec:
  type: NodePort
  selector:
    app: webapp
  ports:
    - protocol: TCP
      port: 3000
      targetPort: 3000
      nodePort: 30100

Summary

• MongoDB Deployment (mongo.yaml): Deploys MongoDB using credentials from the secret and exposes it on port 27017.
• ConfigMap (mongo-config.yaml): Stores the MongoDB service URL for use by the web application.
• Secret (mongo-secret.yaml): Stores MongoDB username and password securely.
• WebApp Deployment (webapp.yaml): Deploys the web application, which connects to MongoDB using credentials from the secret and the URL from the ConfigMap. It is accessible externally on port 30100.

This setup provides a simple way to deploy a MongoDB database and a web application in Kubernetes, ensuring secure access using secrets and easy configuration using ConfigMaps.