Using k8s to deploy a MongoDB Database with a Mongo Express web-based Admin interface in aws

Architecture and features:

• The project will be deployed using a kubeadm cluster.
• The MongoDB Database will use Amazon EBS as the persistent storage to store data.

General Concepts

• A Pod is the smallest execution unit in Kubernetes, and an abstraction over containers. A container is a lightweight software that contains all the necessary tools, libraries and code to run an application.

• kubectl exec -it <pod_name> -- /bin/bash to get a bash shell in the container.

• kubectl logs <pod_name> to show information logged by a pod.

• A Deployment is a resource to describe how a ReplicaSet and Pod should behave.

  • kubectl create deploy <deployment_name> --image=<image_name> to create a basic deployment with minimal configurations.
  • kubectl edit deploy <deployment_name> to edit the configuration file of a deployment.
  • kubectl delete deploy <deployment_name> to delete a deployment.

• A ReplicaSet aims to maintain a stable set of Pods running at any given time. The number of Pods maintained is determined in the configuration file of a deployment.

• A Service exposes an application running on a set of Pods as a network service.

• A ConfigMap is used to store non-sensitive data in key-value pairs, and can be consumed as environment variables, command-line arguments, or as configuration files.

• A Secret is similar to a ConfigMap, but more towards storing sensitive data, such as passwords, OAuth tokens, and ssh keys.

  • echo -n '<password>' | base64 to generate a base64 encoded string to be used as password in Secret, though a better hashing algorithm should be used.

Getting Started

1 - Create a Secret, which is used to store sensitive information. The Secret will contain the username and password for MongoDB.

• kubectl apply -f mongodb-secret.yaml to create the Secret called mongodb-pass.
• kubectl delete -f mongodb-secret.yaml to delete the Secret.

2 - Create a StorageClass

• kubectl apply -f mongodb-sc.yaml to create the StorageClass called mongodb-sc.

3 - Create a PersistentVolumeClaim

• kubectl apply -f mongodb-pvc.yaml to create the PersistentVolumeClaim called mongodb-pvc.

4 - Create a Deployment, When deploying MongoDB on Kubernetes, the StorageClass automatically creates a new storage using Amazon Elastic Block Store (EBS) in AWS by provisioning a Persistent Volume (PV).

• kubectl apply -f mongodb-deploy.yaml to create Deploument called mongodb-deploy.

5 - Create Service

• kubectl apply -f mongodb-svc.yaml to create the Service called mongodb-svc.

6 - Create a ConfigMap, which is used to store non-confidential information in key-value pairs. The ConfigMap will contain the mongo database url.

• kubectl apply -f mongodb-cm.yaml to create the Configmap called mongodb-cm.

7 - Create another Deployment . The Deployment will contain a Mongodb-Express Pod, which is a web-based interface to manage MongoDB databases. It will use the username and password from Secret, and the database url from ConfigMap to access the MongoDB internal Service defined in 4.

• kubectl apply -f mongo-express-deploy.yaml to create the Deployment called mongo-express-deploy

8 - create another service

• kubectl apply -f mongo-express-svc.yaml to create the Service called mongo-express-svc