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Exercise - Deploy MongoDB

In this lab, you'll deploy MongoDB to the Azure Kubernetes Service (AKS) cluster using Helm. You'll also see how to use a Kubernetes secret to store the MongoDB connection username and password.

Helm is an application package manager for Kubernetes such as apt or yum package managers, and a way to easily deploy applications and services into Kubernetes, via what are called charts. To use Helm you will need the helm command

This is already installed if you're using the Azure Cloud Shell.

Prerequisites

Lab overview

Architecture Diagram

Tools

  • Use Helm and a standard provided Helm chart to deploy MongoDB.

  • Be careful with the authentication settings when creating MongoDB. It is recommended that you create a standalone username/password. The username and password can be anything you like, but make a note of them for the next task.

    Important: If you need to delete the Helm deployment and start over, make sure you delete the Persistent Volume Claims created otherwise you'll run into issues with authentication due to stale configuration. Find those claims using kubectl get pvc and use kubectl delete pvc <pvc-name>.

    Helm will instal Persistent Volume with delete reclaim policy. So if you delete the persistent volume claim, it deletes persistent volume as well

Configure the Helm client to use stable repository

  1. Add bitnami repositories to helm

    Helm version 3 does not come with any repositories predefined, so you’ll need initialize the stable chart repository.

    Add the stable Helm charts repository

    helm repo add bitnami https://charts.bitnami.com/bitnami

    Once this is installed, you will be able to list the charts you can install:

    helm search repo bitnami

    For update the repository use

    helm repo update

  2. Deploy an instance of MongoDB to your cluster

    You're now ready to install the MonogoDB instance. Recall from earlier, that you configured your cluster with a ratingsapp namespace. You'll specify the namespace as part of the helm install command, and a name for the database release. The release is called ratings and is deployed into the ratingsapp namespace.

    Note The application expects a database named ratingsdb. Using a different database name will cause the application to fail!

    Initialize MongoDB with helm charts

    helm install ratings bitnami/mongodb \
    --namespace ratingsapp \
    --set auth.username="ratings-user",auth.password="ratings-password",auth.database=ratingsdb

Create a Kubernetes secret to hold the MongoDB details

  1. Create secret

    Kubernetes has a concept of secrets. Secrets let you store and manage sensitive information, such as passwords. Putting this information in a secret is safer and more flexible than hard coding it in a pod definition or a container image.

    Kubernetes stores secrets in base64 format

    • A Kubernetes secret can hold several items and is indexed by a key. In this case, the secret contains only one key, called MONGOCONNECTION. The value is the constructed connection string from the previous step. Replace and with the ones you used when you created the database.

    • All services in Kubernetes get DNS names via kube-dns. You can use the fully qualified form servicename.namespace.svc.cluster.local In this demo it will be, ratings-mongodb.ratingsapp.svc.cluster.local

    To create a secret:

    kubectl create secret generic mongosecret \
    --namespace ratingsapp \
    --from-literal=MONGOCONNECTION="mongodb://ratings-user:[email protected]:27017/ratingsdb"

    Note: Helm chart may have installed another secret named ratings-mongodb. If its installed just delete it.

    kubectl delete secret ratings-mongodb -n ratingsapp

    --from-literal parameter allows you to provide the secret values directly on the command in plain text. Another way is provide values from file via using --from-file command.

    You will need to reference this secret when configuring Ratings API later on.

  2. Run the kubectl describe secret command to validate that the secret.

    kubectl describe secret mongosecret --namespace ratingsapp

Summary

In this exercise, you configured the Helm stable repository, then used a Helm chart to deploy MongoDB to your cluster. You then created a Kubernetes secret to hold database credentials.

Next, you'll deploy the Fruit Smoothies ratings-api to your AKS cluster.

Next Lab: Exercise - Deploy the ratings API

Docs / References