Part II – Kubernetes DevOps : Introduction to Helm

This is the second post in a multi-part blog series on Kubernetes DevOps using Azure. I am co-authoring this series with the help of my colleague at Microsoft, Daniel Selman. We recently worked on the Kubernetes project together and thought to share our learnings.

In the last post, you got to better understand the application that was going to be deployed in the Kubernetes cluster. In this post, you will learn about the tool called “Helm”.

Part I: Introduction to the Historic Events Microservice
Part II: Getting started with Helm
Part III: VSTS Build (Helm package + containerization of application)
Part IV: VSTS Release (using Helm)
Part V: Lessons Learned – When things go wrong!

So what is Helm?

Do you know how all things Kubernetes are named after nautical terms? This really isn’t any different.
Helm is a package manager for Kubernetes and is analogous to Apt-Get for Linux environments. It is made up of two components: Tiller which is the server-side component, and Helm which is the client-side component. Helm packages are known as charts and by default use a public chart repository. However, they can be configured to use a private repository (like Azure blob storage). Helm charts are written in a mix of YAML and Go Templating Syntax.

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Source: https://www.slideshare.net/alexLM/helm-application-deployment-management-for-kubernetes

Helm can be used to empower your dev-ops workflows in two distinct ways. First, it allows for the parameterization of YAML files for K8s deployments. This means that many people can utilize YAML from a shared source without modifying the file itself. Instead, they can pass their individual values at runtime (e.g. a username for a configmap).
For example, to deploy and configure the MySQL Helm Chart you would run the following command:

helm install --name my-release stable/mysql

No more diving into the YAML to get your deployment up and running. Pretty convenient right?

Second, it provides a standardized way of distributing and implementing all the associated YAML for an application. Microservices are cool (minimizing dependencies makes everyone’s lives easier), but they also result in many different containers being necessary to get an application running. Kubernetes augments this sprawl by introducing additional constructs that need to be defined (services, configmaps, secrets). As a result, even basic three tier applications can require almost a dozen k8s constructs (and likely a dozen different YAML files). Even someone who knows the application like the back of their hand likely wouldn’t know how and in what order to deploy these different files.

Helm handles that for you!.

Instead of running a dozen commands to deploy the different components of your application, you throw all your YAML into the templates folder of your chart (we’ll get to that later) and Helm will handle it for you.

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Quick note on the YAML we’re working with

A previous blog post went through the process of containerizing our history application. The purpose of this blog is to cover the helm piece of the puzzle but to give you an idea of what we are starting with from a vanilla YAML perspective.
We’ve got four files total for the application- asp-web-dep, asp-web-svc, node-api-dep, node api-svc. All of the containers are being pulled from the Azure Container Registry. I’ll include the four files here for reference.

asp-web-dep.yaml

apiVersion: apps/v1beta1
kind: Deployment
metadata:
  name: aspcoreweb-dep
spec:
  replicas: 1
  template:
    metadata:
      labels:
        app: aspcoreweb
        tier: frontend
        track: stable
    spec:
      containers:
        - name: demowebapp
          image: "rzdockerregistry.azurecr.io/aspcoreweb:BuildNumber"
          ports:
            - name: http
              containerPort: 80
      imagePullSecrets:
        - name: sec

asp-web-svc.yaml

kind: Service
apiVersion: v1
metadata:
  name: aspcoreweb-svc
spec:
  selector:
    app: aspcoreweb
    tier: frontend
  ports:
    - protocol: "TCP"
      port: 80
      targetPort: 80
  type: LoadBalancer

node-api-dep.yaml

kind: Deployment
metadata:
  name: nodeapi-dep
spec:
  replicas: 2
  template:
    metadata:
      labels:
        app: nodeapi
        tier: backend
        track: stable
    spec:
      containers:
        - name: nodeapi
          image: "rzdockerregistry.azurecr.io/nodeapi:BuildNumber"
          env:
            - name: url
              value: https://rzshared.blob.core.windows.net/data
          ports:
            - name: http
              containerPort: 8080
      imagePullSecrets:
        - name: sec

node-api-svc.yaml

kind: Service
apiVersion: v1
metadata:
  name: nodeapi-dep
spec:
  selector:
    app: nodeapi
    tier: backend
  ports:
    - protocol: TCP
      port: 8080
      targetPort: 8080

Lets make a chart

If you haven’t yet, get kubectl and helm installed on your machine and have your kubectl configured to point at a Kubernetes Cluster (we’ll be using AKS, which you can get started with here). Helm uses your kube config so it should play nice with your cluster out of the box.
Helm at the time of writing this requires Tiller, the server-side component. Run the following command to initialize tiller on your cluster:

	helm init	

Next, let’s scaffold a chart. When you run a simple Helm create [name] command it will create a basic Nginx chart, which we will replace with the components of our application. First, run the helm create command:

helm create [chart_name]

This will create a new directory with all the elements of the helm chart.

This blog isn’t going to cover all the elements of a Helm chart, but instead focus the templates folder and the values.yaml file. The templates folder is where your YAML will be placed. Its currently populated by the nginx files, so you’ll want to delete all of the content in this folder and replace it with the yaml for your application.

Similarly, delete the content (not the file) of values.yaml. Let’s start from a blank slate and replace it with the following values. The buildNumber will be used later on for the VSTS Pipeline and the imagePullSecret will be used to specify the… well imagePullSecret. Don’t worry about the specific values as these can be updated later on.

buildNumber: BuildNumber
imagePullSecret: acr 

We will make one modification to the YAML files, however. Under the hood, helm has a “Release” object which contains information about the deployment of the helm chart. Specifically, release.name provides a unique identifier for your chart so that you can deploy one chart many times to a cluster without errors associated with overlapping names. We’ve added in a reference to the release name attribute in each of the yaml files as such:

  name: {{ .Release.Name }}-aspcoreweb-dep
  name: {{ .Release.Name }}-aspcoreweb-svc
  name: {{ .Release.Name }}-nodeapi-dep
  name: {{ .Release.Name }}-nodeapi-dep

Lets recap. We’ve initialized tiller on our cluster, scaffolded a helm chart, and threw our (mostly) vanilla YAML files in the templates folder.
Our last step is to package it up for ease of distribution. Navigate to the directory base directory of your helm chart and run the following command:

 helm package

Now your chart can be distributed and installed on your cluster using helm install:

helm install [chart_name]

Now that we have some familiarity with the application, Kubernetes, and helm, we are going to transition to VSTS to handle the Build and Release process from code to chart deployment over the next few blog posts, so make sure to check back as we continue this series.

Part I – Kubernetes DevOps : Introduction to the Historic Events Microservice

This is the first post in a multi-part blog series on Kubernetes DevOps using Azure. I am co-authoring this series with the help of my colleague at Microsoft, Daniel Selman. We recently worked on the Kubernetes project together and thought to share out learnings.

Anyways, below is a high-level structure of the blog posts we are planning to publish:

Part I: Introduction to the Historic Events Microservice
Part II: Getting started with Helm
Part III: VSTS Build (Helm package + containerization of application)
Part IV: VSTS Release (using Helm)
Part V: Lessons Learned – When things go wrong!

We do assume that you have basic knowledge of K8s and Docker containers, as we don’t really cover the basics of either of those in this blog series.

Software/Services

Following is the list of software you want to install on your machine.

• Kubectl
• Helm
• Docker
• Minikube (optional, only needed for local testing)
• Git
• Azure CLI

If you like to use a script to install this software on a Linux VM (tested on Ubuntu 16.04), you can download it here: https://github.com/razi-rais/microservices/blob/master/reference-material/install-k8s-lab-software.sh

On the services side, we will be using Azure AKS and VSTS. In case you don’t have Azure subscription you can get yourself Azure trial for free here: https://azure.microsoft.com/en-us/offers/ms-azr-0044p

Alright, so for the demonstration purposes, we have created a simple Historic Events microservice. We thought it won’t hurt to throw some history while working on modern technologies!

Overview

From a technical perspective, we have a microservice that serves the UI which is written in ASP.NET Core 2.0. It pulls data by talking to various RESTful endpoints exposed by Node JS API that is served by another microservice. The actual content storing the details about historic
events), that is served by API is stored in various JSON files, that are persisted as a blog on Azure Storage.
In a nutshell, from an end user standpoint the web app home page looks like below:

image001

When a user wants to learn more about a particular historic event, they can either select particular historic event from the top menu, or they can simply click on the description of a particular event provided on the home page.

For example, the French Revolution event page is shown below. All event details pages follow similar table based layout to list critical events.

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Code Walkthrough

The code and all relevant artifacts are available on GitHub: https://github.com/razi-rais/aks-helm-sample

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This is a plain vanilla ASP.NET Core 2.0 web application.

HistoricEvent (https://github.com/razi-rais/aks-helm-sample/blob/master/aspcoreweb/Controllers/Event.cs#L8) define a basic entity, that represents an event object. The actual attributes are date and description of historic event.

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Most of the actual work happens inside the HomeConroller, which provides methods to connect to backend api service and fetch the data.

The GetEvent (https://github.com/razi-rais/aks-helm-sample/blob/master/aspcoreweb/Controllers/HomeController.cs#L38) method takes a url of an endpoint as a parameter. It then connects to the url endpoint and read the content as a string asynchronously but ultimately converting it into JSON objects stored in a List of type HistoricEvent. Finally, it returns the List object containing all the events.

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If you are wondering who call GetEvent it is inside the method called Event. (https://github.com/razi-rais/aks-helm-sample/blob/master/aspcoreweb/Controllers/HomeController.cs#L54)

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The is basically an action tied to the View. The parameter id essentially acts as a key referring to the event we are interested to fetch from the backend service (e.g. ww2, ww1 etc). The method itself is trivial and we have left most of the optimization out. It does the bare minimum at the moment of printing on the console which endpoint its going to connect and port at the moment is set to 8080. Finally, it calls GetEvent to return the HistoricEvent objects stored in the List and send them back as a View.

The Event.cshtml (https://github.com/razi-rais/aks-helm-sample/blob/master/aspcoreweb/Views/Home/Event.cshtml) View presents the list of events in a table format.

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Data Api (NodeJS)

The backend service code is placed inside NodeJSApi folder
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The server.js runs the server that listens to port 8080.
Since the actual files containing the event data are stored on Azure Blob Storage, we set the URL variable to the blob storage endpoint, which is passed through an environment variable.

Let’s take a look at the endpoint that returns ww1 (World War 1) related events (https://github.com/razi-rais/aks-helm-sample/blob/master/nodejsapi/server.js#L22). First, it connects to the URL, which points to the Azure Blob file e.g. (https://name. blob.core.windows.net/data/ww1) and then it reads the relevant JSON file (e.g. ww1.json). We do check to see if the status is 200, meaning the file is pulled from the blob, in which case the content of the response is set to the JSON.

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Historic Events JSON Files

All the data related to various historic events is available in the JSON file format. You can find the link of each of the historic event JSON file below.

 

NOTE: Azure blob storage requires file names to be in the lower case.

 

Name Description URL
frenchrevolution French Revolution https://github.com/razi-rais/aks-helm-sample/blob/master/data/frenchrevolution.json
renaissance Renaissance https://github.com/razi-rais/aks-helm-sample/blob/master/data/renaissance.json
ww1 World War I https://github.com/razi-rais/aks-helm-sample/blob/master/data/ww1.json
ww2 World War II https://github.com/razi-rais/aks-helm-sample/blob/master/data/ww2.json

Docker Files

Both the front end and back end service are packaged as Docker Linux container image.

1. Frontend UI: https://github.com/razi-rais/aks-helm-sample/blob/master/aspcoreweb/Dockerfile

2. Backend API: https://github.com/razi-rais/aks-helm-sample/blob/master/nodejsapi/Dockerfile