helm-and-helmsman.md

Helm and Helmsman

Note: this exercise is quite old, and might not work.

This exercise will demonstrate a declarative approach to Helm chart installation using Helmsman.

Prerequisites

This exercise assumes that the following repositories (or forks) have been cloned into a shared folder:

https://github.com/eficode-academy/kubernetes-appdev-katas
https://github.com/eficode-academy/k8s-sentences-sentence
https://github.com/eficode-academy/k8s-sentences-age
https://github.com/eficode-academy/k8s-sentences-name

I.e. listing folders should produce output as follows:

$ ls -l
drwxr-xr-x  6 ubuntu ubuntu 4096 Jan  7 11:36 kubernetes-appdev-katas
drwxr-xr-x  7 ubuntu ubuntu 4096 Jan  7 11:36 k8s-sentences-sentence
drwxr-xr-x  7 ubuntu ubuntu 4096 Jan  7 11:36 k8s-sentences-age
drwxr-xr-x  7 ubuntu ubuntu 4096 Jan  7 11:36 k8s-sentences-name

Use the following commands to clone Praqma repositories or replace with your own forks if possible:

$ cd ~
$ git clone https://github.com/eficode-academy/k8s-sentences-sentence.git
$ git clone https://github.com/eficode-academy/k8s-sentences-age.git
$ git clone https://github.com/eficode-academy/k8s-sentences-name.git

Deploying with Helmsman

Go to the folder which holds our Helmsman specification for the three microservices that make up the sentences application.

$ cd kubernetes-appdev-katas/sentences-app/deploy/helmsman/

The helmsman.yaml file in this folder is an Helmsman desired state file which basically is a declarative specification of the Helm charts we want installed and the parameters we want changed from the defaults.

Specify Target Namespace

Helmsman can create Kubernetes namespaces. We will not use this features, however, Helmsman still need a list of namespaces which we will deploy applications into.

In the helmsman.yaml file the application destination namespace is found in four places. First in the overall list of namespaces (note the trailing ':'):

namespaces:
  default:

and a namespace destination for each microservce - here an example for the age service:

apps:
  age:
    ...
    namespace: default

We want to deploy the sentence application to our own namespace. Investigate the name of your namespace with:

$ kubectl config view | grep namespace

and then modify the helmsman.yaml file to use your namespace (four instances to update).

Deploy the Sentences Application

Deploy the sentences microservices (the three Helm charts) to your namespace with the following command:

$ helmsman -apply -f helmsman.yaml

Since Helmsman waits for resources to be deployed and ready, the command may take a little while to complete.

When Helmsman have deployed the Helm charts, the main service is exposed with a Kubernetes service of type LoadBalancer. Use the following command to get the IP address of that service and test the deployed application.

$ kubectl get services

Upgrade a Microservice of the Sentences Application

The helmsman.yaml file specifies both the Helm chart version for each microservice and values that set both container image repository and tag.

Edit the helmsman.yaml file and change some of the image repositories/tags. E.g. change the image repository to your own repository or use different tags for Praqma images. The following Praqma images have a special observable behavior:

releasepraqma/sentence:1.0-1fee (swaps age and name in the generated sentences)

After modifying the helmsman.yaml, re-run Helmsman to reconcile the application specification with the application deployed to Kubernetes:

$ helmsman -apply -f helmsman.yaml

To see, that Helmsman actually installs Helm charts, use the following command to show installed Helm charts:

$ helm ls

Optional Exercise

The Sentences application was deployed with the frontend service exposed with a Kubernetes service of type LoadBalancer. Update the helmsman.yaml to expose the front-end service using a service of type NodePort instead, upgrade the deployment and test access to the sentences application using the nodeport service.

Cleanup

Delete the application installed with Helmsman:

$ helmsman -destroy -f helmsman.yaml