IKO - Lessons Learned (Part 1 - Helm)

The IKO documentation is robust. A single web page, that consists of about 50 actual pages of documentation. For beginners that can be a bit overwhelming. As the saying goes: how do you eat an elephant? One bite at a time. Let's start with the first bite: helm.

What is Helm?

Helm is to Kubernetes what the InterSystems Package Manager (IPM, formerly ObjectScript Package Manager - ZPM) is to IRIS.

It facilitates the installation of applications on the platform - in a fashion suitable for Kubernetes. That's to say that it is developed in such a way to facilitate installation to your needs, whether it be a development, test, or production environment.

We provide on our WRC software distribution all you will need under the IRIS Components tab - it consists of a .tar.gz. Extract it and you will get a .tar. Extract it again and you will see a folder iris_operator_<yourversion>. In here are a README with instructions, as well as 3 folders - an image of the IKO (you could have also got this from the InterSystems Container Registry), chart, and samples. Samples is just to help you form your files but is not actually necessary for IKO installation. Chart, however, is necessary. Let's take a peek.

chart
|
|-> iris-operator
               |
               | -> README.md
               | -> .helmignore
               | -> Chart.yaml
               | -> values.yaml
               | -> templates 
                      | -> _helpers.tpl
                      | -> apiregistration.yaml
                      | -> appcatalog-user-roles.yaml
                      | -> cleaner.yaml
                      | -> cluster-role.yaml
                      | -> cluster-role-binding.yaml
                      | -> deployment.yaml
                      | -> mutating-webhook.yaml
                      | -> NOTES.txt
                      | -> service.yaml
                      | -> service-account.yaml
                      | -> user-roles.yaml
                      | -> validating-webhook.yaml
               

This is the meat and potatoes (a funny way to say basic ingredients) of the application we will be installing. Don't worry. The only thing that we care about is going to be the values.yaml. Everything else is going on behind the scenes, thanks to Helm. Phew! But it's important to know that though our operator may seem like an ordinary pod, it is a lot more than that.

Most of the contents of the values.yaml are also going to be out of the scope of this article because you will not have to worry about them. We will care about just 4 fields (okay, 5 at most).

They are operator.registry, operator.repository, operator.tag, imagePullSecrets.name[0], and imagePullPolicy.

Where is your IKO image? Is your organization using a private repository? Are you planning on pulling from the ICR? Specify your image details in the registry, repository, and tag fields. If you are using the ICR you can leave it as is.

How will you access the ICR, or your organization repository? Assuming it is private you will need to specify your details with which you can access it for pulling. In the next article I touch on how to create this secret, which we can call intersystems-pull-secret instead of the standard dockerhub-secret which is what is presently there if you downloaded the files from the WRC.

Finally for the imagePullPolicy we can leave it as Always, or alternatively change it to IfNotPresent or Never. I'll refer you to the Kubernetes documentation if you need clarification - here. I tend to use IfNotPresent.

Looks like we're good to go (assuming you already have helm installed, if not install it first)! Let's install the IKO. We are going to need to tell helm where the folder with all our goodies is (that's the iris-operator folder you see above). If we were to be sitting at the chart directory you can use the command

helm install intersystems iris-operator

but perhaps you're sitting a little higher. No problem. This is fine too assuming you are sitting in a repository with iris_operator_amd-3.6.7.100:

helm install intersystems iris_operator_amd-3.6.7.100/chart/iris-operator

You'll get a message that the installation was a success and you can double check your deployment is running as is noted by the message and in our docs.

kubectl --namespace=default get deployments -l "release=intersystems, app=iris-operator"

In the next post we'll put the InterSystems Kubernetes Operator to use.