Kubernetes - Part I - Getting Started

After finishing up my last project, I was asked to reverse engineer a bunch of work a departing developer had done on Kubernetes.

Immediately I found Kubernetes a bit of a trick because unlike OpenStack, which has extremely thorough documentation, I found the Kubernetes documentation to be all over the web, in bits and pieces. And most of what I found was "how to" recipes that didn't explain any of the big picture concepts that one normally wants to see before they start 'cooking the recipes'.

So, it took me a while to get focused and make some progress (admittedly, I had some other distractions going on at the time or I might have done this considerably faster). But slowly, I found some good information, and I'll share some of that here.

First, Architecture...

Rather than refer a web link, I am going to refer a youtube link. I have found youtube to be an increasingly valuable place to learn things. Rather than "read", you can kick back on the couch with a beverage of choice, and let some stuff sink in visually. This can be difficult if you're not following along on a laptop or keyboard, but there's some definite merit to "seeing" things visually, or seeing someone do something visually, a la classroom training.

So after watching a number of different youtube videos on Kubernetes, I settled on a couple of these from a gentlemen named Yogesh Mehta. I found THESE videos allowed me to get the thorough understanding of the architecture I needed, and even got a Kubernetes cluster up and running (I did have to fix a few things, which I will comment on).

So the first link is:
https://www.youtube.com/watch?v=o8SpqqKJtFw&t=289s

And this link is entitled:
What is Kubernetes? And what are its Key Components?
 Thanks Yohesh...for asking this fundamental first question and making a video about it.

Next, Building a Cluster....

This link can be found at:
https://www.youtube.com/watch?v=lTyKeNRopqY&t=82s

Here, Yogesh takes you through the process of setting up a very simple cluster, with the following elements:

• Master 
• Node 1
• Node 2

One of the things that Yogesh "brushes over" in this video, is the fact that he installs a "Flannel" network. I found myself asking, "what the hell is a flannel network?"

After all, I'm a Networks guy, and I knew that there had to be some underlying networking in this thing. The Networking is actually one of the most complex and sophisticated aspects of OpenStack (see my posts on this blog regarding Neutron, ML2, OpenvSwitch, et al).

It took me a while, but I finally found a site that lists all of the Kubernetes network plugins, with a description of the distinctions between them.

https://chrislovecnm.com/kubernetes/cni/choosing-a-cni-provider/

It turns out that Flannel seems to be the "default" networking plugin or Container Network Interface (CNI) on just about every setup that I looked at. I wasn't exactly sure why this was the case, how the networking worked, what Flannel brought to the table in terms of features, etc. Now - after reading this site, I was able to get that education.