Most asked technical questions in the #l3_container_ochestration channel of the Suse Cloud Native Scholarship
Q. On the Kubeconfig concept I'm following the second video where kind is used, but I'm executing all the kubectl commands against previously created (with k3s) kubernetes inside the vagrant VM. There is a curious difference - the roles of the created nodes are different: the ones created by k3s has both control-plane and master roles, but the one created by kind has only master role. Does anybody know why it's so? Is control-plane some unnecessary part of kubernetes? - Evgeniia.Vakarina
A. The control-plane is the core part of Kubernetes. It runs on the master node.
I’m not that familiar with Kind but it looks like it outputs the role in the same was as k3s:
kube-control-plane Ready control-plane,master 2m14s v1.20.2
I wouldn’t read too much into the output though. Essentially it’s telling you that it’s the one in charge and not a worker node. - ian.young.gg
I. Hey, I just formed up this on my own so wanted to share it. For people who have completed L3 (Container Orchestration) and previous lessons and want to know how might this philosophy of Docker and Kubernetes be applied in code when you're developing your own applications and how will we use it to create micro-services and how does it makes it so easy and better!So first things first let's create a scenario say you're creating an application, a rather simple application that allows users to create a post, comment on a post, query for posts, and moderate posts.
So we generally divide these into their own services:
Service A: Controls Posts
Service B: Controls CommentsWe don't need services for querying and moderating posts and comments since they can be implemented in their own respective services (also creating a separate service for them will introduce dependency). But here we encounter a huge problem; since Service B controls comments how will it know that the post the user's commenting in exists or not?This is where we introduce Service C: Event Bus; it is a global bus that is immutable and does not contain data but rather the only thing it does is to emit events, say it emits a post created event and Service B now recognizes that a post is created and saves its reference and vice versa (the problem is solved since the post existence can be verified).
So now the basic structure of our application is done, if a user now does a CRUD request on posts or comments they can be passed onto the services that require them with the help of event bus.Now that is scenario is clear we can come to the deployment (here docker and kubernetes will come into play),
What is the problem that we face right now? Now these services are working separately on their own but how will they communicate? And if we deploy them all together what about scaling? That's we introduced Docker! Rather than having these services run on separate virtual machines we can make them run on Docker containers.So now we can control when we need a service and when not, say we see too much traffic on post service we can create more Docker containers running the Post Service to handle them.
But now we face another problem how will these services talk to the Event Bus? Even if they know the IP of the Event Bus and try to contact it directly it will be a waste since that would become too much hard-coded.This is the exact place where Kubernetes comes, kubernetes hosts these containers on each nodes of its workers (it was also mentioned in the course it is a good practice to keep the ratio between containers and pods one-to-one), not only that but now we can deploy services and Ingress more specifically a Load Balancer that will take care of the rest where, when, and how to contact the Event Bus and will pass that on to the worker nodes (the currently running pods for the event bus).And that is how the entire thing clicks together! Thank you Kubernetes! - frostzt
Q.
What's the package manager for the version of Linux running in the vagrant box? apt-get and yum don't seem to work -Calistus.Igwilo
A. zypper -george.udoyen
Q. Has anyone faced issues with deploying kubernetes cluster using k3s on on-prem server running on CentOS?It does not recognize the kubectl command, I even configured the environment variable... -Mian.Mansoor.Ahmad
A. @Ajna.Toth Thank you, It worked using Selinux customization and then custom installation using: https://kubernetes.io/docs/tasks/tools/install-kubectl-linux/