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Feedback: Basics of Kubernetes

Posts: 6
in LFS258 Class Forum

Dear course team,

The section "Challenges" in this first part of the course has a couple of sentences that seem incomplete.

"Rolling updates and easy rollbacks of containers is an important feature, and eventually tear down the resource when no longer needed." > The rolling updates and easy rollbacks are the subject of the first clause, but not the subject of the second, so this is probably intended to say something like "as well as the ability to eventually tear down..."

"As containers are launched on any worker node, the network must join the resource to other containers, while still keeping the traffic secure from others."

I think this sentence is rather unclear. I can see why at this stage the writer didn't want to be specific and say something like "the network should establish communication between a container and others in the same pod, as well as proxy requests to any service it's a part of", but it seems like it would be better to phrase it in a way that indicates the cluster establishes networking between a new container and the resources it relies on to function properly, while keeping logical isolation between unrelated services.

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Comments

  • Posts: 6

    "The Cloud Foundry Foundation embraces the 12 factor application principles. These principles provide great guidance to build web applications that can scale easily, can be deployed in the cloud, and whose build is automated. Borg and Kubernetes address these principles as well."

    I hadn't come across the 12 factor principles referred to here, but googling it finds me https://12factor.net/, written it seems by Heroku developers. Perhaps provide a link or mention Heroku to credit them?

  • Posts: 6
    edited September 2024

    There is a typo in this image: https://d36ai2hkxl16us.cloudfront.net/course-uploads/e0df7fbf-a057-42af-8a1f-590912be5460/j0i2uejk3hr5-Kubernetes_Architecture.png

    s/contol/control

    The explanatory text for it mentions "Not all components are shown. Every node running a container would have kubelet and kube-proxy, for example.", when in fact the image does show a running instance of kube-proxy and kubelet process on the 3 worker nodes and the control plane. I'm not sure if there is some nuance I'm missing here or if the image has changed but text not been updated accordingly.

  • Posts: 6

    "Orchestration is managed through a series of watch-loops, also called controllers or operators. Each controller interrogates the kube-apiserver for a particular object state, then modifying the object until the declared state matches the current state. These controllers are compiled into the kube-controller-manager, but others can be added using custom resource definitions."

    Question this leaves me with: does this mean that the kube-controller-manager consists of a core set of controllers shipped with Kubernetes itself, and any others added by CRD later will not be considered part of the kube-controller-manager? If so I think it would be useful to instead of saying "These controllers" to say "Controllers that are part of Kubernetes core[...]".

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